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Luo F, Zhang Q, Xin H, Liu H, Yang H, Doblin MS, Bacic A, Li L. A Phytochrome B-PIF4-MYC2/MYC4 module inhibits secondary cell wall thickening in response to shaded light. PLANT COMMUNICATIONS 2022; 3:100416. [PMID: 35927944 PMCID: PMC9700123 DOI: 10.1016/j.xplc.2022.100416] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 06/21/2022] [Accepted: 07/25/2022] [Indexed: 06/01/2023]
Abstract
Secondary cell walls (SCWs) in stem cells provide mechanical strength and structural support for growth. SCW thickening varies under different light conditions. Our previous study revealed that blue light enhances SCW thickening through the redundant function of MYC2 and MYC4 directed by CRYPTOCHROME1 (CRY1) signaling in fiber cells of the Arabidopsis inflorescence stem. In this study, we find that the Arabidopsis PHYTOCHROME B mutant phyB displays thinner SCWs in stem fibers, but thicker SCWs are deposited in the PHYTOCHROME INTERACTING FACTOR (PIF) quadruple mutant pif1pif3pif4pif5 (pifq). The shaded light condition with a low ratio of red to far-red light inhibits stem SCW thickening. PIF4 interacts with MYC2 and MYC4 to affect their localization in nuclei, and this interaction results in inhibition of the MYCs' transactivation activity on the NST1 promoter. Genetic evidence shows that regulation of SCW thickening by PIFs is dependent on MYC2/MYC4 function. Together, the results of this study reveal a PHYB-PIF4-MYC2/MYC4 module that inhibits SCW thickening in fiber cells of the Arabidopsis stem.
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Affiliation(s)
- Fang Luo
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Qian Zhang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hu Xin
- Key Laboratory of Biodiversity Conservation in Southwest, State Forestry Administration, Southwest Forestry University, Kunming 650224, China
| | - Hongtao Liu
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Hongquan Yang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Monika S Doblin
- La Trobe Institute for Agriculture and Food, School of Agriculture, Biomedicine and Environment, Department of Animal, Plant and Soil Sciences, AgriBio, La Trobe University, Bundoora, VIC 3086, Australia; Sino-Australia Plant Cell Wall Research Centre, State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou 311300, China
| | - Antony Bacic
- La Trobe Institute for Agriculture and Food, School of Agriculture, Biomedicine and Environment, Department of Animal, Plant and Soil Sciences, AgriBio, La Trobe University, Bundoora, VIC 3086, Australia; Sino-Australia Plant Cell Wall Research Centre, State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou 311300, China
| | - Laigeng Li
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
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Farooq MA, Ma W, Shen S, Gu A. Underlying Biochemical and Molecular Mechanisms for Seed Germination. Int J Mol Sci 2022; 23:ijms23158502. [PMID: 35955637 PMCID: PMC9369107 DOI: 10.3390/ijms23158502] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 07/24/2022] [Accepted: 07/29/2022] [Indexed: 02/01/2023] Open
Abstract
With the burgeoning population of the world, the successful germination of seeds to achieve maximum crop production is very important. Seed germination is a precise balance of phytohormones, light, and temperature that induces endosperm decay. Abscisic acid and gibberellins—mainly with auxins, ethylene, and jasmonic and salicylic acid through interdependent molecular pathways—lead to the rupture of the seed testa, after which the radicle protrudes out and the endosperm provides nutrients according to its growing energy demand. The incident light wavelength and low and supra-optimal temperature modulates phytohormone signaling pathways that induce the synthesis of ROS, which results in the maintenance of seed dormancy and germination. In this review, we have summarized in detail the biochemical and molecular processes occurring in the seed that lead to the germination of the seed. Moreover, an accurate explanation in chronological order of how phytohormones inside the seed act in accordance with the temperature and light signals from outside to degenerate the seed testa for the thriving seed’s germination has also been discussed.
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3
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Liu S, Yang L, Li J, Tang W, Li J, Lin R. FHY3 interacts with phytochrome B and regulates seed dormancy and germination. PLANT PHYSIOLOGY 2021; 187:289-302. [PMID: 33764465 PMCID: PMC8418400 DOI: 10.1093/plphys/kiab147] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/12/2021] [Indexed: 05/11/2023]
Abstract
Seed dormancy and germination are fundamental processes for plant propagation, both of which are tightly regulated by internal and external cues. Phytochrome B (phyB) is a major red/far-red-absorbing photoreceptor that senses light signals that modulate seed dormancy and germination. However, the components that directly transduce that signal downstream of phyB are mostly unknown. Here, we show that the transposase-derived transcription factor FAR-RED ELONGATED HYPOCOTYL3 (FHY3) inhibits seed dormancy and promotes phyB-mediated seed germination in Arabidopsis thaliana. FHY3 physically interacts with phyB in vitro and in vivo. RNA-sequencing and reverse transcription-quantitative polymerase chain reaction analyses showed that FHY3 regulates multiple downstream genes, including REVEILLE2 (RVE2), RVE7, and SPATULA (SPT). Yeast one-hybrid, electrophoresis mobility shift, and chromatin immunoprecipitation assays demonstrated that FHY3 directly binds these genes via a conserved FBS cis-element in their promoters. Furthermore, RVE2, RVE7, and GIBBERELLIN 3-OXIDASE 2 (GA3ox2) genetically act downstream of FHY3. Strikingly, light and phyB promote FHY3 protein accumulation. Our study reveals a transcriptional cascade consisting of phyB-FHY3-RVE2/RVE7/SPT-GA3ox2 that relays environmental light signals and thereby controls seed dormancy and germination.
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Affiliation(s)
- Shuangrong Liu
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liwen Yang
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jialong Li
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Weijiang Tang
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jigang Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Rongcheng Lin
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Author for communication:
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4
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Huber M, Nieuwendijk NM, Pantazopoulou CK, Pierik R. Light signalling shapes plant-plant interactions in dense canopies. PLANT, CELL & ENVIRONMENT 2021; 44:1014-1029. [PMID: 33047350 PMCID: PMC8049026 DOI: 10.1111/pce.13912] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/06/2020] [Accepted: 10/07/2020] [Indexed: 05/09/2023]
Abstract
Plants growing at high densities interact via a multitude of pathways. Here, we provide an overview of mechanisms and functional consequences of plant architectural responses initiated by light cues that occur in dense vegetation. We will review the current state of knowledge about shade avoidance, as well as its possible applications. On an individual level, plants perceive neighbour-associated changes in light quality and quantity mainly with phytochromes for red and far-red light and cryptochromes and phototropins for blue light. Downstream of these photoreceptors, elaborate signalling and integration takes place with the PHYTOCHROME INTERACTING FACTORS, several hormones and other regulators. This signalling leads to the shade avoidance responses, consisting of hyponasty, stem and petiole elongation, apical dominance and life cycle adjustments. Architectural changes of the individual plant have consequences for the plant community, affecting canopy structure, species composition and population fitness. In this context, we highlight the ecological, evolutionary and agricultural importance of shade avoidance.
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Affiliation(s)
- Martina Huber
- Plant Ecophysiology, Dept. BiologyUtrecht UniversityUtrechtThe Netherlands
| | | | | | - Ronald Pierik
- Plant Ecophysiology, Dept. BiologyUtrecht UniversityUtrechtThe Netherlands
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5
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Jenness MK, Tayengwa R, Murphy AS. An ATP-Binding Cassette Transporter, ABCB19, Regulates Leaf Position and Morphology during Phototropin1-Mediated Blue Light Responses. PLANT PHYSIOLOGY 2020; 184:1601-1612. [PMID: 32855213 PMCID: PMC7608178 DOI: 10.1104/pp.20.00223] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 08/18/2020] [Indexed: 05/25/2023]
Abstract
Blue light regulates multiple processes that optimize light capture and gas exchange in plants, including chloroplast movement, changes in stomatal conductance, and altered organ positioning. In Arabidopsis (Arabidopsis thaliana), these processes are primarily modulated by the blue light phototropin photoreceptors phot1 and phot2. Changes in leaf positioning and shape involve several signaling components that include NON-PHOTOTROPIC HYPOCOTYL3, PHYTOCHROME KINASE SUBSTRATE, ROOT PHOTOTROPISM2, and alterations in localized auxin streams. Direct phosphorylation of the auxin transporter ATP-BINDING CASSETTE subfamily B19 (ABCB19) by phot1 in phototropic seedlings suggests that phot1 may directly regulate ABCB19 to adjust auxin-dependent leaf responses. Here, abcb19 mutants were analyzed for fluence and blue light-dependent changes in leaf positioning and morphology. abcb19 displays upright petiole angles that remain unchanged in response to red and blue light. Similarly, abcb19 mutants develop irregularly wavy rosette leaves that are less sensitive to blue light-mediated leaf flattening. Visualization of auxin distribution, measurement of auxin transport in protoplasts, and direct quantification of free auxin levels suggest these irregularities are caused by misregulation of ABCB19-mediated auxin distribution in addition to light-dependent auxin biosynthesis.
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Affiliation(s)
- Mark K Jenness
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20740
| | - Reuben Tayengwa
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20740
| | - Angus S Murphy
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20740
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6
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Yang L, Liu S, Lin R. The role of light in regulating seed dormancy and germination. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2020; 62:1310-1326. [PMID: 32729981 DOI: 10.1111/jipb.13001] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/29/2020] [Indexed: 05/22/2023]
Abstract
Seed dormancy is an adaptive trait in plants. Breaking seed dormancy determines the timing of germination and is, thereby essential for ensuring plant survival and agricultural production. Seed dormancy and the subsequent germination are controlled by both internal cues (mainly hormones) and environmental signals. In the past few years, the roles of plant hormones in regulating seed dormancy and germination have been uncovered. However, we are only beginning to understand how light signaling pathways modulate seed dormancy and interaction with endogenous hormones. In this review, we summarize current views of the molecular mechanisms by which light controls the induction, maintenance and release of seed dormancy, as well as seed germination, by regulating hormone metabolism and signaling pathways.
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Affiliation(s)
- Liwen Yang
- Key Laboratory of Photobiology, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Shuangrong Liu
- Key Laboratory of Photobiology, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Rongcheng Lin
- Key Laboratory of Photobiology, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- CAS Center for Excellence in Molecular Plant Sciences, the Chinese Academy of Sciences, Beijing, 100093, China
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7
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Luo D, Qu L, Zhong M, Li X, Wang H, Miao J, Liu X, Zhao X. Vascular plant one-zinc finger 1 (VOZ1) and VOZ2 negatively regulate phytochrome B-mediated seed germination in Arabidopsis. Biosci Biotechnol Biochem 2020; 84:1384-1393. [DOI: 10.1080/09168451.2020.1740971] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Abstract
Seed germination is regulated by light. Phytochromes (Phys) act as red and far-red light photoreceptors to mediate seed germination. However, the mechanism of this process is not well understood. In this study, we found that the Arabidopsis thaliana mutants vascular plant one-zinc finger 1 (voz1) and voz2 showed higher seed germination percentage than wild type when PhyB was inactivated by far-red light. In wild type, VOZ1 and VOZ2 expression were downregulated after seed imbibition, repressed by PhyB, and upregulated by Phytochrome-interacting factor 1 (PIF1), a key negative regulator of seed germination. Red light irradiation and the voz1voz2 mutation caused increased expression of Gibberellin 3-oxidase 1 (GA3ox1), a gibberellin (GA) biosynthetic gene. We also found that VOZ2 is bound directly to the promoter of GA3ox1 in vitro and in vivo. Our findings suggest that VOZs play a negative role in PhyB-mediated seed germination, possibly by directly regulating GA3ox1 expression.
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Affiliation(s)
- Dan Luo
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
- Shenzhen Institute, Hunan University, Shenzhen, China
| | - Lina Qu
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
- Shenzhen Institute, Hunan University, Shenzhen, China
| | - Ming Zhong
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
- Shenzhen Institute, Hunan University, Shenzhen, China
| | - Xinmei Li
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
- Shenzhen Institute, Hunan University, Shenzhen, China
| | - Han Wang
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
| | - Jiahui Miao
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
| | - Xuanming Liu
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
| | - Xiaoying Zhao
- College of Biology, Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, China
- Shenzhen Institute, Hunan University, Shenzhen, China
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8
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Phytochrome B and REVEILLE1/2-mediated signalling controls seed dormancy and germination in Arabidopsis. Nat Commun 2016; 7:12377. [PMID: 27506149 PMCID: PMC4987513 DOI: 10.1038/ncomms12377] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 06/27/2016] [Indexed: 12/12/2022] Open
Abstract
Seeds maintain a dormant state to withstand adverse conditions and germinate when conditions become favourable to give rise to a new generation of flowering plants. Seed dormancy and germination are tightly controlled by internal and external signals. Although phytochrome photoreceptors are proposed to regulate primary seed dormancy, the underlying molecular mechanism remains elusive. Here we show that the REVEILLE1 (RVE1) and RVE2 transcription factors promote primary seed dormancy and repress red/far-red-light-reversible germination downstream of phytochrome B (phyB) in Arabidopsis thaliana. RVE1 and RVE2 expression is downregulated after imbibition and by phyB. RVE1 directly binds to the promoter of GIBBERELLIN 3-OXIDASE 2, inhibits its transcription and thus suppresses the biosynthesis of bioactive gibberellins. In addition, DELAY OF GERMINATION 1 also acts downstream of phyB. This study identifies a signalling pathway that integrates environmental light input with internal factors to control both seed dormancy and germination.
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9
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Su L, Hou P, Song M, Zheng X, Guo L, Xiao Y, Yan L, Li W, Yang J. Synergistic and Antagonistic Action of Phytochrome (Phy) A and PhyB during Seedling De-Etiolation in Arabidopsis thaliana. Int J Mol Sci 2015; 16:12199-212. [PMID: 26030677 PMCID: PMC4490439 DOI: 10.3390/ijms160612199] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/13/2015] [Accepted: 05/15/2015] [Indexed: 11/16/2022] Open
Abstract
It has been reported that Arabidopsis phytochrome (phy) A and phyB are crucial photoreceptors that display synergistic and antagonistic action during seedling de-etiolation in multiple light signaling pathways. However, the functional relationship between phyA and phyB is not fully understood under different kinds of light and in response to different intensities of such light. In this work, we compared hypocotyl elongation of the phyA-211 phyB-9 double mutant with the wild type, the phyA-211 and phyB-9 single mutants under different intensities of far-red (FR), red (R), blue (B) and white (W) light. We confirmed that phyA and phyB synergistically promote seedling de-etiolation in B-, B plus R-, W- and high R-light conditions. The correlation of endogenous ELONGATED HYPOCOTYL 5 (HY5) protein levels with the trend of hypocotyl elongation of all lines indicate that both phyA and phyB promote seedling photomorphogenesis in a synergistic manner in high-irradiance white light. Gene expression analyses of RBCS members and HY5 suggest that phyB and phyA act antagonistically on seedling development under FR light.
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Affiliation(s)
- Liang Su
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Pei Hou
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Meifang Song
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
- Beijing Radiation Center, Beijing 100875, China.
| | - Xu Zheng
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lin Guo
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Yang Xiao
- Graduate School, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lei Yan
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Wanchen Li
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
| | - Jianping Yang
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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10
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Su L, Hou P, Song M, Zheng X, Guo L, Xiao Y, Yan L, Li W, Yang J. Synergistic and Antagonistic Action of Phytochrome (Phy) A and PhyB during Seedling De-Etiolation in Arabidopsis thaliana. Int J Mol Sci 2015. [PMID: 26030677 DOI: 10.3390/2fijms160612199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023] Open
Abstract
It has been reported that Arabidopsis phytochrome (phy) A and phyB are crucial photoreceptors that display synergistic and antagonistic action during seedling de-etiolation in multiple light signaling pathways. However, the functional relationship between phyA and phyB is not fully understood under different kinds of light and in response to different intensities of such light. In this work, we compared hypocotyl elongation of the phyA-211 phyB-9 double mutant with the wild type, the phyA-211 and phyB-9 single mutants under different intensities of far-red (FR), red (R), blue (B) and white (W) light. We confirmed that phyA and phyB synergistically promote seedling de-etiolation in B-, B plus R-, W- and high R-light conditions. The correlation of endogenous ELONGATED HYPOCOTYL 5 (HY5) protein levels with the trend of hypocotyl elongation of all lines indicate that both phyA and phyB promote seedling photomorphogenesis in a synergistic manner in high-irradiance white light. Gene expression analyses of RBCS members and HY5 suggest that phyB and phyA act antagonistically on seedling development under FR light.
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Affiliation(s)
- Liang Su
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Pei Hou
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Meifang Song
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
- Beijing Radiation Center, Beijing 100875, China.
| | - Xu Zheng
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lin Guo
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Yang Xiao
- Graduate School, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lei Yan
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Wanchen Li
- Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
| | - Jianping Yang
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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11
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Arabidopsis DET1 degrades HFR1 but stabilizes PIF1 to precisely regulate seed germination. Proc Natl Acad Sci U S A 2015; 112:3817-22. [PMID: 25775589 DOI: 10.1073/pnas.1502405112] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Seed is an essential propagation organ and a critical strategy adopted by terrestrial flowering plants to colonize the land. The ability of seeds to accurately respond to light is vital for plant survival. However, the underlying mechanism is largely unknown. In this study, we reveal a circuit of triple feed-forward loops adopted by Arabidopsis seeds to exclusively repress germination in dark conditions and precisely initiate germination under diverse light conditions. We identify that de-etiolated 1 (DET1), an evolutionarily conserved protein, is a central repressor of light-induced seed germination. Genetic analysis demonstrates that DET1 functions upstream of long hypocotyl in far-red 1 (HFR1) and phytochrome interacting factor 1 (PIF1), the key positive and negative transcription regulators in seed germination. We further find that DET1 and constitutive photomorphogenic 10 (COP10) target HFR1 for protein degradation by assembling a COP10-DET1-damaged DNA binding protein 1-cullin4 E3 ligase complex. Moreover, DET1 and COP10 directly interact with and promote the protein stability of PIF1. Computational modeling reveals that phytochrome B (phyB)-DET1-HFR1-PIF1 and phyB-DET1-Protease-PIF1 are new signaling pathways, independent of the previously identified phyB-PIF1 pathway, respectively mediating the rapid and time-lapse responses to light irradiation. The model-simulated results are highly consistent with their experimental validations, suggesting that our mathematical model captures the essence of Arabidopsis seed germination networks. Taken together, this study provides a comprehensive molecular framework for light-regulated seed germination, improving our understanding of how plants respond to changeable environments.
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12
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Arana MV, Sánchez-Lamas M, Strasser B, Ibarra SE, Cerdán PD, Botto JF, Sánchez RA. Functional diversity of phytochrome family in the control of light and gibberellin-mediated germination in Arabidopsis. PLANT, CELL & ENVIRONMENT 2014; 37:2014-23. [PMID: 24471455 DOI: 10.1111/pce.12286] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 12/19/2013] [Accepted: 12/27/2013] [Indexed: 05/22/2023]
Abstract
In several species, seed germination is regulated by light in a way that restricts seedling emergence to the environmental conditions that are likely to be favourable for the success of the new individual, and therefore, this behaviour is recognized to have adaptive value. The phytochromes are one of the most relevant photoreceptors involved in light perception by plants. We explored the redundancy and diversity functions of the phytochrome family in the control of seed responsiveness to light and gibberellins (GA) by using a set of phytochrome mutants of Arabidopsis. Our data show that, in addition to the well-known role of phyB in the promotion of germination in response to high red to far-red ratios (R/FR), phyE and phyD stimulate germination at very low R/FR ratios, probably by promoting the action of phyA. Further, we show that phyC regulates negatively the seed responsiveness to light, unravelling unexpected functions for phyC in seed germination. Finally, we find that seed responsiveness to GA is mainly controlled by phyB, with phyC, phyD and phyE having relevant roles when acting in a phyB-deficient background. Our results indicate that phytochromes have multiple and complex roles during germination depending on the active photoreceptor background.
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Affiliation(s)
- M V Arana
- Instituto Nacional de Tecnología Agropecuaria, EEA Bariloche and CONICET, San Carlos de Bariloche, Río Negro, R8403DVZ, Argentina
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13
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Wilson RL, Bakshi A, Binder BM. Loss of the ETR1 ethylene receptor reduces the inhibitory effect of far-red light and darkness on seed germination of Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2014; 5:433. [PMID: 25221561 PMCID: PMC4147998 DOI: 10.3389/fpls.2014.00433] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 08/13/2014] [Indexed: 05/18/2023]
Abstract
When exposed to far-red light followed by darkness, wild-type Arabidopsis thaliana seeds fail to germinate or germinate very poorly. We have previously shown that the ethylene receptor ETR1 (ETHYLENE RESPONSE1) inhibits and ETR2 stimulates seed germination of Arabidopsis during salt stress. This function of ETR1 requires the full-length receptor. These roles are independent of ethylene levels and sensitivity and are mainly mediated by a change in abscisic acid (ABA) sensitivity. In the current study we find that etr1-6 and etr1-7 loss-of-function mutant seeds germinate better than wild-type seeds after illumination with far-red light or when germinated in the dark indicating an inhibitory role for ETR1. Surprisingly, this function of ETR1 does not require the receiver domain. No differences between these mutants and wild-type are seen when germination proceeds after treatment with white, blue, green, or red light. Loss of any of the other four ethylene receptor isoforms has no measurable effect on germination after far-red light treatment. An analysis of the transcript abundance for genes encoding ABA and gibberellic acid (GA) metabolic enzymes indicates that etr1-6 mutants may produce more GA and less ABA than wild-type seeds after illumination with far-red light which correlates with the better germination of the mutants. Epistasis analysis suggests that ETR1 may genetically interact with the phytochromes (phy), PHYA and PHYB to control germination and growth. This study shows that of the five ethylene receptor isoforms in Arabidopsis, ETR1 has a unique role in modulating the effects of red and far-red light on plant growth and development.
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Affiliation(s)
| | | | - Brad M. Binder
- Department of Biochemistry, Cellular, and Molecular Biology, University of TennesseeKnoxville, TN, USA
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Gibbs DC, Donohue K. Gene duplication and the environmental regulation of physiology and development. Ecol Evol 2014; 4:2202-16. [PMID: 25360261 PMCID: PMC4201434 DOI: 10.1002/ece3.1099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 04/07/2014] [Indexed: 11/08/2022] Open
Abstract
When different life stages have different environmental tolerances, development needs to be regulated so that each life stage experiences environmental conditions that are suitable for it, if fitness is to be maintained. Restricting the timing of developmental transitions to occur under specific combinations of environmental conditions is therefore adaptively important. However, impeding development can itself incur demographic and fitness costs. How do organisms regulate development and physiological processes so that they occur under the broadest range of permissive conditions? Gene duplication offers one solution: Multiple genes contribute to the same downstream process, but do so under distinct combinations of environmental conditions. We present a simple model to examine how environmental sensitivities of genes and how gene duplication influence the distribution of environmental conditions under which an end process will proceed. The model shows that the duplication of genes that retain their downstream function but diverge in environmental sensitivities can allow an end process to proceed under more than one distinct combination of environmental conditions. The outcomes depend on how upstream genes regulate downstream components, which genes in the pathway have diversified in their sensitivities, and the structure of the pathway.
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Affiliation(s)
- David C Gibbs
- Department of Biology, Duke University Box 90338, Durham, North Carolina, 27708
| | - Kathleen Donohue
- Department of Biology, Duke University Box 90338, Durham, North Carolina, 27708
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15
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Donohue K. WHY ONTOGENY MATTERS DURING ADAPTATION: DEVELOPMENTAL NICHE CONSTRUCTION AND PLEIOTORPY ACROSS THE LIFE CYCLE INARABIDOPSIS THALIANA. Evolution 2013; 68:32-47. [DOI: 10.1111/evo.12284] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Accepted: 09/25/2013] [Indexed: 12/14/2022]
Affiliation(s)
- Kathleen Donohue
- Department of Biology; Duke University; Box 90338 Durham NC 27708
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16
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Genetic interactions between brassinosteroid-inactivating P450s and photomorphogenic photoreceptors in Arabidopsis thaliana. G3-GENES GENOMES GENETICS 2012; 2:1585-93. [PMID: 23275881 PMCID: PMC3516480 DOI: 10.1534/g3.112.004580] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 10/03/2012] [Indexed: 01/12/2023]
Abstract
Plants use light as a source of information via a suite of photomorphogenic photoreceptors to optimize growth in response to their light environment. Growth-promoting hormones such as brassinosteroids also can modulate many of these responses. BAS1 and SOB7 are brassinosteroid-catabolizing P450s in Arabidopsis thaliana that synergistically/redundantly modulate photomorphogenic traits such as flowering time. The role of BAS1 and SOB7 in photomorphogenesis has been investigated by studying null-mutant genetic interactions with the photoreceptors phyA, phyB, and cry1 with regard to seed germination and flowering time. The removal of BAS1 and/or SOB7 rescued the low germination rate of the phyA-211 phyB-9 double-null mutant. With regard to floral induction, bas1-2 and sob7-1 showed a complex set of genetic interactions with photoreceptor-null mutants. Histochemical analysis of transgenic plants harboring BAS1:BAS1-GUS and SOB7:SOB7-GUS translational fusions under the control of their endogenous promoters revealed overlapping and distinct expression patterns. BAS1’s expression in the shoot apex increases during the phase transition from short-to-long-day growth conditions and requires phyB in red light. In summary, BAS1 and SOB7 displayed both simple and complex genetic interactions with the phytochromes in a plant-stage specific manner.
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Lee KP, Piskurewicz U, Turečková V, Carat S, Chappuis R, Strnad M, Fankhauser C, Lopez-Molina L. Spatially and genetically distinct control of seed germination by phytochromes A and B. Genes Dev 2012; 26:1984-96. [PMID: 22948663 DOI: 10.1101/gad.194266.112] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Phytochromes phyB and phyA mediate a remarkable developmental switch whereby, early upon seed imbibition, canopy light prevents phyB-dependent germination, whereas later on, it stimulates phyA-dependent germination. Using a seed coat bedding assay where the growth of dissected embryos is monitored under the influence of dissected endosperm, allowing combinatorial use of mutant embryos and endosperm, we show that canopy light specifically inactivates phyB activity in the endosperm to override phyA-dependent signaling in the embryo. This interference involves abscisic acid (ABA) release from the endosperm and distinct spatial activities of phytochrome signaling components. Under the canopy, endospermic ABA opposes phyA signaling through the transcription factor (TF) ABI5, which shares with the TF PIF1 several target genes that negatively regulate germination in the embryo. ABI5 enhances the expression of phytochrome signaling genes PIF1, SOMNUS, GAI, and RGA, but also of ABA and gibberellic acid (GA) metabolic genes. Over time, weaker ABA-dependent responses eventually enable phyA-dependent germination, a distinct type of germination driven solely by embryonic growth.
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Affiliation(s)
- Keun Pyo Lee
- Département de Biologie Végétale, 30, quai Ernest-Ansermet-Sciences III, Université de Genève, 1211 Genève 4, Switzerland
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18
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Yang R, Nishiyama K, Kamiya A, Ukaji Y, Inomata K, Lamparter T. Assembly of synthetic locked phycocyanobilin derivatives with phytochrome in vitro and in vivo in Ceratodon purpureus and Arabidopsis. THE PLANT CELL 2012; 24:1936-1951. [PMID: 22582099 PMCID: PMC3442579 DOI: 10.1105/tpc.111.094656] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/22/2012] [Accepted: 04/19/2012] [Indexed: 05/31/2023]
Abstract
Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red light-absorbing form, Pr, and the far-red-light-absorbing form, Pfr. Here we performed in vitro and in vivo studies using locked phycocyanobilin derivatives, termed 15 Z anti phycocyanobilin (15ZaPCB) and 15 E anti PCB (15EaPCB). Recombinant bacterial and plant phytochromes incorporated either chromophore in a noncovalent or covalent manner. All adducts were photoinactive. The absorption spectra of the 15ZaPCB and 15EaPCB adducts were comparable with those of the Pr and Pfr form, respectively. Feeding of 15EaPCB, but not 15ZaPCB, to protonemal filaments of the moss Ceratodon purpureus resulted in increased chlorophyll accumulation, modulation of gravitropism, and induction of side branches in darkness. The effect of locked chromophores on phytochrome responses, such as induction of seed germination, inhibition of hypocotyl elongation, induction of cotyledon opening, randomization of gravitropism, and gene regulation, were investigated in wild-type Arabidopsis thaliana and the phytochrome-chromophore-deficient long hypocotyl mutant hy1. All phytochrome responses were induced in darkness by 15EaPCB, not only in the mutant but also in the wild type. These studies show that the 15Ea stereochemistry of the chromophore results in the formation of active Pfr-like phytochrome in the cell. Locked chromophores might be used to investigate phytochrome responses in many other organisms without the need to isolate mutants. The induction of phytochrome responses in the hy1 mutant by 15EaPCB were however less efficient than by red light irradiation given to biliverdin-rescued seeds or seedlings.
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Affiliation(s)
- Rui Yang
- Karlsruhe Institute of Technology, Botanical Institute I, D-76128 Karlsruhe, Germany
| | - Kaori Nishiyama
- Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Ayumi Kamiya
- Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Yutaka Ukaji
- Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Katsuhiko Inomata
- Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Tilman Lamparter
- Karlsruhe Institute of Technology, Botanical Institute I, D-76128 Karlsruhe, Germany
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19
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Kircher S, Terecskei K, Wolf I, Sipos M, Adam E. Phytochrome A-specific signaling in Arabidopsis thaliana. PLANT SIGNALING & BEHAVIOR 2011; 6:1714-1719. [PMID: 22067110 PMCID: PMC3329343 DOI: 10.4161/psb.6.11.17509] [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: 05/31/2023]
Abstract
Among the five phytochromes in Arabidopsis thaliana, phytochrome A (phyA) plays a major role in seedling de-etiolation. Until now more then ten positive and some negative components acting downstream of phyA have been identified. However, their site of action and hierarchical relationships are not completely understood yet.
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Affiliation(s)
- Stefan Kircher
- Institute of Botany, University of Freiburg; Freiburg, Germany
| | - Kata Terecskei
- Biological Research Centre, Institute of Plant Biology; Szeged, Hungary
| | - Iris Wolf
- Institute of Botany, University of Freiburg; Freiburg, Germany
| | - Mark Sipos
- Biological Research Centre, Institute of Plant Biology; Szeged, Hungary
| | - Eva Adam
- Biological Research Centre, Institute of Plant Biology; Szeged, Hungary
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20
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Wolf I, Kircher S, Fejes E, Kozma-Bognár L, Schäfer E, Nagy F, Ádám É. Light-regulated nuclear import and degradation of Arabidopsis phytochrome-A N-terminal fragments. PLANT & CELL PHYSIOLOGY 2011; 52:361-72. [PMID: 21169346 PMCID: PMC3037077 DOI: 10.1093/pcp/pcq194] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 12/09/2010] [Indexed: 05/20/2023]
Abstract
The photoreceptor phytochrome-A (phyA) regulates germination and seedling establishment by mediating very low fluence (VLFR) and far-red high irradiance (FR-HIR) responses in Arabidopsis thaliana. In darkness, phyA homodimers exist in the biologically inactive Pr form and are localized in the cytoplasm. Light induces formation of the biologically active Pfr form and subsequent rapid nuclear import. PhyA Pfr, in contrast to the Pr form, is labile and has a half-life of ∼30 min. We produced transgenic plants in a phyA-201 null background that express the PHYA-yellow fluorescent protein (YFP) or the PHYA686-YFP-dimerization domain (DD) and PHYA686-YFP-DD-nuclear localization signal (NLS) or PHYA686-YFP-DD-nuclear exclusion signal (NES) fusion proteins. The PHYA686-YFP fusion proteins contained the N-terminal domain of phyA (686 amino acid residues), a short DD and the YFP. Here we report that (i) PHYA686-YFP-DD fusion protein is imported into the nucleus in a light-dependent fashion; (ii) neither of the PHYA686 fusion proteins is functional in FR-HIR and nuclear VLFR; and (iii) the phyA-dependent, blue light-induced inhibition of hypocotyl growth is mediated by the PHYA686-YFP-DD-NES but not by the PHYA686-YFP-DD-NLS and PHYA686-YFP-DD fusion proteins. We demonstrate that (i) light induces degradation of all PHYA N-terminal-containing fusion proteins and (ii) these N-terminal domain-containing fusion proteins including the constitutively nuclear PHYA686-YFP-DD-NLS and predominantly cytoplasmic PHYA686-YFP-DD-NES degrade at comparable rates but markedly more slowly than PHYA-YFP, whereas (iii) light-induced degradation of the native phyA is faster compared with PHYA-YFP.
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Affiliation(s)
- Iris Wolf
- Institute of Botany, Biology II, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany
| | - Stefan Kircher
- Institute of Botany, Biology II, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany
| | - Erzsébet Fejes
- Plant Biology Institute, Biological Research Centre, Temesvari krt. 62, H-6726 Szeged, Hungary
| | - László Kozma-Bognár
- Plant Biology Institute, Biological Research Centre, Temesvari krt. 62, H-6726 Szeged, Hungary
| | - Eberhard Schäfer
- Institute of Botany, Biology II, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany
| | - Ferenc Nagy
- Plant Biology Institute, Biological Research Centre, Temesvari krt. 62, H-6726 Szeged, Hungary
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, UK
| | - Éva Ádám
- Plant Biology Institute, Biological Research Centre, Temesvari krt. 62, H-6726 Szeged, Hungary
- *Corresponding author: E-mail, ; Fax, +36-62-433-434
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21
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Khan S, Verma G, Sharma S. A novel Ca2+-activated protease from germinating Vigna radiata seeds and its role in storage protein mobilization. JOURNAL OF PLANT PHYSIOLOGY 2010; 167:855-861. [PMID: 20149479 DOI: 10.1016/j.jplph.2010.01.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 01/20/2010] [Accepted: 01/20/2010] [Indexed: 05/28/2023]
Abstract
Calcium (Ca(2+))-dependent/activated proteases make decisive cleavages in proteins, affecting their further degradation/activation. Few such Ca(2+)-dependent proteases have been reported from plants, and none during germination-related events. Seeds are woken up from their quiescent state upon imbibition of water. The subsequent process of germination is strongly influenced by hormones (mainly gibberellins) and light, with both resulting in change in intracellular Ca(2+). We have investigated the effect of Ca(2+) on protease activity in extracts prepared from dry Vigna radiata (L.) Wilczec seeds and cotyledons 4, 24, 48 and 72h post-imbibition. Ca(2+)-activated protease activity is present at a very low level in dry seeds, rises with imbibition and peaks 24h post-imbibition. Subsequently, the activity rapidly declines, even as total protease activity continues to rise. Calcium activation of proteolysis was reversed by ethylene diamine tetraacetic acid (EDTA), ethylene glycol-bis (2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), 1,10, phenanthroline, chlorpromazine and by beta-mercaptoethanol in a concentration-dependent manner. Protease activity was also inhibited by para chloro mercuribenzoate (pCMB) and l-trans-epoxysuccinyl-leucylamido(4-guanidino) butane (E 64), while phenyl methyl sulfonyl fluoride (PMSF) and pepstatin did not effect Ca(2+) activation. The protease could be separated from the calmodulin fraction by size-exclusion chromatography, while retaining its ability for Ca(2+) activation, excluding the possibility of activation through calmodulin-based pathways. The presence of a Ca(2+)-activated protease in the cotyledons suggests its role in a predetermined program of germination involving elevation of cytosolic Ca(2+) levels during germination. This protease could be an important enzyme interfacing cytoplasmic signaling events and initiation of storage protein mobilization during seed germination.
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Affiliation(s)
- Sadaf Khan
- Department of Biochemistry, Lucknow University, Lucknow 226007, India
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22
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Franklin KA, Quail PH. Phytochrome functions in Arabidopsis development. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:11-24. [PMID: 19815685 PMCID: PMC2800801 DOI: 10.1093/jxb/erp304] [Citation(s) in RCA: 507] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 09/15/2009] [Accepted: 09/16/2009] [Indexed: 05/17/2023]
Abstract
Light signals are fundamental to the growth and development of plants. Red and far-red light are sensed using the phytochrome family of plant photoreceptors. Individual phytochromes display both unique and overlapping roles throughout the life cycle of plants, regulating a range of developmental processes from seed germination to the timing of reproductive development. The evolution of multiple phytochrome photoreceptors has enhanced plant sensitivity to fluctuating light environments, diversifying phytochrome function, and facilitating conditional cross-talk with other signalling systems. The isolation of null mutants, deficient in all individual phytochromes, has greatly advanced understanding of phytochrome functions in the model species, Arabidopsis thaliana. The creation of mutants null for multiple phytochrome combinations has enabled the dissection of redundant interactions between family members, revealing novel regulatory roles for this important photoreceptor family. In this review, current knowledge of phytochrome functions in the light-regulated development of Arabidopsis is summarised.
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Affiliation(s)
- Keara A Franklin
- Department of Biology, University of Leicester, Leicester LE1 7RH, UK.
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23
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Abstract
Seed dormancy allows seeds to overcome periods that are unfavourable for seedling established and is therefore important for plant ecology and agriculture. Several processes are known to be involved in the induction of dormancy and in the switch from the dormant to the germinating state. The role of plant hormones, the different tissues and genes involved, including newly identified genes in dormancy and germination are described in this chapter, as well as the use transcriptome, proteome and metabolome analyses to study these mechanistically not well understood processes.
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Affiliation(s)
- Leónie Bentsink
- Department of Molecular Plant Physiology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Maarten Koornneef
- Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
- Laboratory of Genetics, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands
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24
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Samis KE, Heath KD, Stinchcombe JR. Discordant longitudinal clines in flowering time and phytochrome C in Arabidopsis thaliana. Evolution 2008; 62:2971-83. [PMID: 18752603 DOI: 10.1111/j.1558-5646.2008.00484.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Using seasonal cues to time reproduction appropriately is crucial for many organisms. Plants in particular often use photoperiod to signal the time to transition to flowering. Because seasonality varies latitudinally, adaptation to local climate is expected to result in corresponding clines in photoperiod-related traits. By experimentally manipulating photoperiod cues and measuring the flowering responses and photoperiod plasticity of 138 Eurasian accessions of Arabidopsis thaliana, we detected strong longitudinal but not latitudinal clines in flowering responses. The presence of longitudinal clines suggests that critical photoperiod cues vary among populations occurring at similar latitudes. Haplotypes at PHYC, a locus hypothesized to play a role in adaptation to light cues, were also longitudinally differentiated. Controlling for neutral population structure revealed that PHYC haplotype influenced flowering time; however, the distribution of PHYC haplotypes occurred in the opposite direction to the phenotypic cline, suggesting that loci other than PHYC are responsible for the longitudinal pattern in photoperiod response. Our results provide previously missing empirical support for the importance of PHYC in mediating photoperiod sensitivity in natural populations of A. thaliana. However, they also suggest that other loci and epistatic interactions likely play a role in the determination of flowering time and that the environmental factors influencing photoperiod in plants vary longitudinally as well as latitudinally.
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Affiliation(s)
- Karen E Samis
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.
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25
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Meng PH, Macquet A, Loudet O, Marion-Poll A, North HM. Analysis of natural allelic variation controlling Arabidopsis thaliana seed germinability in response to cold and dark: identification of three major quantitative trait loci. MOLECULAR PLANT 2008; 1:145-54. [PMID: 20031921 DOI: 10.1093/mp/ssm014] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Light and temperature are key external factors in the control of Arabidopsis thaliana seed germination and dormancy mechanisms. Perception and response to these stimuli have to ensure that seedling emergence and growth occur at the most advantageous time for correct establishment. Analysis of over 300 Arabidopsis accessions identified 14, from 12 different geographical locations, that were able to germinate to greater than 20% at 6 degrees C in the dark. This natural variation was exploited to identify genetic loci responsible for cold-tolerant, dark germination. A quantitative trait loci approach was used on recombinant inbred line progeny of a cross between Bay-0 and Shahdara. Six distinct quantitative trait loci were identified, three of which were major loci, each responsible for 17-25% of the phenotypic variability in this trait. Parental phenotypes indicated that the majority of the cold-tolerant, dark-germination characteristics are related to light responses. Validation of the three major loci using heterogeneous inbred families confirmed the feasibility of fine mapping and cloning the genes at the quantitative trait loci responsible for cold-tolerant, dark germination.
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Affiliation(s)
- Ping-Hong Meng
- Laboratoire de Biologie des Semences, UMR 204, INRA, AgroParisTech, Institut Jean-Pierre Bourgin, F-78026 Versailles Cedex, France
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26
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Donohue K, Heschel MS, Butler CM, Barua D, Sharrock RA, Whitelam GC, Chiang GCK. Diversification of phytochrome contributions to germination as a function of seed-maturation environment. THE NEW PHYTOLOGIST 2008; 177:367-379. [PMID: 18028293 DOI: 10.1111/j.1469-8137.2007.02281.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Environmental conditions during seed maturation influence germination, but the genetic basis of maternal environmental effects on germination is virtually unknown. Using single and multiple mutants of phytochromes, it is shown here that different phytochromes contributed to germination differently, depending on seed-maturation conditions. Arabidopsis thaliana wild-type seeds that were matured under cool temperatures were intensely dormant compared with seeds matured at warmer temperature, and this dormancy was broken only after warm seed-stratification followed by cold seed-stratification. The warm-cold stratification broke dormancy in fresh seeds but not in dry after-ripened seeds. Functional PHYB and PHYD were necessary to break cool-induced dormancy, which indicates a previously unknown and ecologically important function for PHYD. Disruption of PHYA in combination with PHYD (but not PHYB) restored germination to near wild-type levels, indicating that PHYA contributes to the maintenance of cool-induced dormancy on a phyD background. Effects of seed-maturation temperature were much stronger than effects of seed-maturation photoperiod. PHYB contributed to germination somewhat more strongly in seeds matured under short days, whereas PHYD contributed to germination somewhat more strongly in seeds matured under long days. The variable contributions of different phytochromes to germination as a function of seed-maturation conditions reveal further functional diversification of the phytochromes during the process of germination. This study identifies among the first genes to be associated with maternal environmental effects on germination.
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Affiliation(s)
- Kathleen Donohue
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA
| | - M Shane Heschel
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA
| | - Colleen M Butler
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA
| | - Deepak Barua
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA
| | - Robert A Sharrock
- Department of Plant Sciences and Plant Pathology, Montana State University, PO Box 173150, Bozeman, MT 59717-3150, USA
| | - Garry C Whitelam
- Institute of Genetics, Adrian Building, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - George C K Chiang
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA
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27
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Kneissl J, Shinomura T, Furuya M, Bolle C. A rice phytochrome A in Arabidopsis: The Role of the N-terminus under red and far-red light. MOLECULAR PLANT 2008; 1:84-102. [PMID: 20031917 DOI: 10.1093/mp/ssm010] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The phytochrome (phy)A and phyB photoreceptors mediate three photobiological response modes in plants; whereas phyA can mediate the very-low-fluence response (VLFR), the high-irradiance response (HIR) and, to some extent, the low fluence response (LFR), phyB and other type II phytochromes only mediate the LFR. To investigate to what level a rice phyA can complement for Arabidopsis phyA or phyB function and to evaluate the role of the serine residues in the first 20 amino acids of the N-terminus of phyA, we examined VLFR, LFR, and HIR responses in phyB and phyAphyB mutant plants transformed with rice PHYA cDNA or a mutant rice PHYA cDNA in which the first 10 serine residues were mutated to alanines (phyA SA). Utilizing mutants without endogenous phyB allowed the evaluation of red-light-derived responses sensed by the rice phyA. In summary, the WT rice phyA could complement VLFR and LFR responses such as inhibition of hypocotyl elongation under pulses of FR or continuous R light, induction of flowering and leaf expansion, whereas the phyA SA was more specific for HIR responses (e.g. inhibition of hypocotyl elongation and anthocyanin accumulation under continuous far-red light). As the N-terminal serines can no longer be phosphorylated in the phyA SA mutant, this suggests a role for phosphorylation discriminating between the different phyA-dependent responses. The efficacy of the rice phyA expressed in Arabidopsis was dependent upon the developmental age of the plants analyzed and on the physiological response, suggesting a stage-dependent downstream modulation of phytochrome signaling.
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Affiliation(s)
- Julia Kneissl
- Ludwig-Maximilians-Universität München, Bereich Botanik, Menzinger Str. 67, 80638 München, Germany
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28
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Shen H, Luong P, Huq E. The F-box protein MAX2 functions as a positive regulator of photomorphogenesis in Arabidopsis. PLANT PHYSIOLOGY 2007; 145:1471-83. [PMID: 17951458 PMCID: PMC2151697 DOI: 10.1104/pp.107.107227] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 10/08/2007] [Indexed: 05/20/2023]
Abstract
Light is vital for plant growth and development. To respond to ambient light signals, plants are equipped with an array of photoreceptors, including phytochromes that sense red (R)/far-R (FR) regions and cryptochromes and phototropins that respond to the ultraviolet-A/blue (B) region of the light spectrum, respectively. Several positively and negatively acting components in light-signaling pathways have been identified using genetic approaches; however, the pathways are not saturated. Here, we characterize a new mutant named pleiotropic photosignaling (pps), isolated from a genetic screen under continuous R light. pps has longer hypocotyls and slightly smaller cotyledons under continuous R, FR, and B light compared to that of the wild type. pps is also hyposensitive to both R and FR light-induced seed germination. Although photosynthetic marker genes are constitutively expressed in pps in the dark at high levels, the expression of early light-regulated genes is reduced in the pps seedlings compared to wild-type seedlings under R light. PPS encodes MAX2/ORE9 (for MORE AXILLARY BRANCHES2/ORESARA9), an F-box protein involved in inflorescence architecture and senescence. MAX2 is expressed ubiquitously in the seedling stage. However, its expression is restricted to vascular tissues and meristems at adult stages. MAX2 is also localized to the nucleus. As an F-box protein, MAX2 is predicted to be a component of the SCF (for SKP, Cullin, and F-box protein) complex involved in regulated proteolysis. These results suggest that SCF(MAX2) plays critical roles in R, FR, and B light-signaling pathways. In addition, MAX2 might regulate multiple targets at different developmental stages to optimize plant growth and development.
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Affiliation(s)
- Hui Shen
- Section of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA
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Donohue K, Heschel MS, Chiang GCK, Butler CM, Barua D. Phytochrome mediates germination responses to multiple seasonal cues. PLANT, CELL & ENVIRONMENT 2007; 30:202-12. [PMID: 17238911 DOI: 10.1111/j.1365-3040.2006.01619.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We identified a new role of phytochrome in mediating germination responses to seasonal cues and thereby identified for the first time a gene involved in maternal environmental effects on germination. We examined the germination responses of a mutant, hy2-1, which is deficient in the phytochrome chromophore. The background genotype, Landsberg erecta (Ler), lacked dormancy in most treatments, while hy2-1 required cold stratification for germination in a manner that resembled a more dormant ecotype, Columbia (Col). Unlike Col, hy2-1 was not induced into dormancy by warm stratification. Therefore, the down-regulation of phytochrome-mediated germination pathways results in sensitivity to cold, but we found no evidence that reduced phytochrome activity enables the warm-induction of dormancy. Cool temperatures during seed maturation induced dormancy. The hy2-1 mutants did not overcome this dormancy, indicating that phytochrome-mediated pathways are required to break cold-induced dormancy. Ler did not respond to post-stratification temperature, but hy2-1 did respond, suggesting phytochrome pathways are involved in germination responses to temperature. In summary, phytochromes mediate dormancy and germination responses to seasonal cues experienced both during seed maturation and after dispersal. Phytochromes therefore appear to be involved in mediating seasonal germination timing, a trait of great ecological importance and one that is under strong natural selection.
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Affiliation(s)
- Kathleen Donohue
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave. Cambridge, MA 02138, USA.
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Appenroth KJ, Lenk G, Goldau L, Sharma R. Tomato seed germination: regulation of different response modes by phytochrome B2 and phytochrome A. PLANT, CELL & ENVIRONMENT 2006; 29:701-9. [PMID: 17080619 DOI: 10.1111/j.1365-3040.2005.01455.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Lycopersicon esculentum seeds germinate after rehydration in complete darkness. This response was inhibited by a far-red light (FR) pulse, and the inhibition was reversed by a red light (R) pulse. Comparison of germination in phytochrome-deficient mutants (phyA, phyB1, phyB2, phyAB1, phyB1B2 and phyAB1B2) showed that phytochrome B2 (PhyB2) mediates both responses. The germination was inhibited by strong continuous R (38 micromol m(-2) s(-1)), whereas weak R (28 nmol m(-2) s(-1)) stimulated seed germination. Hourly applied R pulses of the same photon fluence partially replaced the effect of strong continuous R. This response was called 'antagonistic' because it counteracts the low fluence response (LFR) induced by a single R pulse. This antagonistic response might be an adaptation to a situation where the seeds sit on the soil surface in full sunlight (adverse for germination), while weak R might reflect that situation under a layer of soil. Unexpectedly, the effects of continuous R or repeated R pulses were mediated by phytochrome A (PhyA). We therefore suggest that low levels of PhyA in its FR-absorbing form (Pfr) cause inhibition of seed germination produced either by extended R irradiation (by degradation of PhyA-Pfr) or by extended FR irradiation [keeping a low Pfr/R-absorbing form (Pr) ratio].
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Affiliation(s)
- Klaus J Appenroth
- University of Jena, Institute of General Botany and Plant Physiology, Dornburger Str. 159, 07743 Jena, Germany.
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Oh E, Kim J, Park E, Kim JI, Kang C, Choi G. PIL5, a phytochrome-interacting basic helix-loop-helix protein, is a key negative regulator of seed germination in Arabidopsis thaliana. THE PLANT CELL 2004; 16:3045-58. [PMID: 15486102 PMCID: PMC527197 DOI: 10.1105/tpc.104.025163] [Citation(s) in RCA: 316] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Accepted: 09/02/2004] [Indexed: 05/18/2023]
Abstract
The first decision made by an angiosperm seed, whether to germinate or not, is based on integration of various environmental signals such as water and light. The phytochromes (Phys) act as red and far-red light (Pfr) photoreceptors to mediate light signaling through yet uncharacterized pathways. We report here that the PIF3-like 5 (PIL5) protein, a basic helix-loop-helix transcription factor, is a key negative regulator of phytochrome-mediated seed germination. PIL5 preferentially interacts with the Pfr forms of Phytochrome A (PhyA) and Phytochrome B (PhyB). Analyses of a pil5 mutant in conjunction with phyA and phyB mutants, a pif3 pil5 double mutant, and PIL5 overexpression lines indicate that PIL5 is a negative factor in Phy-mediated promotion of seed germination, inhibition of hypocotyl negative gravitropism, and inhibition of hypocotyl elongation. Our data identify PIL5 as the first Phy-interacting protein that regulates seed germination.
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Affiliation(s)
- Eunkyoo Oh
- Department of Biological Sciences, KAIST, Daejeon 305-701, Korea
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Abstract
As sessile organisms, plants have evolved a multitude of developmental responses to cope with the ever-changing environmental conditions that challenge the plant throughout its life cycle. Of the many environmental cues that regulate plant development, light is probably the most important. From determining the developmental pattern of the emerging seedling, to influencing the organization of organelles to best maximize energy available for photosynthesis, light has dramatic effects on development during all stages of plant life. In plants, three classes of photoreceptors that mediate light perception have been characterized at the molecular level. The phytochromes recognize light in the red portion of the spectrum, while cryptochromes and phototropins perceive blue and UVA light. In this review, we discuss the different aspects of development that are regulated by these photoreceptors in the model plant species Arabidopsis thaliana and how the phytochromes, cryptochromes, and phototropins bring about changes in development seen in the growing plant.
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Affiliation(s)
- James A Sullivan
- Department of Molecular, Cellular, and Developmental Biology, Yale University, 165 Prospect Street, New Haven, CT 06520-8104, USA
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Kircher S, Gil P, Kozma-Bognár L, Fejes E, Speth V, Husselstein-Muller T, Bauer D, Adám E, Schäfer E, Nagy F. Nucleocytoplasmic partitioning of the plant photoreceptors phytochrome A, B, C, D, and E is regulated differentially by light and exhibits a diurnal rhythm. THE PLANT CELL 2002; 14:1541-55. [PMID: 12119373 PMCID: PMC150705 DOI: 10.1105/tpc.001156] [Citation(s) in RCA: 231] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2001] [Accepted: 04/03/2002] [Indexed: 05/18/2023]
Abstract
The phytochrome family of plant photoreceptors has a central role in the adaptation of plant development to changes in ambient light conditions. The individual phytochrome species regulate different or partly overlapping physiological responses. We generated transgenic Arabidopsis plants expressing phytochrome A to E:green fluorescent protein (GFP) fusion proteins to assess the biological role of intracellular compartmentation of these photoreceptors in light-regulated signaling. We show that all phytochrome:GFP fusion proteins were imported into the nuclei. Translocation of these photoreceptors into the nuclei was regulated differentially by light. Light-induced accumulation of phytochrome species in the nuclei resulted in the formation of speckles. The appearance of these nuclear structures exhibited distinctly different kinetics, wavelengths, and fluence dependence and was regulated by a diurnal rhythm. Furthermore, we demonstrate that the import of mutant phytochrome B:GFP and phytochrome A:GFP fusion proteins, shown to be defective in signaling in vivo, is regulated by light but is not accompanied by the formation of speckles. These results suggest that (1) the differential regulation of the translocation of phytochrome A to E into nuclei plays a role in the specification of functions, and (2) the appearance of speckles is a functional feature of phytochrome-regulated signaling.
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Affiliation(s)
- Stefan Kircher
- Albert-Ludwigs-Universität Freiburg, Institut für Biologie II/Botanik, Schänzlestrasse 1, 79104 Freiburg, Germany
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Hennig L, Stoddart WM, Dieterle M, Whitelam GC, Schäfer E. Phytochrome E controls light-induced germination of Arabidopsis. PLANT PHYSIOLOGY 2002; 128:194-200. [PMID: 11788765 DOI: 10.1104/pp.010559] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Germination of Arabidopsis seeds is light dependent and under phytochrome control. Previously, phytochromes A and B and at least one additional, unspecified phytochrome were shown to be involved in this process. Here, we used a set of photoreceptor mutants to test whether phytochrome D and/or phytochrome E can control germination of Arabidopsis. The results show that only phytochromes B and E, but not phytochrome D, participate directly in red/far-red light (FR)-reversible germination. Unlike phytochromes B and D, phytochrome E did not inhibit phytochrome A-mediated germination. Surprisingly, phytochrome E was required for germination of Arabidopsis seeds in continuous FR. However, inhibition of hypocotyl elongation by FR, induction of cotyledon unfolding, and induction of agravitropic growth were not affected by loss of phytochrome E. Therefore, phytochrome E is not required per se for phytochrome A-mediated very low fluence responses and the high irradiance response. Immunoblotting revealed that the need of phytochrome E for germination in FR was not caused by altered phytochrome A levels. These results uncover a novel role of phytochrome E in plant development and demonstrate the considerable functional diversification of the closely related phytochromes B, D, and E.
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Affiliation(s)
- Lars Hennig
- Department of Biology, Leicester University, Leicester LE1 7RH, United Kingdom
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Pepper AE, Seong-Kim M, Hebst SM, Ivey KN, Kwak SJ, Broyles DE. shl, a New set of Arabidopsis mutants with exaggerated developmental responses to available red, far-red, and blue light. PLANT PHYSIOLOGY 2001; 127:295-304. [PMID: 11553757 PMCID: PMC117985 DOI: 10.1104/pp.127.1.295] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2001] [Revised: 04/23/2001] [Accepted: 06/04/2001] [Indexed: 05/23/2023]
Abstract
The interaction of light perception with development is the subject of intensive genetic analysis in the model plant Arabidopsis. We performed genetic screens in low white light-a threshold condition in which photomorphogenetic signaling pathways are only partially active-for ethyl methane sulfonate-generated mutants with altered developmental phenotypes. Recessive mutants with exaggerated developmental responses were obtained in eight complementation groups designated shl for seedlings hyperresponsive to light. shl1, shl2, shl5, and shl3 shl4 (double mutant) seedlings showed limited or no phenotypic effects in darkness, but showed significantly enhanced inhibition of hypocotyl elongation in low-white, red, far-red, blue, and green light across a range of fluences. These results reflect developmental hyper-responsiveness to signals generated by both phytochrome and cryptochrome photoreceptors. The shl11 mutant retained significant phenotypic effects on hypocotyl length in both the phyA mutant and phyB mutant backgrounds but may be dependent on CRY1 for phenotypic expression in blue light. The shl2 phenotype was partially dependent on PHYB, PHYA, and CRY1 in red, far-red, and blue light, respectively. shl2 and, in particular, shl1 were partially dependent on HY5 activity for their light-hyperresponsive phenotypes. The SHL genes act (genetically) as light-dependent negative regulators of photomorphogenesis, possibly in a downstream signaling or developmental pathway that is shared by CRY1, PHYA, and PHYB and other photoreceptors (CRY2, PHYC, PHYD, and PHYE).
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Affiliation(s)
- A E Pepper
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA.
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Hennig L, Poppe C, Sweere U, Martin A, Schäfer E. Negative interference of endogenous phytochrome B with phytochrome A function in Arabidopsis. PLANT PHYSIOLOGY 2001; 125:1036-44. [PMID: 11161059 PMCID: PMC64903 DOI: 10.1104/pp.125.2.1036] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2000] [Revised: 10/05/2000] [Accepted: 11/09/2000] [Indexed: 05/18/2023]
Abstract
To study negative interactions between phytochromes, phytochrome B (phyB) overexpressor lines, the mutants phyA-201, phyB-4, phyB-5, phyD-1, phyA-201 phyB-5, phyA-201 phyD-1, and phyB-5 phyD-1 of Arabidopsis were used. Endogenous phyB, but not phytochrome D (phyD), partly suppressed phytochrome A (phyA)-dependent inhibition of hypocotyl elongation in far-red light (FR). Dichromatic irradiation demonstrated that the negative effect of phyB was largely independent of the photoequilibrium, i.e. far-red light absorbing form of phytochrome formation. Moreover, phyB-4, a mutant impaired in signal transduction, did not show a loss of inhibition of phyA by phyB. Overexpression of phyB, conversely, resulted in an enhanced inhibition of phyA function, even in the absence of supplementary carbohydrates. However, overexpression of a mutated phyB, which cannot incorporate the chromophore, had no detectable effect on phyA action. In addition to seedling growth, accumulation of anthocyanins in FR, another manifestation of the high irradiance response, was strongly influenced by phyB holoprotein. Induction of seed germination by FR, a very low fluence response, was suppressed by both endogenous phyB and phyD. In conclusion, we show that both classical response modes of phyA, high irradiance response, and very low fluence response are subject to an inhibitory action of phyB-like phytochromes. Possible mechanisms of the negative interference are discussed.
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Affiliation(s)
- L Hennig
- Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
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37
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Abstract
In the past few years great progress has been made in identifying and characterizing plant photoreceptors active in the blue/UV-A regions of the spectrum. These photoreceptors include cryptochrome 1 and cryptochrome 2, which are similar in structure and chromophore composition to the prokaryotic DNA photolyases. However, they have a C-terminal extension that is not present in photolyases and lack photolyase activity. They are involved in regulation of cell elongation and in many other processes, including interfacing with circadian rhythms and activating gene transcription. Animal cryptochromes that play a photoreceptor role in circadian rhythms have also been characterized. Phototropin, the protein product of the NPH1 gene in Arabidopsis, likely serves as the photoreceptor for phototropism and appears to have no other role. A plasma membrane protein, it serves as photoreceptor, kinase, and substrate for light-activated phosphorylation. The carotenoid zeaxanthin may serve as the chromophore for a photoreceptor involved in blue-light-activated stomatal opening. The properties of these photoreceptors and some of the downstream events they are known to activate are discussed.
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Affiliation(s)
- W R Briggs
- Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305, USA.
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Yamaguchi S, Smith MW, Brown RG, Kamiya Y, Sun T. Phytochrome regulation and differential expression of gibberellin 3beta-hydroxylase genes in germinating Arabidopsis seeds. THE PLANT CELL 1998; 10:2115-26. [PMID: 9836749 PMCID: PMC143973 DOI: 10.1105/tpc.10.12.2115] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Despite extensive studies on the roles of phytochrome in photostimulated seed germination, the mechanisms downstream of the photoreceptor that promote germination are largely unknown. Previous studies have indicated that light-induced germination of Arabidopsis seeds is mediated by the hormone gibberellin (GA). Using RNA gel blot analyses, we studied the regulation of two Arabidopsis genes, GA4 and GA4H (for GA4 homolog), both of which encode GA 3beta-hydroxylases that catalyze the final biosynthetic step to produce bioactive GAs. The newly isolated GA4H gene was expressed predominantly during seed germination. We show that expression of both GA4 and GA4H genes in imbibed seeds was induced within 1 hr after a brief red (R) light treatment. In the phytochrome B-deficient phyB-1 mutant, GA4H expression was not induced by R light, but GA4 expression still was, indicating that R light-induced GA4 and GA4H expression is mediated by different phytochromes. In contrast to the GA4 gene, the GA4H gene was not regulated by the feedback inhibition mechanism in germinating seeds. Our data demonstrate that expression of GA 3beta-hydroxylase genes is elevated by R light, which may result in an increase in biosynthesis of active GAs to promote seed germination. Furthermore, our results suggest that each GA 3beta-hydroxylase gene plays a unique physiological role during light-induced seed germination.
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Affiliation(s)
- S Yamaguchi
- Frontier Research Program, Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan.
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Poppe C, Sweere U, Drumm-Herrel H, Schäfer E. The blue light receptor cryptochrome 1 can act independently of phytochrome A and B in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1998; 16:465-71. [PMID: 9881166 DOI: 10.1046/j.1365-313x.1998.00322.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Blue light responses in higher plants can be mediated not only by specific blue light receptors, but also by the red/far-red photoreversible phytochrome system. The question of interdependence between these photoreceptors has been debated over many years. The availability of Arabidopsis mutants for the blue light receptor CRY1 and for the two major phytochromes phyA and phyB allows a reinvestigation of this question. The analysis of photocontrol of seed germination, inhibition of hypocotyl growth and anthocyanin accumulation clearly demonstrates that (i) phyA shows a strong control in blue light responses especially at low fluence rates; (ii) phyB mediated induction reactions can be reversed by subsequent blue light irradiations; and (iii) CRY1 mediates blue light controlled inhibition of hypocotyl growth only at fluence rates higher than 5 mumol m-2s-1 and independently of phytochrome A and B.
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Affiliation(s)
- C Poppe
- Institut für Biologie II, Botany, University of Freiburg, Germany
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40
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Quail PH. The phytochrome family: dissection of functional roles and signalling pathways among family members. Philos Trans R Soc Lond B Biol Sci 1998; 353:1399-403. [PMID: 9800202 PMCID: PMC1692352 DOI: 10.1098/rstb.1998.0294] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
There is considerable evidence that individual members of the five-membered phytochrome family of photoreceptors in Arabidopsis have differential functional roles in controlling plant photomorphogenesis. Emerging genetic evidence suggests that this differential activity may involve initially separate signalling pathway branches specific to individual family members.
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Affiliation(s)
- P H Quail
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA
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Whitelam GC, Patel S, Devlin PF. Phytochromes and photomorphogenesis in Arabidopsis. Philos Trans R Soc Lond B Biol Sci 1998; 353:1445-53. [PMID: 9800208 PMCID: PMC1692349 DOI: 10.1098/rstb.1998.0300] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Plants have evolved exquisite sensory systems for monitoring their light environment. The intensity, quality, direction and duration of light are continuously monitored by the plant and the information gained is used to modulate all aspects of plant development. Several classes of distinct photoreceptors, sensitive to different regions of the light spectrum, mediate the developmental responses of plants to light signals. The red-far-red light-absorbing, reversibly photochromic phytochromes are perhaps the best characterized of these. Higher plants possess a family of phytochromes, the apoproteins of which are encoded by a small, divergent gene family. Arabidopsis has five apophytochrome-encoding genes, PHYA-PHYE. Different phytochromes have discrete biochemical and physiological properties, are differentially expressed and are involved in the perception of different light signals. Photoreceptor and signal transduction mutants of Arabidopsis are proving to be valuable tools in the molecular dissection of photomorphogenesis. Mutants deficient in four of the five phytochromes have now been isolated. Their analysis indicates considerable overlap in the physiological functions of different phytochromes. In addition, mutants defining components acting downstream of the phytochromes have provided evidence that different members of the family use different signalling pathways.
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Casal JJ, Mazzella MA. Conditional synergism between cryptochrome 1 and phytochrome B is shown by the analysis of phyA, phyB, and hy4 simple, double, and triple mutants in Arabidopsis. PLANT PHYSIOLOGY 1998; 118:19-25. [PMID: 9733522 PMCID: PMC34855 DOI: 10.1104/pp.118.1.19] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/1998] [Accepted: 06/03/1998] [Indexed: 05/19/2023]
Abstract
Wild-type or phyA, phyB, or hy4 mutant Arabidopsis seedlings lacking phytochrome A (phyA), phytochrome B (phyB), or cryptochrome 1 (cry1), respectively, and the double and triple mutants were used in combination with blue-light treatments given simultaneously with red or far-red light. We investigated the interaction between phytochromes and cry1 in the control of hypocotyl growth and cotyledon unfolding. Under conditions deficient for cry1 (short exposures to blue light) or phyB (far-red background), these photoreceptors acted synergistically: Under short exposures to blue light (3 h/d) added to a red-light background, cry1 activity required phyB (e.g. the hy4 mutant was taller than the wild type but the phyBhy4 mutant was not taller than the phyB mutant). Under prolonged exposures to blue light (24 h/d) added to a far-red light background, phyB activity required cry1 (e.g. the phyAphyB mutant was taller than the phyA mutant but the phyAphyBhy4 mutant was not taller than the phyAhy4 mutant). Under more favorable light inputs, i.e. prolonged exposures to blue light added to a red-light background, the effects of cry1 and phyB were independent. Thus, the synergism between phyB and cry1 is conditional. The effect of cry1 was not reduced by the phyA mutation under any tested light condition. Under continuous blue light the triple mutant phyAphyBhy4 showed reduced hypocotyl growth inhibition and cotyledon unfolding compared with the phyAphyB mutant. The action of cry1 in the phyAphyB double mutant was higher under the red-light than the far-red-light background, indicating a synergistic interaction between cry1 and phytochromes C, D, or E; however, a residual action of cry1 independent of any phytochrome is likely to occur.
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Affiliation(s)
- J J Casal
- Departamento de Ecología, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, 1417-Buenos Aires, Argentina.
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