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Osugi A, Kojima M, Takebayashi Y, Ueda N, Kiba T, Sakakibara H. Systemic transport of trans-zeatin and its precursor have differing roles in Arabidopsis shoots. NATURE PLANTS 2017; 3:17112. [PMID: 28737742 DOI: 10.1038/nplants.2017.112] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 06/19/2017] [Indexed: 05/20/2023]
Abstract
Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots1,2. Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action3-5. Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.
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Affiliation(s)
- Asami Osugi
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
- Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Mikiko Kojima
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Yumiko Takebayashi
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Nanae Ueda
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Takatoshi Kiba
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
| | - Hitoshi Sakakibara
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
- Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
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Yang ZB, Liu G, Liu J, Zhang B, Meng W, Müller B, Hayashi KI, Zhang X, Zhao Z, De Smet I, Ding Z. Synergistic action of auxin and cytokinin mediates aluminum-induced root growth inhibition in Arabidopsis. EMBO Rep 2017; 18:1213-1230. [PMID: 28600354 DOI: 10.15252/embr.201643806] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/27/2017] [Accepted: 05/02/2017] [Indexed: 11/09/2022] Open
Abstract
Auxin acts synergistically with cytokinin to control the shoot stem-cell niche, while both hormones act antagonistically to maintain the root meristem. In aluminum (Al) stress-induced root growth inhibition, auxin plays an important role. However, the role of cytokinin in this process is not well understood. In this study, we show that cytokinin enhances root growth inhibition under stress by mediating Al-induced auxin signaling. Al stress triggers a local cytokinin response in the root-apex transition zone (TZ) that depends on IPTs, which encode adenosine phosphate isopentenyltransferases and regulate cytokinin biosynthesis. IPTs are up-regulated specifically in the root-apex TZ in response to Al stress and promote local cytokinin biosynthesis and inhibition of root growth. The process of root growth inhibition is also controlled by ethylene signaling which acts upstream of auxin. In summary, different from the situation in the root meristem, auxin acts with cytokinin in a synergistic way to mediate aluminum-induced root growth inhibition in Arabidopsis.
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Affiliation(s)
- Zhong-Bao Yang
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan, China
| | - Guangchao Liu
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan, China
| | - Jiajia Liu
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan, China
| | - Bing Zhang
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan, China
| | - Wenjing Meng
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, China
| | - Bruno Müller
- Institute of Plant Biology, University of Zurich, Zurich, Switzerland
| | - Ken-Ichiro Hayashi
- Department of Biochemistry, Okayama University of Science, Okayama, Japan
| | - Xiansheng Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, China
| | - Zhong Zhao
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Ive De Smet
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.,VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Zhaojun Ding
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, College of Life Science, Shandong University, Jinan, China
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53
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Spallek T, Melnyk CW, Wakatake T, Zhang J, Sakamoto Y, Kiba T, Yoshida S, Matsunaga S, Sakakibara H, Shirasu K. Interspecies hormonal control of host root morphology by parasitic plants. Proc Natl Acad Sci U S A 2017; 114:5283-5288. [PMID: 28461500 PMCID: PMC5441792 DOI: 10.1073/pnas.1619078114] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Parasitic plants share a common anatomical feature, the haustorium. Haustoria enable both infection and nutrient transfer, which often leads to growth penalties for host plants and yield reduction in crop species. Haustoria also reciprocally transfer substances, such as RNA and proteins, from parasite to host, but the biological relevance for such movement remains unknown. Here, we studied such interspecies transport by using the hemiparasitic plant Phtheirospermum japonicum during infection of Arabidopsis thaliana Tracer experiments revealed a rapid and efficient transfer of carboxyfluorescein diacetate (CFDA) from host to parasite upon formation of vascular connections. In addition, Phtheirospermum induced hypertrophy in host roots at the site of infection, a form of enhanced secondary growth that is commonly observed during various parasitic plant-host interactions. The plant hormone cytokinin is important for secondary growth, and we observed increases in cytokinin and its response during infection in both host and parasite. Phtheirospermum-induced host hypertrophy required cytokinin signaling genes (AHK3,4) but not cytokinin biosynthesis genes (IPT1,3,5,7) in the host. Furthermore, expression of a cytokinin-degrading enzyme in Phtheirospermum prevented host hypertrophy. Wild-type hosts with hypertrophy were smaller than ahk3,4 mutant hosts resistant to hypertrophy, suggesting hypertrophy improves the efficiency of parasitism. Taken together, these results demonstrate that the interspecies movement of a parasite-derived hormone modified both host root morphology and fitness. Several microbial and animal plant pathogens use cytokinins during infections, highlighting the central role of this growth hormone during the establishment of plant diseases and revealing a common strategy for parasite infections of plants.
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Affiliation(s)
- Thomas Spallek
- RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan;
| | - Charles W Melnyk
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Takanori Wakatake
- RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan
- Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Jing Zhang
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Yuki Sakamoto
- Imaging Frontier Center, Organization for Research Advancement, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Takatoshi Kiba
- RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan
| | - Satoko Yoshida
- Institute for Research Initiatives, Division for Research Strategy, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan
| | - Sachihiro Matsunaga
- Imaging Frontier Center, Organization for Research Advancement, Tokyo University of Science, Noda, Chiba 278-8510, Japan
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | | | - Ken Shirasu
- RIKEN Center for Sustainable Resource Science, Yokohama 230-0045, Japan;
- Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
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54
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Zahajská L, Nisler J, Voller J, Gucký T, Pospíšil T, Spíchal L, Strnad M. Preparation, characterization and biological activity of C8-substituted cytokinins. PHYTOCHEMISTRY 2017; 135:115-127. [PMID: 27986278 DOI: 10.1016/j.phytochem.2016.12.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/21/2016] [Accepted: 12/03/2016] [Indexed: 06/06/2023]
Abstract
Naturally occurring cytokinins are adenine-based plant hormones. Although, the effect of various substituents at positions N1, C2, N3, N6, N7, or N9 on the biological activity of cytokinins has been studied, the C8-substituted compounds have received little attention. Here, we report the synthesis and in vitro biological testing of thirty-one cytokinin derivatives substituted at the C8 position of the adenine skeleton and twenty-seven compounds which served as their N9-tetrahydropyranyl protected precursors. The cytokinin activity of all the compounds was determined in classical cytokinin biotests (wheat leaf senescence, Amaranthus and tobacco callus assays). With some exceptions, the compounds with a N9-tetrahydropyranyl group were generally less active than their de-protected analogs. The latter were further tested for their ability to activate the Arabidopsis cytokinin receptors AHK3 and CRE1/AHK4 in bacterial receptor activation assays. Using this approach, we identified derivatives bearing short aliphatic chains and retaining high cytokinin activity. Such compounds are suitable candidates for fluorescence labeling or as protein-affinity ligands. We further found that some C8-substituted cytokinins exhibited no or lower cytotoxicity toward tobacco cells when compared to their parent compound. Therefore, we also present and discuss the cytotoxicity of all the compounds against three normal human cell lines.
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Affiliation(s)
- Lenka Zahajská
- Isotope Laboratory, Institute of Experimental Botany, AS CR, Vídeňská 1083, 14220 Prague 4, Czechia
| | - Jaroslav Nisler
- Isotope Laboratory, Institute of Experimental Botany, AS CR, Vídeňská 1083, 14220 Prague 4, Czechia; Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia.
| | - Jiří Voller
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia
| | - Tomáš Gucký
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia
| | - Tomáš Pospíšil
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia
| | - Lukáš Spíchal
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia
| | - Miroslav Strnad
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, AS CR & Palacký University, Šlechtitelů 27, Olomouc 783 71, Czechia
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55
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Brütting C, Schäfer M, Vanková R, Gase K, Baldwin IT, Meldau S. Changes in cytokinins are sufficient to alter developmental patterns of defense metabolites in Nicotiana attenuata. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:15-30. [PMID: 27557345 PMCID: PMC5245775 DOI: 10.1111/tpj.13316] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 08/22/2016] [Accepted: 08/23/2016] [Indexed: 05/05/2023]
Abstract
Plant defense metabolites are well known to be regulated developmentally. The optimal defense (OD) theory posits that a tssue's fitness values and probability of attack should determine defense metabolite allocations. Young leaves are expected to provide a larger fitness value to the plant, and therefore their defense allocations should be higher when compared with older leaves. The mechanisms that coordinate development with defense remain unknown and frequently confound tests of the OD theory predictions. Here we demonstrate that cytokinins (CKs) modulate ontogeny-dependent defenses in Nicotiana attenuata. We found that leaf CK levels highly correlate with inducible defense expressions with high levels in young and low levels in older leaves. We genetically manipulated the developmental patterns of two different CK classes by using senescence- and chemically inducible expression of CK biosynthesis genes. Genetically modifying the levels of different CKs in leaves was sufficient to alter ontogenic patterns of defense metabolites. We conclude that the developmental regulation of growth hormones that include CKs plays central roles in connecting development with defense and therefore in establishing optimal patterns of defense allocation in plants.
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Affiliation(s)
- Christoph Brütting
- Max Planck Institute for Chemical Ecology, Department of Molecular Ecology, Hans Knöll Str. 8, Jena 07745, Germany
| | - Martin Schäfer
- Max Planck Institute for Chemical Ecology, Department of Molecular Ecology, Hans Knöll Str. 8, Jena 07745, Germany
| | - Radomira Vanková
- Institute of Experimental Botany AS CR, Laboratory of Hormonal Regulations in Plants, Rozvojová 263, 165 02 Prague 6 - Lysolaje, Czech Republic
| | - Klaus Gase
- Max Planck Institute for Chemical Ecology, Department of Molecular Ecology, Hans Knöll Str. 8, Jena 07745, Germany
| | - Ian T. Baldwin
- Max Planck Institute for Chemical Ecology, Department of Molecular Ecology, Hans Knöll Str. 8, Jena 07745, Germany
| | - Stefan Meldau
- Max Planck Institute for Chemical Ecology, Department of Molecular Ecology, Hans Knöll Str. 8, Jena 07745, Germany
- German Centre for integrative Biodiversity Research (iDiv), Deutscher Platz 5, Leipzig 04107, Germany
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56
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Wallmeroth N, Anastasia AK, Harter K, Berendzen KW, Mira-Rodado V. Arabidopsis response regulator 22 inhibits cytokinin-regulated gene transcription in vivo. PROTOPLASMA 2017; 254:597-601. [PMID: 26769709 DOI: 10.1007/s00709-016-0944-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 01/06/2016] [Indexed: 05/24/2023]
Abstract
Cytokinin signaling in Arabidopsis is carried out by a two-component system (TCS) multi-step phosphorelay mechanism that involves three different protein families: histidine kinases (AHKs), phosphotransfer proteins (AHPs), and response regulators (ARRs) that are in turn, subdivided into A-, B- and C-type ARRs depending on their function and structure. Upon cytokinin perception, AHK proteins autophosphorylate; this phosphate is then transferred from the AHKs to the AHPs to finally reach the ARRs. When B-type ARRs are activated by phosphorylation, they function as transcription factors that regulate the expression of cytokinin-dependent genes such as the A-type ARRs, among many others. In cytokinin signaling, while A- and B-type ARR function is well understood, it is still unclear if C-type ARRs (ARR22 and ARR24) play a role in this mechanism. Here, we describe a novel method suitable to study TCS activity natively as an in vivo system. We also show that ARR22 inhibits gene transcription of an A-type ARR upon cytokinin treatment in vivo. Consequently, we propose that ARR22, by acting as a phosphatase on specific AHPs, disrupts the TCS phosphorelay and prevents B-type ARR phosphorylation, and thus their activation as transcription factors, explaining the observed deactivation of cytokinin-responsive genes.
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Affiliation(s)
- Niklas Wallmeroth
- Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany
| | - Anna Katharina Anastasia
- Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany
| | - Klaus Harter
- Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany
| | - Kenneth Wayne Berendzen
- Center for Plant Molecular Biology (ZMBP), Central Facilities, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
| | - Virtudes Mira-Rodado
- Center for Plant Molecular Biology (ZMBP), Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.
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57
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Abstract
The history of auxin and cytokinin biology including the initial discoveries by father-son duo Charles Darwin and Francis Darwin (1880), and Gottlieb Haberlandt (1919) is a beautiful demonstration of unceasing continuity of research. Novel findings are integrated into existing hypotheses and models and deepen our understanding of biological principles. At the same time new questions are triggered and hand to hand with this new methodologies are developed to address these new challenges.
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Affiliation(s)
- Andrej Hurný
- Institute of Science and Technology, Am Campus 1, 3400, Klosterneuburg, Austria
| | - Eva Benková
- Institute of Science and Technology, Am Campus 1, 3400, Klosterneuburg, Austria.
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58
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Push-Pull and Feedback Mechanisms Can Align Signaling System Outputs with Inputs. Cell Syst 2016; 3:444-455.e2. [PMID: 27894998 DOI: 10.1016/j.cels.2016.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 06/10/2016] [Accepted: 10/04/2016] [Indexed: 11/23/2022]
Abstract
Many cell signaling systems, including the yeast pheromone response system, exhibit "dose-response alignment" (DoRA), in which output of one or more downstream steps closely matches the fraction of occupied receptors. DoRA can improve the fidelity of transmitted dose information. Here, we searched systematically for biochemical network topologies that produced DoRA. Most networks, including many containing feedback and feedforward loops, could not produce DoRA. However, networks including "push-pull" mechanisms, in which the active form of a signaling species stimulates downstream activity and the nominally inactive form reduces downstream activity, enabled perfect DoRA. Networks containing feedbacks enabled DoRA, but only if they also compared feedback to input and adjusted output to match. Our results establish push-pull as a non-feedback mechanism to align output with variable input and maximize information transfer in signaling systems. They also suggest genetic approaches to determine whether particular signaling systems use feedback or push-pull control.
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Boivin S, Kazmierczak T, Brault M, Wen J, Gamas P, Mysore KS, Frugier F. Different cytokinin histidine kinase receptors regulate nodule initiation as well as later nodule developmental stages in Medicago truncatula. PLANT, CELL & ENVIRONMENT 2016; 39:2198-209. [PMID: 27341695 DOI: 10.1111/pce.12779] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 06/11/2016] [Indexed: 05/08/2023]
Abstract
Legume plants adapt to low nitrogen by developing an endosymbiosis with nitrogen-fixing soil bacteria to form a new specific organ: the nitrogen-fixing nodule. In the Medicago truncatula model legume, the MtCRE1 cytokinin receptor is essential for this symbiotic interaction. As three other putative CHASE-domain containing histidine kinase (CHK) cytokinin receptors exist in M. truncatula, we determined their potential contribution to this symbiotic interaction. The four CHKs have extensive redundant expression patterns at early nodulation stages but diverge in differentiated nodules, even though MtCHK1/MtCRE1 has the strongest expression at all stages. Mutant and knock-down analyses revealed that other CHKs than MtCHK1/CRE1 are positively involved in nodule initiation, which explains the delayed nodulation phenotype of the chk1/cre1 mutant. In addition, cre1 nodules exhibit an increased growth, whereas other chk mutants have no detectable phenotype, and the maintained nitrogen fixation capacity in cre1 requires other CHK genes. Interestingly, an AHK4/CRE1 genomic locus from the aposymbiotic Arabidopsis plant rescues nodule initiation but not the nitrogen fixation capacity. This indicates that different CHK cytokinin signalling pathways regulate not only nodule initiation but also later developmental stages, and that legume-specific determinants encoded by the MtCRE1 gene are required for later nodulation stages than initiation.
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Affiliation(s)
- Stéphane Boivin
- Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France
| | - Théophile Kazmierczak
- Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France
| | - Mathias Brault
- Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France
| | - Jiangqi Wen
- Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, USA
| | - Pascal Gamas
- Laboratoire des Interactions Plantes-Microorganismes (LIPM), Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Kirankumar S Mysore
- Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, USA
| | - Florian Frugier
- Institute of Plant Sciences-Paris Saclay (IPS2), CNRS, INRA, Univ Paris-Sud, Univ Paris-Diderot, Univ d'Evry, Université Paris-Saclay, Bâtiment 630, 91190, Gif-sur-Yvette, France.
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60
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Nisler J, Kopečný D, Končitíková R, Zatloukal M, Bazgier V, Berka K, Zalabák D, Briozzo P, Strnad M, Spíchal L. Novel thidiazuron-derived inhibitors of cytokinin oxidase/dehydrogenase. PLANT MOLECULAR BIOLOGY 2016; 92:235-48. [PMID: 27422623 DOI: 10.1007/s11103-016-0509-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 06/29/2016] [Indexed: 05/11/2023]
Abstract
Two new TDZ derivatives (HETDZ and 3FMTDZ) are very potent inhibitors of CKX and are promising candidates for in vivo studies. Cytokinin hormones regulate a wide range of essential processes in plants. Thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-yl urea, TDZ), formerly registered as a cotton defoliant, is a well known inhibitor of cytokinin oxidase/dehydrogenase (CKX), an enzyme catalyzing the degradation of cytokinins. TDZ thus increases the lifetime of cytokinins and their effects in plants. We used in silico modeling to design, synthesize and characterize twenty new TDZ derivatives with improved inhibitory properties. Two compounds, namely 1-[1,2,3]thiadiazol-5-yl-3-(3-trifluoromethoxy-phenyl)urea (3FMTDZ) and 1-[2-(2-hydroxyethyl)phenyl]-3-(1,2,3-thiadiazol-5-yl)urea (HETDZ), displayed up to 15-fold lower IC 50 values compared with TDZ for AtCKX2 from Arabidopsis thaliana and ZmCKX1 and ZmCKX4a from Zea mays. Binding modes of 3FMTDZ and HETDZ were analyzed by X-ray crystallography. Crystal structure complexes, solved at 2.0 Å resolution, revealed that HETDZ and 3FMTDZ bound differently in the active site of ZmCKX4a: the thiadiazolyl ring of 3FMTDZ was positioned over the isoalloxazine ring of FAD, whereas that of HETDZ had the opposite orientation, pointing toward the entrance of the active site. The compounds were further tested for cytokinin activity in several cytokinin bioassays. We suggest that the combination of simple synthesis, lowered cytokinin activity, and enhanced inhibitory effects on CKX isoforms, makes 3FMTDZ and HETDZ suitable candidates for in vivo studies.
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Affiliation(s)
- Jaroslav Nisler
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research (CRH), Institute of Experimental Botany AS CR, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
- Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
- Department of Chemistry of Natural Compounds, Faculty of Food and Biochemical Technology, University of Chemistry and Technology in Prague, Technická 5, 166 28, Prague, Czech Republic.
| | - David Kopečný
- Department of Protein Biochemistry and Proteomics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
| | - Radka Končitíková
- Department of Protein Biochemistry and Proteomics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
| | - Marek Zatloukal
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research (CRH), Institute of Experimental Botany AS CR, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
- Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
| | - Václav Bazgier
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research (CRH), Institute of Experimental Botany AS CR, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
- Department of Physical Chemistry, Faculty of Science, Palacký University, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic
| | - Karel Berka
- Department of Physical Chemistry, Faculty of Science, Palacký University, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic
| | - David Zalabák
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
| | - Pierre Briozzo
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, Université Paris-Saclay, 78026, Versailles, France
| | - Miroslav Strnad
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research (CRH), Institute of Experimental Botany AS CR, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
| | - Lukáš Spíchal
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research (CRH), Institute of Experimental Botany AS CR, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
- Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic
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Šmehilová M, Dobrůšková J, Novák O, Takáč T, Galuszka P. Cytokinin-Specific Glycosyltransferases Possess Different Roles in Cytokinin Homeostasis Maintenance. FRONTIERS IN PLANT SCIENCE 2016; 7:1264. [PMID: 27602043 PMCID: PMC4993776 DOI: 10.3389/fpls.2016.01264] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 08/08/2016] [Indexed: 05/18/2023]
Abstract
Plant hormones cytokinins (CKs) are one of the major mediators of physiological responses throughout plant life span. Therefore, a proper homeostasis is maintained by regulation of their active levels. Besides degradation, CKs are deactivated by uridine diphosphate glycosyltransferases (UGTs). Physiologically, CKs active levels decline in senescing organs, providing a signal to nutrients that a shift to reproductive tissues has begun. In this work, we show CK glucosides distribution in Arabidopsis leaves during major developmental transition phases. Besides continuous accumulation of N-glucosides we detected sharp maximum of the glucosides in senescence. This is caused prevalently by N7-glucosides followed by N9-glucosides and specifically also by trans-zeatin-O-glucoside (tZOG). Interestingly, we observed a similar trend in response to exogenously applied CK. In Arabidopsis, only three UGTs deactivate CKs in vivo: UGT76C1, UGT76C2 and UGT85A1. We thereby show that UGT85A1 is specifically expressed in senescent leaves whereas UGT76C2 is activated rapidly in response to exogenously applied CK. To shed more light on the UGTs physiological roles, we performed a comparative study on UGTs loss-of-function mutants, characterizing a true ugt85a1-1 loss-of-function mutant for the first time. Although no altered phenotype was detected under standard condition we observed reduced chlorophyll degradation with increased anthocyanin accumulation in our experiment on detached leaves accompanied by senescence and stress related genes modulated expression. Among the mutants, ugt76c2 possessed extremely diminished CK N-glucosides levels whereas ugt76c1 showed some specificity toward cis-zeatin (cZ). Besides tZOG, a broader range of CK glucosides was decreased in ugt85a1-1. Performing CK metabolism gene expression profiling, we revealed that activation of CK degradation pathway serves as a general regulatory mechanism of disturbed CK homeostasis followed by decreased CK signaling in all UGT mutants. In contrast, a specific regulation of CKX7, CKX1 and CKX2 was observed for each individual UGT mutant isoform after exogenous CK uptake. Employing an in silico prediction we proposed cytosolic localization of UGT76C1 and UGT76C2, that we further confirmed by GFP tagging of UGT76C2. Integrating all the results, we therefore hypothesize that UGTs possess different physiological roles in Arabidopsis and serve as a fine-tuning mechanism of active CK levels in cytosol.
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Affiliation(s)
- Mária Šmehilová
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in OlomoucOlomouc, Czech Republic
| | - Jana Dobrůšková
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in OlomoucOlomouc, Czech Republic
| | - Ondřej Novák
- Laboratory of Growth Regulators and Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc and Institute of Experimental Botany ASCROlomouc, Czech Republic
| | - Tomáš Takáč
- Department of Cell Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in OlomoucOlomouc, Czech Republic
| | - Petr Galuszka
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in OlomoucOlomouc, Czech Republic
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62
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Ohse B, Hammerbacher A, Seele C, Meldau S, Reichelt M, Ortmann S, Wirth C. Salivary cues: simulated roe deer browsing induces systemic changes in phytohormones and defence chemistry in wild‐grown maple and beech saplings. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12717] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bettina Ohse
- Department of Systematic Botany and Functional Biodiversity Institute of Biology University of Leipzig Johannisallee 21, 04103 Leipzig Germany
| | - Almuth Hammerbacher
- Department of Biochemistry Max Planck Institute for Chemical Ecology Hans‐Knoell‐Strasse 8, 07745 Jena Germany
| | - Carolin Seele
- Department of Systematic Botany and Functional Biodiversity Institute of Biology University of Leipzig Johannisallee 21, 04103 Leipzig Germany
| | - Stefan Meldau
- Department of Molecular Ecology Max Planck Institute for Chemical Ecology Hans‐Knoell‐Strasse 8, 07745 Jena Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig Deutscher Platz 5e, 04103 Leipzig Germany
| | - Michael Reichelt
- Department of Biochemistry Max Planck Institute for Chemical Ecology Hans‐Knoell‐Strasse 8, 07745 Jena Germany
| | - Sylvia Ortmann
- Department of Evolutionary Ecology Leibniz Institute for Zoo and Wildlife Research (IZW) Alfred‐Kowalke‐Straβe 17, 10315 Berlin Germany
| | - Christian Wirth
- Department of Systematic Botany and Functional Biodiversity Institute of Biology University of Leipzig Johannisallee 21, 04103 Leipzig Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig Deutscher Platz 5e, 04103 Leipzig Germany
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63
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Hinsch J, Galuszka P, Tudzynski P. Functional characterization of the first filamentous fungal tRNA-isopentenyltransferase and its role in the virulence of Claviceps purpurea. THE NEW PHYTOLOGIST 2016; 211:980-992. [PMID: 27074411 DOI: 10.1111/nph.13960] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 03/01/2016] [Indexed: 06/05/2023]
Abstract
In plants, cytokinins (CKs) are synthesized de novo or by the degradation of modified tRNAs. Recently, the first fungal de novo pathway was identified within the plant pathogen Claviceps purpurea. As the deletion of the de novo pathway did not lead to a complete loss of CKs, this work focuses on the tRNA-modifying protein tRNA-isopentenyltransferase (CptRNA-IPT). The contribution of this enzyme to the CK pool of Claviceps and the role of CKs in the host-pathogen interaction are emphasized. The effects of the deletion of cptRNA-ipt and the double deletion of cptRNA-ipt and the key gene of de novo biosynthesis cpipt-log on growth, CK biosynthesis and virulence were analyzed. In addition, the sites of action of CptRNA-IPT were visualized using reporter gene fusions. In addition to CK-independent functions, CptRNA-IPT was essential for the biosynthesis of cis-zeatin (cZ) and contributed to the formation of isopentenyladenine (iP) and trans-zeatin (tZ). Although ΔcptRNA-ipt was reduced in virulence, the 'CK-free' double deletion mutant was nearly apathogenic. The results prove a redundancy of the CK biosynthesis pathway in C. purpurea for iP and tZ formation. Moreover, we show, for the first time, that CKs are required for the successful establishment of a host-fungus interaction.
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Affiliation(s)
- Janine Hinsch
- Institute of Plant Biology and Biotechnology, Westfälische Wilhelms-University Münster, Schlossplatz 8, 48143, Münster, Germany
| | - Petr Galuszka
- Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Paul Tudzynski
- Institute of Plant Biology and Biotechnology, Westfälische Wilhelms-University Münster, Schlossplatz 8, 48143, Münster, Germany
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Synthesis of a Cytokinin Linked by a Spacer to Dexamethasone and Biotin: Conjugates to Detect Cytokinin-Binding Proteins. Molecules 2016; 21:molecules21050576. [PMID: 27144549 PMCID: PMC6273812 DOI: 10.3390/molecules21050576] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 04/25/2016] [Accepted: 04/25/2016] [Indexed: 12/13/2022] Open
Abstract
Yeast cells expressing cDNA libraries have provided two new approaches to facilitate further identification of cytokinin-binding proteins and receptors. These are the yeast three hybrid (Y3H) system and fluorescence activated cell sorting (FACS). The Y3H system requires a synthetic hybrid ligand comprising an “anchor” moiety (e.g., dexamethasone) linked to a cytokinin via a spacer. In the yeast nucleus, this ligand by binding connects two fusion proteins leading to a reporter gene activation and detection and characterisation of cytokinin binding proteins. Herein is reported the first synthesis of dexamethasone-cytokinin ligands with a spacer linkage. This was attached to the purine ring of 6-benzylaminopurine (BAP) at positions 2, 8 or 9. To achieve this, dexamethasone was modified by periodate oxidation yielding a carboxylic group used for conjugation to the spacer by amide formation. Biotinyl derivatives of cytokinins for FACS included those synthesised by reaction of an activated ester of biotin with 8-(10-amino-decylamino) derivatives of BAP and BAP 9-riboside. Properties of the conjugates and some biological situations where they could be applicable are discussed briefly.
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von Schwartzenberg K, Lindner AC, Gruhn N, Šimura J, Novák O, Strnad M, Gonneau M, Nogué F, Heyl A. CHASE domain-containing receptors play an essential role in the cytokinin response of the moss Physcomitrella patens. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:667-79. [PMID: 26596764 PMCID: PMC4737067 DOI: 10.1093/jxb/erv479] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
While the molecular basis for cytokinin action is quite well understood in flowering plants, little is known about the cytokinin signal transduction in early diverging land plants. The genome of the bryophyte Physcomitrella patens (Hedw.) B.S. encodes three classical cytokinin receptors, the CHASE domain-containing histidine kinases, CHK1, CHK2, and CHK3. In a complementation assay with protoplasts of receptor-deficient Arabidopsis thaliana as well as in cytokinin binding assays, we found evidence that CHK1 and CHK2 receptors can function in cytokinin perception. Using gene targeting, we generated a collection of CHK knockout mutants comprising single (Δchk1, Δchk2, Δchk3), double (Δchk1,2, Δchk1,3, Δchk2,3), and triple (Δchk1,2,3) mutants. Mutants were characterized for their cytokinin response and differentiation capacities. While the wild type did not grow on high doses of cytokinin (1 µM benzyladenine), the Δchk1,2,3 mutant exhibited normal protonema growth. Bud induction assays showed that all three cytokinin receptors contribute to the triggering of budding, albeit to different extents. Furthermore, while the triple mutant showed no response in this bioassay, the remaining mutants displayed budding responses in a diverse manner to different types and concentrations of cytokinins. Determination of cytokinin levels in mutants showed no drastic changes for any of the cytokinins; thus, in contrast to Arabidopsis, revealing only small impacts of cytokinin signaling on homeostasis. In summary, our study provides a first insight into the molecular action of cytokinin in an early diverging land plant and demonstrates that CHK receptors play an essential role in bud induction and gametophore development.
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Affiliation(s)
| | - Ann-Cathrin Lindner
- Biozentrum Klein Flottbek, Universität Hamburg, Ohnhorststr. 18, D-22609 Hamburg, Germany
| | - Njuscha Gruhn
- Institute for Biology/ Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany
| | - Jan Šimura
- Laboratory of Growth Regulators & Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University & Institute of Experimental Botany ASCR, Šlechtitelů 27, CZ-783 71 Olomouc, Czech Republic
| | - Ondřej Novák
- Laboratory of Growth Regulators & Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University & Institute of Experimental Botany ASCR, Šlechtitelů 27, CZ-783 71 Olomouc, Czech Republic
| | - Miroslav Strnad
- Laboratory of Growth Regulators & Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University & Institute of Experimental Botany ASCR, Šlechtitelů 27, CZ-783 71 Olomouc, Czech Republic
| | - Martine Gonneau
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Route de St-Cyr, 78026 Versailles Cedex, France
| | - Fabien Nogué
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Route de St-Cyr, 78026 Versailles Cedex, France
| | - Alexander Heyl
- Institute for Biology/ Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany Biology Department, Adelphi University, Science 116, 1 South Avenue, PO Box 701, Garden City, NY 11530-070, USA
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66
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Pekárová B, Szmitkowska A, Dopitová R, Degtjarik O, Žídek L, Hejátko J. Structural Aspects of Multistep Phosphorelay-Mediated Signaling in Plants. MOLECULAR PLANT 2016; 9:71-85. [PMID: 26633861 DOI: 10.1016/j.molp.2015.11.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 05/16/2023]
Abstract
The multistep phosphorelay (MSP) is a central signaling pathway in plants integrating a wide spectrum of hormonal and environmental inputs and controlling numerous developmental adaptations. For the thorough comprehension of the molecular mechanisms underlying the MSP-mediated signal recognition and transduction, the detailed structural characterization of individual members of the pathway is critical. In this review we describe and discuss the recently known crystal and nuclear magnetic resonance structures of proteins acting in MSP signaling in higher plants, focusing particularly on cytokinin and ethylene signaling in Arabidopsis thaliana. We discuss the range of functional aspects of available structural information including determination of ligand specificity, activation of the receptor via its autophosphorylation, and downstream signal transduction through the phosphorelay. We compare the plant structures with their bacterial counterparts and show that although the overall similarity is high, the differences in structural details are frequent and functionally important. Finally, we discuss emerging knowledge on molecular recognition mechanisms in the MSP, and mention the latest findings regarding structural determinants of signaling specificity in the Arabidopsis MSP that could serve as a general model of this pathway in all higher plants.
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Affiliation(s)
- Blanka Pekárová
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Agnieszka Szmitkowska
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Radka Dopitová
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Oksana Degtjarik
- Faculty of Science, Institute of Chemistry and Biochemistry, University of South Bohemia, 370 05 České Budějovice, Czech Republic
| | - Lukáš Žídek
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Jan Hejátko
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
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67
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Abstract
Cytokinins comprise a family of signaling molecules essential for regulating the growth and development of plants, acting both locally and at a distance. Although much is known about their biosynthesis and transport, important open questions remain.
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Affiliation(s)
- Asami Osugi
- RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Hitoshi Sakakibara
- RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama, 230-0045, Japan. .,Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, 464-8601, Japan.
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68
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A parasitic nematode releases cytokinin that controls cell division and orchestrates feeding site formation in host plants. Proc Natl Acad Sci U S A 2015; 112:12669-74. [PMID: 26417108 DOI: 10.1073/pnas.1503657112] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sedentary plant-parasitic cyst nematodes are biotrophs that cause significant losses in agriculture. Parasitism is based on modifications of host root cells that lead to the formation of a hypermetabolic feeding site (a syncytium) from which nematodes withdraw nutrients. The host cell cycle is activated in an initial cell selected by the nematode for feeding, followed by activation of neighboring cells and subsequent expansion of feeding site through fusion of hundreds of cells. It is generally assumed that nematodes manipulate production and signaling of the plant hormone cytokinin to activate cell division. In fact, nematodes have been shown to produce cytokinin in vitro; however, whether the hormone is secreted into host plants and plays a role in parasitism remained unknown. Here, we analyzed the spatiotemporal activation of cytokinin signaling during interaction between the cyst nematode, Heterodera schachtii, and Arabidopsis using cytokinin-responsive promoter:reporter lines. Our results showed that cytokinin signaling is activated not only in the syncytium but also in neighboring cells to be incorporated into syncytium. An analysis of nematode infection on mutants that are deficient in cytokinin or cytokinin signaling revealed a significant decrease in susceptibility of these plants to nematodes. Further, we identified a cytokinin-synthesizing isopentenyltransferase gene in H. schachtii and show that silencing of this gene in nematodes leads to a significant decrease in virulence due to a reduced expansion of feeding sites. Our findings demonstrate the ability of a plant-parasitic nematode to synthesize a functional plant hormone to manipulate the host system and establish a long-term parasitic interaction.
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69
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Böttcher C, Burbidge CA, Boss PK, Davies C. Changes in transcription of cytokinin metabolism and signalling genes in grape (Vitis vinifera L.) berries are associated with the ripening-related increase in isopentenyladenine. BMC PLANT BIOLOGY 2015; 15:223. [PMID: 26377914 PMCID: PMC4573921 DOI: 10.1186/s12870-015-0611-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/10/2015] [Indexed: 05/02/2023]
Abstract
BACKGROUND Cytokinins are known to play an important role in fruit set and early fruit growth, but their involvement in later stages of fruit development is less well understood. Recent reports of greatly increased cytokinin concentrations in the flesh of ripening kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson) and grapes (Vitis vinifera L.) have suggested that these hormones are implicated in the control of ripening-related processes. RESULTS A similar pattern of isopentenyladenine (iP) accumulation was observed in the ripening fruit of several grapevine cultivars, strawberry (Fragaria ananassa Duch.) and tomato (Solanum lycopersicum Mill.), suggesting a common, ripening-related role for this cytokinin. Significant differences in maximal iP concentrations between grapevine cultivars and between fruit species might reflect varying degrees of relevance or functional adaptations of this hormone in the ripening process. Grapevine orthologues of five Arabidopsis (Arabidopsis thaliana L.) gene families involved in cytokinin metabolism and signalling were identified and analysed for their expression in developing grape berries and a range of other grapevine tissues. Members of each gene family were characterised by distinct expression profiles during berry development and in different grapevine organs, suggesting a complex regulation of cellular cytokinin activities throughout the plant. The post-veraison-specific expression of a set of biosynthesis, activation, perception and signalling genes together with a lack of expression of degradation-related genes during the ripening phase were indicative of a local control of berry iP concentrations leading to the observed accumulation of iP in ripening grapes. CONCLUSIONS The transcriptional analysis of grapevine genes involved in cytokinin production, degradation and response has provided a possible explanation for the ripening-associated accumulation of iP in grapes and other fruit. The pre- and post-veraison-specific expression of different members from each of five gene families suggests a highly complex and finely-tuned regulation of cytokinin concentrations and response to different cytokinin species at particular stages of fruit development. The same complexity and specialisation is also reflected in the distinct expression profiles of cytokinin-related genes in other grapevine organs.
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Affiliation(s)
- Christine Böttcher
- CSIRO Agriculture Flagship, Waite Campus, WIC West Building, PMB2, Glen Osmond, South Australia, 5064, Australia.
| | - Crista A Burbidge
- CSIRO Agriculture Flagship, Waite Campus, WIC West Building, PMB2, Glen Osmond, South Australia, 5064, Australia.
| | - Paul K Boss
- CSIRO Agriculture Flagship, Waite Campus, WIC West Building, PMB2, Glen Osmond, South Australia, 5064, Australia.
| | - Christopher Davies
- CSIRO Agriculture Flagship, Waite Campus, WIC West Building, PMB2, Glen Osmond, South Australia, 5064, Australia.
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70
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Schäfer M, Brütting C, Canales IM, Großkinsky DK, Vankova R, Baldwin IT, Meldau S. The role of cis-zeatin-type cytokinins in plant growth regulation and mediating responses to environmental interactions. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4873-84. [PMID: 25998904 PMCID: PMC5147713 DOI: 10.1093/jxb/erv214] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Cytokinins (CKs) are well-established as important phytohormonal regulators of plant growth and development. An increasing number of studies have also revealed the function of these hormones in plant responses to biotic and abiotic stresses. While the function of certain CK classes, including trans-zeatin and isopentenyladenine-type CKs, have been studied in detail, the role of cis-zeatin-type CKs (cZs) in plant development and in mediating environmental interactions is less well defined. Here we provide a comprehensive summary of the current knowledge about abundance, metabolism and activities of cZs in plants. We outline the history of their analysis and the metabolic routes comprising cZ biosynthesis and degradation. Further we provide an overview of changes in the pools of cZs during plant development and environmental interactions. We summarize studies that investigate the role of cZs in regulating plant development and defence responses to pathogen and herbivore attack and highlight their potential role as 'novel' stress-response markers. Since the functional roles of cZs remain largely based on correlative data and genetic manipulations of their biosynthesis, inactivation and degradation are few, we suggest experimental approaches using transgenic plants altered in cZ levels to further uncover their roles in plant growth and environmental interactions and their potential for crop improvement.
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Affiliation(s)
- Martin Schäfer
- Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Hans-Knöll-Str.8, 07745 Jena, Germany
| | - Christoph Brütting
- Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Hans-Knöll-Str.8, 07745 Jena, Germany
| | - Ivan Meza Canales
- Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Hans-Knöll-Str.8, 07745 Jena, Germany
| | - Dominik K. Großkinsky
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Centre, University of Copenhagen, Højbakkegård Allé 13, 2630 Taastrup, Denmark
| | - Radomira Vankova
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany AS CR, v. v. i., Rozvojová 263, 165 02 Prague 6, Czech Republic
| | - Ian T. Baldwin
- Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Hans-Knöll-Str.8, 07745 Jena, Germany
| | - Stefan Meldau
- KWS SAAT AG, Molecular Physiology (RD-ME-MP), Grimsehlstrasse 31, 37555 Einbeck, Germany, Phone: +49 (0) 5561-311-1391, Fax: +49 (0) 5561-311-1090
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71
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Schäfer M, Meza-Canales ID, Brütting C, Baldwin IT, Meldau S. Cytokinin concentrations and CHASE-DOMAIN CONTAINING HIS KINASE 2 (NaCHK2)- and NaCHK3-mediated perception modulate herbivory-induced defense signaling and defenses in Nicotiana attenuata. THE NEW PHYTOLOGIST 2015; 207:645-58. [PMID: 25919325 DOI: 10.1111/nph.13404] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 03/11/2015] [Indexed: 05/23/2023]
Abstract
Herbivore attack elicits changes in cytokinins (CKs), but how these changes influence defense signaling remains poorly described. We investigated the influence of the CK pathway on the well-described inducible defense pathways of Nicotiana attenuata in response to wounding with and without elicitors from the specialist herbivore Manduca sexta. CK pathway manipulation often suffers from substantial side effects on plant growth and development. We therefore used multiple manipulation tools including spray application of CKs, chemically-inducible expression of the CK biosynthesis enzyme isopentenyltransferase, and transient and constitutive RNAi-mediated gene silencing of CK receptors to resolve the function of CKs in plant defense. The results demonstrated that CK concentrations in leaves and perception through CHASE-DOMAIN CONTAINING HIS KINASE 2 (NaCHK2) and NaCHK3 were important for the accumulation of jasmonic acid (JA) and phenolamides and proteinase inhibitor activity. By contrast, the CK pathway did not promote the accumulation of the active JA-isoleucine conjugate and negatively regulated the release of specific green leaf volatile esters. Interestingly, CK signaling also promotes the systemic phenolamide accumulation. We conclude that the CK pathway is an important regulator of herbivory-inducible defense signaling and chemistry, which expands its reported participation in adjusting a plant's physiology to abiotic and biotic stress responses.
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Affiliation(s)
- Martin Schäfer
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, Jena, 07745, Germany
| | - Ivan D Meza-Canales
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, Jena, 07745, Germany
| | - Christoph Brütting
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, Jena, 07745, Germany
| | - Ian T Baldwin
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, Jena, 07745, Germany
| | - Stefan Meldau
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans Knöll Str. 8, Jena, 07745, Germany
- German Centre for integrative Biodiversity Research (iDiv), Deutscher Platz 5, Leipzig, 04107, Germany
- KWS SAAT AG, Grimsehlstraße 31, Einbeck, 37574, Germany
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van Zeijl A, Op den Camp RHM, Deinum EE, Charnikhova T, Franssen H, Op den Camp HJM, Bouwmeester H, Kohlen W, Bisseling T, Geurts R. Rhizobium Lipo-chitooligosaccharide Signaling Triggers Accumulation of Cytokinins in Medicago truncatula Roots. MOLECULAR PLANT 2015; 8:1213-26. [PMID: 25804975 DOI: 10.1016/j.molp.2015.03.010] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 03/12/2015] [Accepted: 03/15/2015] [Indexed: 05/20/2023]
Abstract
Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides (LCOs). Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizobium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and isopentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase (CCaMK), a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.
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Affiliation(s)
- Arjan van Zeijl
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Rik H M Op den Camp
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Eva E Deinum
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; Department of Systems Biophysics, FOM institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Tatsiana Charnikhova
- Department of Plant Sciences, Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Henk Franssen
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Huub J M Op den Camp
- Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Harro Bouwmeester
- Department of Plant Sciences, Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Wouter Kohlen
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Ton Bisseling
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; College of Science, King Saud University, Post Office Box 2455, Riyadh 11451, Saudi Arabia
| | - René Geurts
- Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
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73
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Kumar MN, Verslues PE. Stress physiology functions of the Arabidopsis histidine kinase cytokinin receptors. PHYSIOLOGIA PLANTARUM 2015; 154:369-80. [PMID: 25263537 DOI: 10.1111/ppl.12290] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 08/13/2014] [Accepted: 09/05/2014] [Indexed: 05/07/2023]
Abstract
Cytokinin signaling has complex effects on abiotic stress responses that remain to be fully elucidated. The Arabidopsis histidine kinases (AHKs), AHK2, AHK3 and CRE1 (cytokinin response1/AHK4) are the principle cytokinin receptors of Arabidopsis. Using a set of ahk mutants, we found dramatic differences in response to low water potential and salt stress among the AHKs. ahk3-3 mutants had increased root elongation after transfer to low water potential media. Conversely ahk2-2 was hypersensitive to salt stress in terms of root growth and fresh weight and accumulated higher than wild-type levels of proline specifically under salt stress. Strongly reduced proline accumulation in ahk double mutants after low water potential treatment indicated a more general role of cytokinin signaling in proline metabolism. Reduced P5CS1 (Δ(1) -pyrroline-5-carboxylate synthetase1) gene expression may have contributed to this reduced proline accumulation. Low water potential phenotypes of ahk mutants were not caused by altered abscisic acid (ABA) accumulation as all ahk mutants had wild-type ABA levels, despite the observation that ahk double mutants had reduced NCED3 (9-cis-epoxycartenoid dioxygenase3) expression when exposed to low water potential. No difference in osmoregulatory solute accumulation was detected in any of the ahk mutants indicating that they do not affect drought responsive osmotic adjustment. Overall, our examination of ahk mutants found specific phenotypes associated with AHK2 and AHK3 as well as a general function of cytokinin signaling in proline accumulation and low water potential induction of P5CS1 and NCED3 expression. These results show the stress physiology function of AHKs at a new level of detail.
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Affiliation(s)
- M Nagaraj Kumar
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 115, Taiwan
| | - Paul E Verslues
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 115, Taiwan
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74
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Lomin SN, Krivosheev DM, Steklov MY, Arkhipov DV, Osolodkin DI, Schmülling T, Romanov GA. Plant membrane assays with cytokinin receptors underpin the unique role of free cytokinin bases as biologically active ligands. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1851-63. [PMID: 25609827 PMCID: PMC4378623 DOI: 10.1093/jxb/eru522] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 12/05/2014] [Accepted: 12/19/2014] [Indexed: 05/18/2023]
Abstract
Cytokinin receptors play a key role in cytokinin-dependent processes regulating plant growth, development, and adaptation; therefore, the functional properties of these receptors are of great importance. Previously the properties of cytokinin receptors were investigated in heterologous assay systems using unicellular microorganisms, mainly bacteria, expressing receptor proteins. However, within microorganisms receptors reside in an alien environment that might distort the receptor properties. Therefore, a new assay system has been developed allowing studies of individual receptors within plant membranes (i.e. closer to their natural environment). The main ligand-binding characteristics of receptors from Arabidopsis [AHK2, AHK3, and AHK4] and maize (ZmHK1) were refined in this new system, and the properties of full-length Arabidopsis receptor AHK2 were characterized for the first time. Ligand specificity profiles of receptors towards cytokinin bases were comparable with the profiles retrieved in bacterial assay systems. In contrast, cytokinin-9-ribosides displayed a strongly reduced affinity for receptors in the plant assay system, indicating that ribosides as the common transport form of cytokinins have no or very weak cytokinin activity. This underpins the central role of free bases as the sole biologically active cytokinin compounds. According to molecular modelling and docking studies, N (9)-ribosylation alters the bonding pattern in cytokinin-receptor interaction and prevents β6-β7 loop movement important for tight hormone binding. A common feature of all receptors was a greatly reduced ligand binding at low (5.0-5.5) pH. The particularly high sensitivity of ZmHK1 to pH changes leads to the suggestion that some cytokinin receptors may play an additional role as pH sensors in the lumen of the endoplasmic reticulum.
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Affiliation(s)
- Sergey N Lomin
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia
| | - Dmitry M Krivosheev
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia
| | - Mikhail Yu Steklov
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia
| | - Dmitry V Arkhipov
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia
| | - Dmitry I Osolodkin
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russia
| | - Thomas Schmülling
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany
| | - Georgy A Romanov
- Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1, 119992 Moscow, Russia
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75
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Hamann T. The plant cell wall integrity maintenance mechanism-concepts for organization and mode of action. PLANT & CELL PHYSIOLOGY 2015; 56:215-23. [PMID: 25416836 DOI: 10.1093/pcp/pcu164] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
One of the main differences between plant and animal cells are the walls surrounding plant cells providing structural support during development and protection like an adaptive armor against biotic and abiotic stress. During recent years it has become widely accepted that plant cells use a dedicated system to monitor and maintain the functional integrity of their walls. Maintenance of integrity is achieved by modifying the cell wall and cellular metabolism in order to permit tightly controlled changes in wall composition and structure. While a substantial amount of evidence supporting the existence of the mechanism has been reported, knowledge regarding its precise mode of action is still limited. The currently available evidence suggests similarities of the plant mechanism with respect to both design principles and molecular components involved to the very well characterized system active in the model organism Saccharomyces cerevisiae. There the system has been implicated in cell morphogenesis as well as response to abiotic stresses such as osmotic challenges. Here the currently available knowledge on the yeast system will be reviewed initially to provide a framework for the subsequent discussion of the plant cell wall integrity maintenance mechanism. The review will then end with a discussion on possible design principles for the cell wall integrity maintenance mechanism and the function of the plant turgor pressure in this context.
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Affiliation(s)
- Thorsten Hamann
- Department of Biology, Høgskoleringen 5, Realfagbygget, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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76
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Schäfer M, Meza-Canales ID, Navarro-Quezada A, Brütting C, Vanková R, Baldwin IT, Meldau S. Cytokinin levels and signaling respond to wounding and the perception of herbivore elicitors in Nicotiana attenuata. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:198-212. [PMID: 24924599 PMCID: PMC4286249 DOI: 10.1111/jipb.12227] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 06/11/2014] [Indexed: 05/21/2023]
Abstract
Nearly half a century ago insect herbivores were found to induce the formation of green islands by manipulating cytokinin (CK) levels. However, the response of the CK pathway to attack by chewing insect herbivores remains unclear. Here, we characterize the CK pathway of Nicotiana attenuata (Torr. ex S. Wats.) and its response to wounding and perception of herbivore-associated molecular patterns (HAMPs). We identified 44 genes involved in CK biosynthesis, inactivation, degradation, and signaling. Leaf wounding rapidly induced transcriptional changes in multiple genes throughout the pathway, as well as in the levels of CKs, including isopentenyladenosine and cis-zeatin riboside; perception of HAMPs present in the oral secretions (OS) of the specialist herbivore Manduca sexta amplified these responses. The jasmonate pathway, which triggers many herbivore-induced processes, was not required for these HAMP-triggered changes, but rather suppressed the CK responses. Interestingly CK pathway changes were observed also in systemic leaves in response to wounding and OS application indicating a role of CKs in mediating long distance systemic processes in response to herbivory. Since wounding and grasshopper OS elicited similar accumulations of CKs in Arabidopsis thaliana L., we propose that CKs are integral components of wounding and HAMP-triggered responses in many plant species.
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Affiliation(s)
- Martin Schäfer
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
| | - Ivan D Meza-Canales
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
| | - Aura Navarro-Quezada
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
| | - Christoph Brütting
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
| | - Radomira Vanková
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany AS CR165 02 Prague 6-Lysolaje, Czech Republic
| | - Ian T Baldwin
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
| | - Stefan Meldau
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology07745, Jena, Germany
- German Centre for integrative Biodiversity Research (iDiv)04107, Leipzig, Germany
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77
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Kuderová A, Gallová L, Kuricová K, Nejedlá E, Čurdová A, Micenková L, Plíhal O, Šmajs D, Spíchal L, Hejátko J. Identification of AHK2- and AHK3-like cytokinin receptors in Brassica napus reveals two subfamilies of AHK2 orthologues. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:339-53. [PMID: 25336686 DOI: 10.1093/jxb/eru422] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Cytokinin (CK) signalling is known to play key roles in the regulation of plant growth and development, crop yields, and tolerance to both abiotic stress and pathogen defences, but the mechanisms involved are poorly characterized in dicotyledonous crops. Here the identification and functional characterization of sensor histidine kinases homologous to Arabidopsis CK receptors AHK2 and AHK3 in winter oilseed rape are presented. Five CHASE-containing His kinases were identified in Brassica napus var. Tapidor (BnCHK1-BnCHK5) by heterologous hybridization of its genomic library with gene-specific probes from Arabidopsis. The identified bacterial artificial chromosome (BAC) clones were fingerprinted and representative clones in five distinct groups were sequenced. Using a bioinformatic approach and cDNA cloning, the precise gene and putative protein domain structures were determined. Based on phylogenetic analysis, four AHK2 (BnCHK1-BnCHK4) homologues and one AHK3 (BnCHK5) homologue were defined. It is further suggested that BnCHK1 and BnCHK3, and BnCHK5 are orthologues of AHK2 and AHK3, originally from the B. rapa A genome, respectively. BnCHK1, BnCHK3, and BnCHK5 displayed high affinity for trans-zeatin (1-3nM) in a live-cell competitive receptor assay, but not with other plant hormones (indole acetic acid, GA3, and abscisic acid), confirming the prediction that they are genuine CK receptors. It is shown that BnCHK1 and BnCHK3, and BnCHK5 display distinct preferences for various CK bases and metabolites, characteristic of their AHK counterparts, AHK2 and AHK3, respectively. Interestingly, the AHK2 homologues could be divided into two subfamilies (BnCHK1/BnCK2 and BnCHK3/BnCHK4) that differ in putative transmembrane domain topology and CK binding specificity, thus implying potential functional divergence.
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Affiliation(s)
- Alena Kuderová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Lucia Gallová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, 783 71 Olomouc, Czech Republic
| | - Katarína Kuricová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Eliška Nejedlá
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Anna Čurdová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Lenka Micenková
- Faculty of Medicine, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Ondřej Plíhal
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, 783 71 Olomouc, Czech Republic
| | - David Šmajs
- Faculty of Medicine, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Lukáš Spíchal
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, 783 71 Olomouc, Czech Republic
| | - Jan Hejátko
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
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78
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Erickson JL, Ziegler J, Guevara D, Abel S, Klösgen RB, Mathur J, Rothstein SJ, Schattat MH. Agrobacterium-derived cytokinin influences plastid morphology and starch accumulation in Nicotiana benthamiana during transient assays. BMC PLANT BIOLOGY 2014; 14:127. [PMID: 24886417 PMCID: PMC4062310 DOI: 10.1186/1471-2229-14-127] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 04/24/2014] [Indexed: 05/06/2023]
Abstract
BACKGROUND Agrobacterium tumefaciens-based transient assays have become a common tool for answering questions related to protein localization and gene expression in a cellular context. The use of these assays assumes that the transiently transformed cells are observed under relatively authentic physiological conditions and maintain 'normal' sub-cellular behaviour. Although this premise is widely accepted, the question of whether cellular organization and organelle morphology is altered in Agrobacterium-infiltrated cells has not been examined in detail. The first indications of an altered sub-cellular environment came from our observation that a common laboratory strain, GV3101(pMP90), caused a drastic increase in stromule frequency. Stromules, or 'stroma-filled-tubules' emanate from the surface of plastids and are sensitive to a variety of biotic and abiotic stresses. Starting from this observation, the goal of our experiments was to further characterize the changes to the cell resulting from short-term bacterial infestation, and to identify the factor responsible for eliciting these changes. RESULTS Using a protocol typical of transient assays we evaluated the impact of GV3101(pMP90) infiltration on chloroplast behaviour and morphology in Nicotiana benthamiana. Our experiments confirmed that GV3101(pMP90) consistently induces stromules and alters plastid position relative to the nucleus. These effects were found to be the result of strain-dependant secretion of cytokinin and its accumulation in the plant tissue. Bacterial production of the hormone was found to be dependant on the presence of a trans-zeatin synthase gene (tzs) located on the Ti plasmid of GV3101(pMP90). Bacteria-derived cytokinins were also correlated with changes to both soluble sugar level and starch accumulation. CONCLUSION Although we have chosen to focus on how transient Agrobacterium infestation alters plastid based parameters, these changes to the morphology and position of a single organelle, combined with the measured increases in sugar and starch content, suggest global changes to cell physiology. This indicates that cells visualized during transient assays may not be as 'normal' as was previously assumed. Our results suggest that the impact of the bacteria can be minimized by choosing Agrobacterium strains devoid of the tzs gene, but that the alterations to sub-cellular organization and cell carbohydrate status cannot be completely avoided using this strategy.
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Affiliation(s)
- Jessica L Erickson
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
| | - Jörg Ziegler
- Abteilung Molekulare Signalverarbeitung, Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, Halle/Saale 06120, Germany
| | - David Guevara
- Present Address: Pioneer Hi-Bred, 12111 Mississauga Rd, Georgetown, ON L7G 4S7, Canada
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Steffen Abel
- Abteilung Molekulare Signalverarbeitung, Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, Halle/Saale 06120, Germany
| | - Ralf B Klösgen
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
| | - Jaideep Mathur
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Steven J Rothstein
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Martin H Schattat
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
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79
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Cortleven A, Nitschke S, Klaumünzer M, AbdElgawad H, Asard H, Grimm B, Riefler M, Schmülling T. A novel protective function for cytokinin in the light stress response is mediated by the Arabidopsis histidine kinase2 and Arabidopsis histidine kinase3 receptors. PLANT PHYSIOLOGY 2014; 164:1470-83. [PMID: 24424319 PMCID: PMC3938634 DOI: 10.1104/pp.113.224667] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 01/10/2014] [Indexed: 05/17/2023]
Abstract
Cytokinins are plant hormones that regulate diverse processes in plant development and responses to biotic and abiotic stresses. In this study, we show that Arabidopsis (Arabidopsis thaliana) plants with a reduced cytokinin status (i.e. cytokinin receptor mutants and transgenic cytokinin-deficient plants) are more susceptible to light stress compared with wild-type plants. This was reflected by a stronger photoinhibition after 24 h of high light (approximately 1,000 µmol m(-2) s(-1)), as shown by the decline in maximum quantum efficiency of photosystem II photochemistry. Photosystem II, especially the D1 protein, is highly sensitive to the detrimental impact of light. Therefore, photoinhibition is always observed when the rate of photodamage exceeds the rate of D1 repair. We demonstrate that in plants with a reduced cytokinin status, the D1 protein level was strongly decreased upon light stress. Inhibition of the D1 repair cycle by lincomycin treatment indicated that these plants experience stronger photodamage. The efficiency of photoprotective mechanisms, such as nonenzymatic and enzymatic scavenging systems, was decreased in plants with a reduced cytokinin status, which could be a cause for the increased photodamage and subsequent D1 degradation. Additionally, slow and incomplete recovery in these plants after light stress indicated insufficient D1 repair. Mutant analysis revealed that the protective function of cytokinin during light stress depends on the Arabidopsis histidine KINASE2 (AHK2) and AHK3 receptors and the type B Arabidopsis response regulator1 (ARR1) and ARR12. We conclude that proper cytokinin signaling and regulation of specific target genes are necessary to protect leaves efficiently from light stress.
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80
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Kiba T, Takei K, Kojima M, Sakakibara H. Side-chain modification of cytokinins controls shoot growth in Arabidopsis. Dev Cell 2014; 27:452-61. [PMID: 24286826 DOI: 10.1016/j.devcel.2013.10.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 09/12/2013] [Accepted: 10/09/2013] [Indexed: 01/25/2023]
Abstract
Cytokinins (CKs), a class of plant hormones, are central regulators of plant growth and development. Based on numerous physiological and genetic studies, the quantitative regulation of cytokinin levels is the major mechanism regulating cytokinin action in diverse developmental processes. Here, we identified a different mechanism with which the physiological function of CK is modulated through side-chain modification (trans-hydroxylation). The trans-hydroxylation that forms trans-zeatin (tZ)-type CK from N(6)-(Δ(2)-isopentenyl)adenine (iP)-type CK is catalyzed by the cytochrome P450 enzymes CYP735A1 and CYP735A2 in Arabidopsis. Deficiency in trans-hydroxylation activity results in dramatic retardation of shoot growth without affecting total CK quantity, while augmentation of the activity enhances shoot growth. Application of exogenous tZ but not iP recovers the wild-type phenotype in the mutants, indicating that trans-hydroxylation modifies the physiological function of CK. We propose that the control of cytokinin function by side-chain modification is crucial for shoot growth regulation in plants.
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Affiliation(s)
- Takatoshi Kiba
- RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama 230-0045, Japan
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81
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Abstract
Cytokinins are N (6) substituted adenine derivatives that affect many aspects of plant growth and development, including cell division, shoot initiation and growth, leaf senescence, apical dominance, sink/source relationships, nutrient uptake, phyllotaxis, and vascular, gametophyte, and embryonic development, as well as the response to biotic and abiotic factors. Molecular genetic studies in Arabidopsis have helped elucidate the mechanisms underlying the function of this phytohormone in plants. Here, we review our current understanding of cytokinin biosynthesis and signaling in Arabidopsis, the latter of which is similar to bacterial two-component phosphorelays. We discuss the perception of cytokinin by the ER-localized histidine kinase receptors, the role of the AHPs in mediating the transfer of the phosphoryl group from the receptors to the response regulators (ARRs), and finally the role of the large ARR family in cytokinin function. The identification and genetic manipulation of the genes involved in cytokinin metabolism and signaling have helped illuminate the roles of cytokinins in Arabidopsis. We discuss these diverse roles, and how other signaling pathways influence cytokinin levels and sensitivity though modulation of the expression of cytokinin signaling and metabolic genes.
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Affiliation(s)
- Joseph J Kieber
- University of North Carolina, Biology Department, Chapel Hill, NC 27599-3280
| | - G Eric Schaller
- Dartmouth College, Department of Biological Sciences, Hanover, NH 03755
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82
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Zalabák D, Galuszka P, Mrízová K, Podlešáková K, Gu R, Frébortová J. Biochemical characterization of the maize cytokinin dehydrogenase family and cytokinin profiling in developing maize plantlets in relation to the expression of cytokinin dehydrogenase genes. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 74:283-93. [PMID: 24333683 DOI: 10.1016/j.plaphy.2013.11.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 11/19/2013] [Indexed: 05/18/2023]
Abstract
The cytokinin dehydrogenases (CKX; EC 1.5.99.12) are a protein family that maintains the endogenous levels of cytokinins in plants by catalyzing their oxidative degradation. The CKX family in maize (Zea mays L.) has thirteen members, only two of which--ZmCKX1 and ZmCKX10--have previously been characterized in detail. In this study, nine further maize CKX isoforms were heterologously expressed in Escherichia coli, purified by affinity and ion-exchange chromatography and biochemically characterized. ZmCKX6 and ZmCKX9 could only be expressed successfully after the removal of putative sequence-specific vacuolar sorting signals (LLPT and LPTS, respectively), suggesting that these proteins are localized to the vacuole. Substrate specificity analyses revealed that the CKX isoforms can be grouped into two subfamilies: members of the first strongly prefer cytokinin free bases while members of the second degrade a broad range of substrates. The most active isoform was found to be ZmCKX1. One of the studied isoforms, ZmCKX6, seemed to encode a nonfunctional enzyme due to a mutation in a conserved HFG protein domain at the C-terminus. Site-directed mutagenesis experiments revealed that this domain is essential for CKX activity. The roles of the maize CKX enzymes in the development of maize seedlings during the two weeks immediately after radicle emergence were also investigated. It appears that ZmCKX1 is a key regulator of active cytokinin levels in developing maize roots. However, the expression of individual CKX isoforms in the shoots varied and none of them seemed to have strong effects on the cytokinin pool.
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Affiliation(s)
- David Zalabák
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Molecular Biology, Šlechtitelů 11, Olomouc 783 71, Czech Republic.
| | - Petr Galuszka
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Molecular Biology, Šlechtitelů 11, Olomouc 783 71, Czech Republic.
| | - Katarina Mrízová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Molecular Biology, Šlechtitelů 11, Olomouc 783 71, Czech Republic.
| | - Kateřina Podlešáková
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Chemical Biology and Genetics, Šlechtitelů 11, Olomouc 783 71, Czech Republic.
| | - Riliang Gu
- Key Lab of Plant Nutrition, MOA, College of Resources and Environmental Science, China Agricultural University, 100193 Beijing, China.
| | - Jitka Frébortová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Chemical Biology and Genetics, Šlechtitelů 11, Olomouc 783 71, Czech Republic.
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83
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Hann DR, Domínguez-Ferreras A, Motyka V, Dobrev PI, Schornack S, Jehle A, Felix G, Chinchilla D, Rathjen JP, Boller T. The Pseudomonas type III effector HopQ1 activates cytokinin signaling and interferes with plant innate immunity. THE NEW PHYTOLOGIST 2014; 201:585-598. [PMID: 24124900 DOI: 10.1111/nph.12544] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/02/2013] [Indexed: 05/26/2023]
Abstract
We characterized the molecular function of the Pseudomonas syringae pv. tomato DC3000 (Pto) effector HopQ1. In silico studies suggest that HopQ1 might possess nucleoside hydrolase activity based on the presence of a characteristic aspartate motif. Transgenic Arabidopsis lines expressing HopQ1 or HopQ1 aspartate mutant variants were characterized with respect to flagellin triggered immunity, phenotype and changes in phytohormone content by high-performance liquid chromatography-MS (HPLC-MS). We found that HopQ1, but not its aspartate mutants, suppressed all tested immunity marker assays. Suppression of immunity was the result of a lack of the flagellin receptor FLS2, whose gene expression was abolished by HopQ1 in a promoter-dependent manner. Furthermore, HopQ1 induced cytokinin signaling in Arabidopsis and the elevation in cytokinin signaling appears to be responsible for the attenuation of FLS2 expression. We conclude that HopQ1 can activate cytokinin signaling and that moderate activation of cytokinin signaling leads to suppression of FLS2 accumulation and thus defense signaling.
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Affiliation(s)
- Dagmar R Hann
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - Ana Domínguez-Ferreras
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - Vaclav Motyka
- Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic
| | - Petre I Dobrev
- Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic
| | | | - Anna Jehle
- Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany
| | - Georg Felix
- Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany
| | - Delphine Chinchilla
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - John P Rathjen
- The Australian National University, The Linnaeus Building, Building 134, Linnaeus Way, Canberra, ACT, 0200, Australia
| | - Thomas Boller
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
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84
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Abstract
Functional distinction between structurally diverse cytokinins as essential plant hormones has remained enigmatic for decades. In this issue of Developmental Cell, Kiba et al. (2013) provide compelling evidence for the central role of CYP735A1/2 in synthesizing trans-hydroxylated cytokinins, which specify shoot growth, vital for energy and biomass production.
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Affiliation(s)
- Jen Sheen
- Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
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85
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Černý M, Kuklová A, Hoehenwarter W, Fragner L, Novák O, Rotková G, Jedelský PL, Žáková K, Šmehilová M, Strnad M, Weckwerth W, Brzobohatý B. Proteome and metabolome profiling of cytokinin action in Arabidopsis identifying both distinct and similar responses to cytokinin down- and up-regulation. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:4193-206. [PMID: 24064926 PMCID: PMC3808309 DOI: 10.1093/jxb/ert227] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In plants, numerous developmental processes are controlled by cytokinin (CK) levels and their ratios to levels of other hormones. While molecular mechanisms underlying the regulatory roles of CKs have been intensely researched, proteomic and metabolomic responses to CK deficiency are unknown. Transgenic Arabidopsis seedlings carrying inducible barley cytokinin oxidase/dehydrogenase (CaMV35S>GR>HvCKX2) and agrobacterial isopentenyl transferase (CaMV35S>GR>ipt) constructs were profiled to elucidate proteome- and metabolome-wide responses to down- and up-regulation of CK levels, respectively. Proteome profiling identified >1100 proteins, 155 of which responded to HvCKX2 and/or ipt activation, mostly involved in growth, development, and/or hormone and light signalling. The metabolome profiling covered 79 metabolites, 33 of which responded to HvCKX2 and/or ipt activation, mostly amino acids, carbohydrates, and organic acids. Comparison of the data sets obtained from activated CaMV35S>GR>HvCKX2 and CaMV35S>GR>ipt plants revealed unexpectedly extensive overlaps. Integration of the proteomic and metabolomic data sets revealed: (i) novel components of molecular circuits involved in CK action (e.g. ribosomal proteins); (ii) previously unrecognized links to redox regulation and stress hormone signalling networks; and (iii) CK content markers. The striking overlaps in profiles observed in CK-deficient and CK-overproducing seedlings might explain surprising previously reported similarities between plants with down- and up-regulated CK levels.
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Affiliation(s)
- Martin Černý
- Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR and CEITEC–Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
| | - Alena Kuklová
- Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR and CEITEC–Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
| | - Wolfgang Hoehenwarter
- Department of Molecular Systems Biology (MOSYS), University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
- *Present address: Proteome Analysis Research Group, Leibniz Institute of Plant Biochemistry, D-06120 Halle, Germany
| | - Lena Fragner
- Department of Molecular Systems Biology (MOSYS), University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Ondřej Novák
- Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, CZ-78371 Olomouc, Czech Republic
| | - Gabriela Rotková
- Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR and CEITEC–Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
| | - Petr L. Jedelský
- Department of Cell Biology, Faculty of Science, Charles University, Viničná 7, CZ-128 43 Prague, Czech Republic
| | - Kateřina Žáková
- Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR and CEITEC–Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
| | - Mária Šmehilová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Molecular Biology, Faculty of Science, Palacký University, Šlechtitelů 11, CZ-78371 Olomouc, Czech Republic
| | - Miroslav Strnad
- Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, CZ-78371 Olomouc, Czech Republic
| | - Wolfram Weckwerth
- Department of Molecular Systems Biology (MOSYS), University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Břetislav Brzobohatý
- Laboratory of Plant Molecular Biology, Institute of Biophysics AS CR and CEITEC–Central European Institute of Technology, Mendel University in Brno, Zemědělská 1, CZ-613 00 Brno, Czech Republic
- To whom correspondence should be addressed. E-mail:
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86
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Chang L, Ramireddy E, Schmülling T. Lateral root formation and growth of Arabidopsis is redundantly regulated by cytokinin metabolism and signalling genes. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5021-32. [PMID: 24023250 PMCID: PMC3830484 DOI: 10.1093/jxb/ert291] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The plant root system is important for the uptake of water and nutrients and the anchoring of plants in the soil. Lateral roots (LRs) contribute considerably to root system architecture. Their post-embryonic formation is regulated by hormones and environmental cues. The hormone cytokinin influences LR formation and growth in Arabidopsis thaliana on different levels by disturbing cell division activity and pattern formation. This includes inhibition of the first formative cell division of pericycle founder cells and inhibition of the outgrowth of young LR primordia. Mutant analysis revealed that the cytokinin biosynthesis genes IPT3 and IPT5 and all three cytokinin receptor genes (AHK2, AHK3, and CRE1/AHK4) act redundantly during LR initiation. Mutation of AHK2 and AHK3 caused increased auxin sensitivity of LR formation, corroborating the functional relevance of auxin-cytokinin interaction during LR formation. In contrast, LR development of cytokinin receptor mutants in response to other hormones was mostly similar to that of the wild type, which is consistent with separate response pathways. A noticeable exception was an increased sensitivity of LR elongation to brassinolide in ahk2 ahk3 mutants indicating antagonistic action of cytokinin and brassinosteroid. It is proposed that the multilevel redundancy of the cytokinin system in modulating LR formation reflects its role in mediating environmental cues.
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87
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Gruhn N, Heyl A. Updates on the model and the evolution of cytokinin signaling. CURRENT OPINION IN PLANT BIOLOGY 2013; 16:569-74. [PMID: 24080474 DOI: 10.1016/j.pbi.2013.09.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 09/02/2013] [Accepted: 09/02/2013] [Indexed: 05/09/2023]
Abstract
Cytokinins represent a class of phytohormones, which are key players not only in many processes important for plant growth and development, but also in the response to changes in their environment. The model for the cytokinin signaling pathway was established at the turn of the last century and many experiments confirmed its validity. In recent years several changes and extensions to the model were necessary to accommodate new findings concerning its components, such as subcellular localization, selective protein degradation and new modes of cross talk. In addition phylogenetic analyses of components of the cytokinin circuitry started to reveal the origin and evolution of the cytokinin regulatory system.
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Affiliation(s)
- Nijuscha Gruhn
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Germany
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88
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Steklov MY, Lomin SN, Osolodkin DI, Romanov GA. Structural basis for cytokinin receptor signaling: an evolutionary approach. PLANT CELL REPORTS 2013; 32:781-93. [PMID: 23525743 DOI: 10.1007/s00299-013-1408-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 02/27/2013] [Accepted: 03/01/2013] [Indexed: 05/10/2023]
Abstract
Cytokinins are ubiquitous plant hormones; their signal is perceived by sensor histidine kinases-cytokinin receptors. This review focuses on recent advances on cytokinin receptor structure, in particular sensing module and adjacent domains which play an important role in hormone recognition, signal transduction and receptor subcellular localization. Principles of cytokinin binding site organization and point mutations affecting signaling are discussed. To date, more than 100 putative cytokinin receptor genes from different plant species were revealed due to the total genome sequencing. This allowed us to employ an evolutionary and bioinformatics approaches to clarify some new aspects of receptor structure and function. Non-transmembrane areas adjacent to the ligand-binding CHASE domain were characterized in detail and new conserved protein motifs were recovered. Putative mechanisms for cytokinin-triggered receptor activation were suggested.
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Affiliation(s)
- Mikhail Yu Steklov
- K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow, Russia
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89
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Jin SH, Ma XM, Kojima M, Sakakibara H, Wang YW, Hou BK. Overexpression of glucosyltransferase UGT85A1 influences trans-zeatin homeostasis and trans-zeatin responses likely through O-glucosylation. PLANTA 2013; 237:991-999. [PMID: 23187681 DOI: 10.1007/s00425-012-1818-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 11/16/2012] [Indexed: 05/18/2023]
Abstract
Trans-zeatin is a kind of cytokinins that plays a crucial role in plant growth and development. The master trans-zeatin O-glucosyltransferase of Arabidopsis thaliana, UGT85A1, has been previously identified through biochemical approach. To determine the in planta role of UGT85A1 gene, the characterization of transgenic Arabidopsis plants overexpressing UGT85A1 was carried out. Under normal conditions, transgenic Arabidopsis did not display clearly altered phenotypes. A remarkable alteration is that the accumulation level of the trans-zeatin O-glucosides was significantly increased in UGT85A1 overexpressing transgenic Arabidopsis, while other forms of cytokinins kept the similar concentrations compared to the wild type. When treated with exogenously applied trans-zeatin, UGT85A1 overexpressing Arabidopsis showed much less sensitivity to trans-zeatin in primary root elongation and lateral root formation. Meanwhile, the chlorophyll content of detached leaves of transgenic Arabidopsis was much lower than wild type. Studies of spatial-temporal expression patterns showed that UGT85A1 was mainly expressed in the early seedlings and developing seeds. Analysis of subcellular localization suggested that UGT85A1 was localized to cytoplasm and nucleus. Taken together, our data suggest that overexpression of Arabidopsis glucosyltransferase UGT85A1 influences trans-zeatin homeostasis and trans-zeatin responses likely through O-glucosylation in planta.
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Affiliation(s)
- Shang-Hui Jin
- The Key Lab of Plant Cell Engineering and Germplasm Innovation, Education Ministry of China, Jinan, 250100, Shandong, People's Republic of China
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90
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Nongpiur R, Soni P, Karan R, Singla-Pareek SL, Pareek A. Histidine kinases in plants: cross talk between hormone and stress responses. PLANT SIGNALING & BEHAVIOR 2012; 7:1230-7. [PMID: 22902699 PMCID: PMC3493402 DOI: 10.4161/psb.21516] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Two-component signaling pathways involve sensory histidine kinases (HK), histidine phosphotransfer proteins (HpT) and response regulators (RR). Recent advancements in genome sequencing projects for a number of plant species have established the TCS family to be multigenic one. In plants, HKs operate through the His-Asp phosphorelay and control many physiological and developmental processes throughout the lifecycle of plants. Despite the huge diversity reported for the structural features of the HKs, their functional redundancy has also been reported via mutant approach. Several sensory HKs having a CHASE domain, transmembrane domain(s), transmitter domain and receiver domain have been reported to be involved in cytokinin and ethylene signaling. On the other hand, there are also increasing evidences for some of the sensory HKs to be performing their role as osmosensor, clearly indicating toward a possible cross-talk between hormone and stress responsive cascades. In this review, we bring out the latest knowledge about the structure and functions of histidine kinases in cytokinin and ethylene signaling and their role(s) in development and the regulation of environmental stress responses.
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Affiliation(s)
- Ramsong Nongpiur
- Stress Physiology and Molecular Biology Laboratory; School of Life Sciences: Jawaharlal Nehru University; New Delhi, India
| | - Praveen Soni
- Stress Physiology and Molecular Biology Laboratory; School of Life Sciences: Jawaharlal Nehru University; New Delhi, India
| | - Ratna Karan
- Stress Physiology and Molecular Biology Laboratory; School of Life Sciences: Jawaharlal Nehru University; New Delhi, India
| | - Sneh L. Singla-Pareek
- Plant Molecular Biology; International Centre for Genetic Engineering and Biotechnology; New Delhi, India
| | - Ashwani Pareek
- Stress Physiology and Molecular Biology Laboratory; School of Life Sciences: Jawaharlal Nehru University; New Delhi, India
- Correspondence to: Ashwani Pareek,
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91
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Kudo T, Makita N, Kojima M, Tokunaga H, Sakakibara H. Cytokinin activity of cis-zeatin and phenotypic alterations induced by overexpression of putative cis-Zeatin-O-glucosyltransferase in rice. PLANT PHYSIOLOGY 2012; 160:319-31. [PMID: 22811434 PMCID: PMC3440209 DOI: 10.1104/pp.112.196733] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
cis-Zeatin (cZ) is generally regarded as a cytokinin with little or no activity, compared with the highly active trans-zeatin (tZ). Although recent studies suggested possible roles for cZ, its physiological significance remains unclear. In our studies with rice (Oryza sativa), cZ inhibited seminal root elongation and up-regulated cytokinin-inducible genes, and its activities were comparable to those of tZ. Tracer experiments showed that exogenously supplied cZ-riboside was mainly converted into cZ derivatives but scarcely into tZ derivatives, indicating that isomerizations of cZ derivatives into tZ derivatives are a minor pathway in rice cytokinin metabolism. We identified three putative cZ-O-glucosyltransferases (cZOGT1, cZOGT2, and cZOGT3) in rice. The cZOGTs preferentially catalyzed O-glucosylation of cZ and cZ-riboside rather than tZ and tZ-riboside in vitro. Transgenic rice lines ectopically overexpressing the cZOGT1 and cZOGT2 genes exhibited short-shoot phenotypes, delay of leaf senescence, and decrease in crown root number, while cZOGT3 overexpressor lines did not show shortened shoots. These results propose that cZ activity has a physiological impact on the growth and development of rice.
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92
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Matsuo S, Kikuchi K, Fukuda M, Honda I, Imanishi S. Roles and regulation of cytokinins in tomato fruit development. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:5569-79. [PMID: 22865911 PMCID: PMC3444270 DOI: 10.1093/jxb/ers207] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Cytokinins (CKs) are thought to play important roles in fruit development, especially cell division. However, the mechanisms and regulation of CK activity have not been well investigated. This study analysed CK concentrations and expression of genes involved in CK metabolism in developing tomato (Solanum lycopersicum) ovaries. The concentrations of CK ribosides and isopentenyladenine and the transcript levels of the CK biosynthetic genes SlIPT3, SlIPT4, SlLOG6, and SlLOG8 were high at anthesis and decreased immediately afterward. In contrast, trans-zeatin concentration and the transcript levels of the CK biosynthetic genes SlIPT1, SlIPT2, SlCYP735A1, SlCYP735A2, and SlLOG2 increased after anthesis. The expression of type-A response regulator genes was high in tomato ovaries from pre-anthesis to early post-anthesis stages. These results suggest that the CK signal transduction pathway is active in the cell division phase of fruit development. This study also investigated the effect of CK application on fruit set and development. Application of a synthetic CK, N-(2-chloro-pyridin-4-yl)-N'-phenylurea (CPPU), to unpollinated tomato ovaries induced parthenocarpic fruit development. The CPPU-induced parthenocarpic fruits were smaller than pollinated fruits, because of reduction of pericarp cell size rather than reduced cell number. Thus, CPPU-induced parthenocarpy was attributable to the promotion of cell division, not cell expansion. Overall, the results provide evidence that CKs are involved in cell division during development of tomato fruit.
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Affiliation(s)
- Satoshi Matsuo
- NARO Institute of Vegetable and Tea Science, National Agriculture and Food Research Organization (NARO), 360 Kusawa, Ano, Tsu, Mie 514-2392 Japan.
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93
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Krivosheev DM, Kolyachkina SV, Mikhailov SN, Tararov VI, Vanyushin BF, Romanov GA. N6-(benzyloxymethyl)adenosine is a novel anticytokinin, an antagonist of cytokinin receptor CRE1/AHK4 of Arabidopsis. DOKL BIOCHEM BIOPHYS 2012; 444:178-81. [DOI: 10.1134/s1607672912030155] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Indexed: 11/23/2022]
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94
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Shi X, Rashotte AM. Advances in upstream players of cytokinin phosphorelay: receptors and histidine phosphotransfer proteins. PLANT CELL REPORTS 2012; 31:789-99. [PMID: 22350315 DOI: 10.1007/s00299-012-1229-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 01/13/2012] [Accepted: 01/14/2012] [Indexed: 05/09/2023]
Abstract
Cytokinins are a class of plant hormones that have been linked to numerous growth and developmental aspects in plants. The cytokinin signal is perceived by sensor histidine kinase receptors and transmitted via histidine phosphotransfer proteins (HPts) to downstream response regulators. Since their discovery, cytokinin receptors have been a focus of interest for many researchers. Ongoing research on these transmembrane receptors has greatly broadened our knowledge in terms of cytokinin-receptor interaction, receptor specificity, receptor cellular localization, and receptor functions in cytokinin related growth and developmental processes. This review focuses on the recent advances on the cytokinin receptors and HPt proteins in Arabidopsis.
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Affiliation(s)
- Xiuling Shi
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
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95
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Sp Chal LX. Cytokinins - recent news and views of evolutionally old molecules. FUNCTIONAL PLANT BIOLOGY : FPB 2012; 39:267-284. [PMID: 32480780 DOI: 10.1071/fp11276] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 03/06/2012] [Indexed: 05/03/2023]
Abstract
Cytokinins (CKs) are evolutionally old and highly conserved low-mass molecules that have been identified in almost all known organisms. In plants, they evolved into an important group of plant hormones controlling many physiological and developmental processes throughout the whole lifespan of the plant. CKs and their functions are, however, not unique to plants. In this review, the strategies and mechanisms of plants - and phylogenetically distinct plant-interacting organisms such as bacteria, fungi, nematodes and insects employing CKs or regulation of CK status in plants - are described and put into their evolutionary context. The major breakthroughs made in the last decade in the fields of CK biosynthesis, degradation and signalling are also summarised.
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Affiliation(s)
- Luk X Sp Chal
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, CZ-78371 Olomouc, Czech Republic. Email
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96
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Vescovi M, Riefler M, Gessuti M, Novák O, Schmülling T, Lo Schiavo F. Programmed cell death induced by high levels of cytokinin in Arabidopsis cultured cells is mediated by the cytokinin receptor CRE1/AHK4. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:2825-32. [PMID: 22312114 PMCID: PMC3346239 DOI: 10.1093/jxb/ers008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
High levels of cytokinins (CKs) induce programmed cell death (PCD) both in animals and plant cells. High levels of the CK benzylaminopurine (BA) induce PCD in cultured cells of Arabidopsis thaliana by accelerating a senescence process characterized by DNA laddering and expression of a specific senescence marker. In this report, the question has been addressed whether members of the small family of Arabidopsis CK receptors (AHK2, AHK3, CRE1/AHK4) are required for BA-induced PCD. In this respect, suspension cell cultures were produced from selected receptor mutants. Cell growth and proliferation of all receptor mutant and wild-type cell cultures were similar, showing that the CK receptors are not required for these processes in cultured cells. The analysis of CK metabolites instead revealed differences between wild-type and receptor mutant lines, and indicated that all three receptors are redundantly involved in the regulation of the steady-state levels of isopentenyladenine- and trans-zeatin-type CKs. By contrast, the levels of cis-zeatin-type CKs were controlled mainly by AHK2 and AHK3. To study the role of CK receptors in the BA-induced PCD pathway, cultured cells were analysed for their behaviour in the presence of high levels of BA. The results show that CRE1/AHK4, the strongest expressed CK receptor gene of this family in cultured cells, is required for PCD, thus linking this process to the known CK signalling pathway.
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Affiliation(s)
- Marco Vescovi
- Dipartimento di Biologia, Università Degli Studi di Padova, Via G. Colombo 3, I-35121 Padua, Italy
| | - Michael Riefler
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Micael Gessuti
- Dipartimento di Biologia, Università Degli Studi di Padova, Via G. Colombo 3, I-35121 Padua, Italy
| | - Ondřej Novák
- Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, CZ-78371 Olomouc, Czech Republic
| | - Thomas Schmülling
- Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Fiorella Lo Schiavo
- Dipartimento di Biologia, Università Degli Studi di Padova, Via G. Colombo 3, I-35121 Padua, Italy
- To whom correspondence should be addressed. E-mail:
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97
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Ha S, Vankova R, Yamaguchi-Shinozaki K, Shinozaki K, Tran LSP. Cytokinins: metabolism and function in plant adaptation to environmental stresses. TRENDS IN PLANT SCIENCE 2012; 17:172-9. [PMID: 22236698 DOI: 10.1016/j.tplants.2011.12.005] [Citation(s) in RCA: 268] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/06/2011] [Accepted: 12/12/2011] [Indexed: 05/18/2023]
Abstract
In plants, the cytokinin (CK) phytohormones regulate numerous biological processes, including responses to environmental stresses, via a complex network of CK signaling. By an unknown mechanism, stress signals are perceived and transmitted through the His-Asp phosphorelay, an important component of the CK signal transduction pathway, triggering CK-responsive genes. Because of the intensive crosstalk between CKs and abscisic acid (ABA), modulation of CK levels and their signal transduction affects both ABA-dependent and ABA-independent pathways, enabling plant adaptation to adverse conditions. This review presents our current understanding of the functions of CKs and CK signaling in the regulation of plant adaptation to stress. Biotechnological strategies based on the modulation of CK levels have been examined with the aim of stabilizing agriculture yields.
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Affiliation(s)
- Sukbong Ha
- Department of Plant Biotechnology, Chonnam National University, Buk-Gu, Gwangju 500-757, Korea
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Argueso CT, Ferreira FJ, Epple P, To JPC, Hutchison CE, Schaller GE, Dangl JL, Kieber JJ. Two-component elements mediate interactions between cytokinin and salicylic acid in plant immunity. PLoS Genet 2012; 8:e1002448. [PMID: 22291601 PMCID: PMC3266875 DOI: 10.1371/journal.pgen.1002448] [Citation(s) in RCA: 145] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 11/16/2011] [Indexed: 11/19/2022] Open
Abstract
Recent studies have revealed an important role for hormones in plant immunity. We are now beginning to understand the contribution of crosstalk among different hormone signaling networks to the outcome of plant–pathogen interactions. Cytokinins are plant hormones that regulate development and responses to the environment. Cytokinin signaling involves a phosphorelay circuitry similar to two-component systems used by bacteria and fungi to perceive and react to various environmental stimuli. In this study, we asked whether cytokinin and components of cytokinin signaling contribute to plant immunity. We demonstrate that cytokinin levels in Arabidopsis are important in determining the amplitude of immune responses, ultimately influencing the outcome of plant–pathogen interactions. We show that high concentrations of cytokinin lead to increased defense responses to a virulent oomycete pathogen, through a process that is dependent on salicylic acid (SA) accumulation and activation of defense gene expression. Surprisingly, treatment with lower concentrations of cytokinin results in increased susceptibility. These functions for cytokinin in plant immunity require a host phosphorelay system and are mediated in part by type-A response regulators, which act as negative regulators of basal and pathogen-induced SA–dependent gene expression. Our results support a model in which cytokinin up-regulates plant immunity via an elevation of SA–dependent defense responses and in which SA in turn feedback-inhibits cytokinin signaling. The crosstalk between cytokinin and SA signaling networks may help plants fine-tune defense responses against pathogens. Plant hormones play an important role in many aspects of a plant's life cycle, from the regulation of development to responses to constantly changing environmental conditions. In the past decade, the importance of hormones in plant immunity against a variety of pathogens has been uncovered. In this manuscript, we demonstrate that in the model plant species Arabidopsis thaliana components of the signaling system of the plant hormone cytokinin also mediate plant immunity. We demonstrate that this involves the type-A class of Arabidopsis response regulators in a process that occurs downstream of the plant defense hormone salicylic acid and involves a host two-component phosphorelay. Moreover, we show that the levels of cytokinin are important in determining the amplitude of plant immunity, ultimately influencing the outcome of plant–pathogen interactions. Finally, our results indicate that salicylic acid negatively regulates cytokinin signaling, which may serve to fine-tune the effects of cytokinin in plant immunity. Given the high energy costs of defense responses and the role of cytokinins in carbon partitioning and energy allocation, we hypothesize that the mechanisms uncovered here may help regulate the levels of energy that can be allocated into defense responses, an important aspect in the biology of plants.
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Affiliation(s)
- Cristiana T. Argueso
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Fernando J. Ferreira
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Petra Epple
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Howard Hughes Medical Institute, Chapel Hill, North Carolina, United States of America
| | - Jennifer P. C. To
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Claire E. Hutchison
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - G. Eric Schaller
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America
| | - Jeffery L. Dangl
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Howard Hughes Medical Institute, Chapel Hill, North Carolina, United States of America
| | - Joseph J. Kieber
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
- * E-mail:
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99
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Abstract
Despite long-standing observations on diverse cytokinin actions, the discovery path to cytokinin signaling mechanisms was tortuous. Unyielding to conventional genetic screens, experimental innovations were paramount in unraveling the core cytokinin signaling circuitry, which employs a large repertoire of genes with overlapping and specific functions. The canonical two-component transcription circuitry involves His kinases that perceive cytokinin and initiate signaling, as well as His-to-Asp phosphorelay proteins that transfer phosphoryl groups to response regulators, transcriptional activators, or repressors. Recent advances have revealed the complex physiological functions of cytokinins, including interactions with auxin and other signal transduction pathways. This review begins by outlining the historical path to cytokinin discovery and then elucidates the diverse cytokinin functions and key signaling components. Highlights focus on the integration of cytokinin signaling components into regulatory networks in specific contexts, ranging from molecular, cellular, and developmental regulations in the embryo, root apical meristem, shoot apical meristem, stem and root vasculature, and nodule organogenesis to organismal responses underlying immunity, stress tolerance, and senescence.
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Affiliation(s)
- Ildoo Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Korea.
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100
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Tokunaga H, Kojima M, Kuroha T, Ishida T, Sugimoto K, Kiba T, Sakakibara H. Arabidopsis lonely guy (LOG) multiple mutants reveal a central role of the LOG-dependent pathway in cytokinin activation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 69:355-65. [PMID: 22059596 DOI: 10.1111/j.1365-313x.2011.04795.x] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Cytokinins are phytohormones that play key roles in the maintenance of stem cell activity in plants. Although alternative single-step and two-step activation pathways for cytokinin have been proposed, the significance of the single-step pathway which is catalyzed by LONELY GUY (LOG), is not fully understood. We analyzed the metabolic flow of cytokinin activation in Arabidopsis log multiple mutants using stable isotope-labeled tracers and characterized the mutants' morphological and developmental phenotypes. In tracer experiments, cytokinin activation was inhibited most pronouncedly by log7, while the other log mutations had cumulative effects. Although sextuple or lower-order mutants did not show drastic phenotypes in vegetative growth, the log1log2log3log4log5log7log8 septuple T-DNA insertion mutant in which the LOG-dependent pathway is impaired, displayed severe retardation of shoot and root growth with defects in the maintenance of the apical meristems. Detailed observation of the mutants showed that LOG7 was required for the maintenance of shoot apical meristem size. LOG7 was also suggested to play a role for normal primary root growth together with LOG3 and LOG4. These results suggest a dominant role of the single-step activation pathway mediated by LOGs for cytokinin production, and overlapping but differentiated functions of the members of the LOG gene family in growth and development.
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Affiliation(s)
- Hiroki Tokunaga
- RIKEN Plant Science Center, 1-7-22, Suehiro, Tsurumi, Yokohama 230-0045, Japan
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