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Fernández-Llamosas H, Ibero J, Thijs S, Imperato V, Vangronsveld J, Díaz E, Carmona M. Enhancing the Rice Seedlings Growth Promotion Abilities of Azoarcus sp. CIB by Heterologous Expression of ACC Deaminase to Improve Performance of Plants Exposed to Cadmium Stress. Microorganisms 2020; 8:E1453. [PMID: 32971998 PMCID: PMC7564240 DOI: 10.3390/microorganisms8091453] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 09/18/2020] [Accepted: 09/20/2020] [Indexed: 02/04/2023] Open
Abstract
Environmental pollutants can generate stress in plants causing increased ethylene production that leads to the inhibition of plant growth. Ethylene production by the stressed plant may be lowered by Plant Growth-Promoting Bacteria (PGPB) that metabolizes the immediate precursor of ethylene 1-aminocyclopropane-1-carboxylate (ACC). Thus, engineering PGPB with ACC deaminase activity can be a promising alternative to mitigate the harmful effects of pollutants and thus enhance plant production. Here we show that the aromatics-degrading and metal-resistant Azoarcus sp. CIB behaves as a PGP-bacterium when colonizing rice as an endophyte, showing a 30% increment in plant weight compared to non-inoculated plants. The cloning and expression of an acdS gene led to a recombinant strain, Azoarcus sp. CIB (pSEVA237acdS), possessing significant ACC deaminase activity (6716 nmol mg-1 h-1), constituting the first PGPB of the Rhodocyclaceae family equipped with this PGP trait. The recombinant CIB strain acquired the ability to protect inoculated rice plants from the stress induced by cadmium (Cd) exposure and to increase the Cd concentration in rice seedlings. The observed decrease of the levels of reactive oxygen species levels in rice roots confirms such a protective effect. The broad-host-range pSEVA237acdS plasmid paves the way to engineer PGPB with ACC deaminase activity to improve the growth of plants that might face stress conditions.
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Affiliation(s)
- Helga Fernández-Llamosas
- Microbial and Plant Biotechnology Department, Centro de Investigaciones Biológicas-CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain; (H.F.-L.); (J.I.); (E.D.)
| | - Juan Ibero
- Microbial and Plant Biotechnology Department, Centro de Investigaciones Biológicas-CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain; (H.F.-L.); (J.I.); (E.D.)
| | - Sofie Thijs
- Department of Environmental Biology, Centre for Environmental Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (S.T.); (V.I.); (J.V.)
| | - Valeria Imperato
- Department of Environmental Biology, Centre for Environmental Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (S.T.); (V.I.); (J.V.)
| | - Jaco Vangronsveld
- Department of Environmental Biology, Centre for Environmental Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (S.T.); (V.I.); (J.V.)
- Department of Plant Physiology, Faculty of Biology and Biotechnology, Maria Skłodowska-Curie University, 20-0033 Lublin, Poland
| | - Eduardo Díaz
- Microbial and Plant Biotechnology Department, Centro de Investigaciones Biológicas-CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain; (H.F.-L.); (J.I.); (E.D.)
| | - Manuel Carmona
- Microbial and Plant Biotechnology Department, Centro de Investigaciones Biológicas-CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain; (H.F.-L.); (J.I.); (E.D.)
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Seo DH, Yoon GM. Light-induced stabilization of ACS contributes to hypocotyl elongation during the dark-to-light transition in Arabidopsis seedlings. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 98:898-911. [PMID: 30776167 DOI: 10.1111/tpj.14289] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 02/07/2019] [Accepted: 02/11/2019] [Indexed: 05/25/2023]
Abstract
Hypocotyl growth during seedling emergence is a crucial developmental transition influenced by light and phytohormones such as ethylene. Ethylene and light antagonistically control hypocotyl growth in either continuous light or darkness. However, how ethylene and light regulate hypocotyl growth, including seedling emergence, during the dark-to-light transition remains elusive. Here, we show that ethylene and light cooperatively stimulate a transient increase in hypocotyl growth during the dark-to-light transition via the light-mediated stabilization of 1-aminocyclopropane-1-carboxylic acid (ACC) synthases (ACSs), the rate-limiting enzymes in ethylene biosynthesis. We found that, in contrast to the known inhibitory role of light in hypocotyl growth, light treatment transiently increases hypocotyl growth in wild-type etiolated seedlings. Moreover, ACC, the direct precursor of ethylene, accentuates the effects of light on hypocotyl elongation during the dark-to-light transition. We determined that light leads to the transient elongation of hypocotyls by stabilizing the ACS5 protein during the dark-to-light transition. Furthermore, biochemical analysis of an ACS5 mutant protein bearing an alteration in the C-terminus indicated that light stabilizes ACS5 by inhibiting the degradation mechanism that acts through the C-terminus of ACS5. Our study reveals that plants regulate hypocotyl elongation during seedling establishment by coordinating light-induced ethylene biosynthesis at the post-translational level. Moreover, the stimulatory role of light on hypocotyl growth during the dark-to-light transition provides additional insights into the known inhibitory role of light in hypocotyl development.
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Affiliation(s)
- Dong Hye Seo
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
- Purdue University Center for Plant Biology, Purdue University, West Lafayette, IN, 47907, USA
| | - Gyeong Mee Yoon
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
- Purdue University Center for Plant Biology, Purdue University, West Lafayette, IN, 47907, USA
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Bianchetti RE, Cruz AB, Oliveira BS, Demarco D, Purgatto E, Peres LEP, Rossi M, Freschi L. Phytochromobilin deficiency impairs sugar metabolism through the regulation of cytokinin and auxin signaling in tomato fruits. Sci Rep 2017; 7:7822. [PMID: 28798491 PMCID: PMC5552807 DOI: 10.1038/s41598-017-08448-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 07/10/2017] [Indexed: 12/22/2022] Open
Abstract
Phytochomes and plant hormones have been emerging as important regulators of fleshy fruit biology and quality traits; however, the relevance of phytochrome-hormonal signaling crosstalk in controlling fruit development and metabolism remains elusive. Here, we show that the deficiency in phytochrome chromophore phytochromobilin (PΦB) biosynthesis inhibits sugar accumulation in tomato (Solanum lycopersicum) fruits by transcriptionally downregulating sink- and starch biosynthesis-related enzymes, such as cell-wall invertases, sucrose transporters and ADP-glucose pyrophosphorylases. PΦB deficiency was also shown to repress fruit chloroplast biogenesis, which implicates more limited production of photoassimilates via fruit photosynthesis. Genetic and physiological data revealed the involvement of auxins and cytokinins in mediating the negative impact of PΦB deficiency on fruit sink strength and chloroplast formation. PΦB deficiency was shown to transcriptionally repress type-A TOMATO RESPONSE REGULATORs and AUXIN RESPONSE FACTORs both in pericarp and columella, suggesting active phytochrome-hormonal signaling crosstalk in these tissues. Data also revealed that PΦB deficiency influences fruit ripening by delaying the climacteric rise in ethylene production and signaling. Altogether, the data uncover the impact of phytochromobilin deficiency in fine-tuning sugar metabolism, chloroplast formation and the timing of fruit ripening and also reveal a link between auxins, cytokinins and phytochromes in regulating sugar import and accumulation in fruits.
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Affiliation(s)
- Ricardo Ernesto Bianchetti
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil
| | - Aline Bertinatto Cruz
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil
| | - Bruna Soares Oliveira
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil
| | - Diego Demarco
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil
| | - Eduardo Purgatto
- Departamento de Alimentos e Nutrição Experimental, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Professor Lineu Prestes, 580, 05508-000, São Paulo, Brazil
| | - Lázaro Eustáquio Pereira Peres
- Departamento de Ciências Biológicas, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Av. Pádua Dias, 11, CP 09, 13418-900, Piracicaba, Brazil
| | - Magdalena Rossi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil
| | - Luciano Freschi
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, 05508-900, São Paulo, Brazil.
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Zdarska M, Dobisová T, Gelová Z, Pernisová M, Dabravolski S, Hejátko J. Illuminating light, cytokinin, and ethylene signalling crosstalk in plant development. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4913-31. [PMID: 26022257 DOI: 10.1093/jxb/erv261] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Integrating important environmental signals with intrinsic developmental programmes is a crucial adaptive requirement for plant growth, survival, and reproduction. Key environmental cues include changes in several light variables, while important intrinsic (and highly interactive) regulators of many developmental processes include the phytohormones cytokinins (CKs) and ethylene. Here, we discuss the latest discoveries regarding the molecular mechanisms mediating CK/ethylene crosstalk at diverse levels of biosynthetic and metabolic pathways and their complex interactions with light. Furthermore, we summarize evidence indicating that multiple hormonal and light signals are integrated in the multistep phosphorelay (MSP) pathway, a backbone signalling pathway in plants. Inter alia, there are strong overlaps in subcellular localizations and functional similarities in components of these pathways, including receptors and various downstream agents. We highlight recent research demonstrating the importance of CK/ethylene/light crosstalk in selected aspects of plant development, particularly seed germination and early seedling development. The findings clearly demonstrate the crucial integration of plant responses to phytohormones and adaptive responses to environmental cues. Finally, we tentatively identify key future challenges to refine our understanding of the molecular mechanisms mediating crosstalk between light and hormonal signals, and their integration during plant life cycles.
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Affiliation(s)
- Marketa Zdarska
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Tereza Dobisová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Zuzana Gelová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Markéta Pernisová
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Siarhei Dabravolski
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Jan Hejátko
- Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
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Gupta SK, Sharma S, Santisree P, Kilambi HV, Appenroth K, Sreelakshmi Y, Sharma R. Complex and shifting interactions of phytochromes regulate fruit development in tomato. PLANT, CELL & ENVIRONMENT 2014; 37:1688-702. [PMID: 24433205 DOI: 10.1111/pce.12279] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 01/05/2014] [Indexed: 05/22/2023]
Abstract
Tomato fruit ripening is a complex metabolic process regulated by a genetical hierarchy. A subset of this process is also modulated by light signalling, as mutants encoding negative regulators of phytochrome signal transduction show higher accumulation of carotenoids. In tomato, phytochromes are encoded by a multi-gene family, namely PHYA, PHYB1, PHYB2, PHYE and PHYF; however, their contribution to fruit development and ripening has not been examined. Using single phytochrome mutants phyA, phyB1 and phyB2 and multiple mutants phyAB1, phyB1B2 and phyAB1B2, we compared the on-vine transitory phases of ripening until fruit abscission. The phyAB1B2 mutant showed accelerated transitions during ripening, with shortest time to fruit abscission. Comparison of transition intervals in mutants indicated a phase-specific influence of different phytochrome species either singly or in combination on the ripening process. Examination of off-vine ripened fruits indicated that ripening-specific carotenoid accumulation was not obligatorily dependent upon light and even dark-incubated fruits accumulated carotenoids. The accumulation of transcripts and carotenoids in off-vine and on-vine ripened mutant fruits indicated a complex and shifting phase-dependent modulation by phytochromes. Our results indicate that, in addition to regulating carotenoid levels in tomato fruits, phytochromes also regulate the time required for phase transitions during ripening.
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Affiliation(s)
- Suresh Kumar Gupta
- Repository of Tomato Genomics Resources, Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
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Becatti E, Petroni K, Giuntini D, Castagna A, Calvenzani V, Serra G, Mensuali-Sodi A, Tonelli C, Ranieri A. Solar UV-B radiation influences carotenoid accumulation of tomato fruit through both ethylene-dependent and -independent mechanisms. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2009; 57:10979-89. [PMID: 19877686 DOI: 10.1021/jf902555x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The effect of UV-B shielding on ethylene production in ripening tomato fruits and the contribution of ethylene and UV-B radiation on carotenoid accumulation and profile during ripening were assessed to get more insight about the interplay between these two regulatory factors. To this aim, rin and nor tomato mutants, unable to produce ripening ethylene, and cv Ailsa Craig were cultivated under control or UV-B depleted conditions until full fruit ripening. The significantly decreased ethylene evolution following UV-B depletion, evident only in Ailsa Craig, suggested the requirement of functional rin and nor genes for UVB-mediated ethylene production. Carotenoid content and profile were found to be controlled by both ethylene and UV-B radiation. This latter influenced carotenoid metabolism either in an ethylene-dependent or -independent way, as indicated by UVB-induced changes also in nor and rin carotenoid content and confirmed by correlation plots between ethylene evolution and carotenoid accumulation performed separately for control and UV-B shielded fruits. In conclusion, natural UV-B radiation influences carotenoid metabolism in a rather complex way, involving ethylene-dependent and -independent mechanisms, which seem to act in an antagonistic way.
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Affiliation(s)
- Elisa Becatti
- Department of Agricultural Chemistry and Biotechnology, University of Pisa, via del Borghetto 80, I-56124 Pisa
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Foo E, Ross JJ, Davies NW, Reid JB, Weller JL. A role for ethylene in the phytochrome-mediated control of vegetative development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 46:911-21. [PMID: 16805726 DOI: 10.1111/j.1365-313x.2006.02754.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Members of the phytochrome family of photoreceptors play key roles in vegetative plant development, including the regulation of stem elongation, leaf development and chlorophyll accumulation. Hormones have been implicated in the control of these processes in de-etiolating seedlings. However, the mechanisms by which the phytochromes regulate vegetative development in more mature plants are less well understood. Pea (Pisum sativum) mutant plants lacking phytochromes A and B, the two phytochromes present in this species, develop severe defects later in development, including short, thick, distorted internodes and reduced leaf expansion, chlorophyll content and CAB gene transcript level. Studies presented here indicate that many of these defects in phyA phyB mutant plants appear to be due to elevated ethylene production, and suggest that an important role of the phytochromes in pea is to restrict ethylene production to a level that does not inhibit vegetative growth. Mutant phyA phyB plants produce significantly more ethylene than WT plants, and application of an ethylene biosynthesis inhibitor rescued many aspects of the phyA phyB mutant phenotype. This deregulation of ethylene production in phy-deficient plants appears likely to be due, at least in part, to the elevated transcript levels of key ethylene-biosynthesis genes. The phytochrome A photoreceptor appears to play a prominent role in the regulation of ethylene production, as phyA, but not phyB, single-mutant plants also exhibit a phenotype consistent with elevated ethylene production. Potential interactions between ethylene and secondary plant hormones in the control of the phy-deficient mutant phenotype were explored, revealing that ethylene may inhibit stem elongation in part by reducing gibberellin levels.
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Affiliation(s)
- Eloise Foo
- School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tasmania 7001, Australia
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Pierik R, Cuppens MLC, Voesenek LACJ, Visser EJW. Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco. PLANT PHYSIOLOGY 2004; 136:2928-36. [PMID: 15448197 PMCID: PMC523355 DOI: 10.1104/pp.104.045120] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Revised: 06/09/2004] [Accepted: 07/06/2004] [Indexed: 05/18/2023]
Abstract
Plants respond to proximate neighbors with a suite of responses that comprise the shade avoidance syndrome. These phytochrome-mediated responses include hyponasty (i.e. a more vertical orientation of leaves) and enhanced stem and petiole elongation. We showed recently that ethylene-insensitive tobacco (Nicotiana tabacum) plants (Tetr) have reduced responses to neighbors, showing an important role for this gaseous plant hormone in shade avoidance. Here, we investigate interactions between phytochrome signaling and ethylene action in shade avoidance responses. Furthermore, we investigate if ethylene acts in these responses through an interaction with the GA class of hormones. Low red to far-red light ratios (R:FR) enhanced ethylene production in wild-type tobacco, resulting in shade avoidance responses, whereas ethylene-insensitive plants showed reduced shade avoidance responses. Plants with inhibited GA production showed hardly any shade avoidance responses at all to either a low R:FR or increased ethylene concentrations. Furthermore, low R:FR enhanced the responsiveness of hyponasty and stem elongation in both wild-type and Tetr plants to applied GA(3), with the stem elongation process being more responsive to GA(3) in the wild type than in Tetr. We conclude that phytochrome-mediated shade avoidance responses involve ethylene action, at least partly by modulating GA action.
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Affiliation(s)
- Ronald Pierik
- Department of Experimental Plant Ecology, Radboud University Nijmegen, Toernooiveld, 6525 ED Nijmegen, The Netherlands.
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Pierik R, Whitelam GC, Voesenek LACJ, de Kroon H, Visser EJW. Canopy studies on ethylene-insensitive tobacco identify ethylene as a novel element in blue light and plant-plant signalling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:310-9. [PMID: 15078333 DOI: 10.1111/j.1365-313x.2004.02044.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Plants growing at high densities express shade avoidance traits as a response to the presence of neighbours. Enhanced shoot elongation is one of the best researched shade avoidance components and increases light capture in dense stands. We show here that also leaf movements, leading to a more vertical leaf orientation (hyponasty), may be crucial in the early phase of competition. The initiation of shade avoidance responses is classically attributed to the action of phytochrome photoreceptors that sense red:far-red (R:FR) ratios in light reflected by neighbours, but also other signals may be involved. It was recently shown that ethylene-insensitive, transgenic (Tetr) tobacco plants, which are insensitive to the gaseous plant hormone ethylene, have reduced shade avoidance responses to neighbours. Here, we report that this is not related to a reduced response to low R:FR ratio, but that Tetr tobacco plants are unresponsive to a reduced photon fluence rate of blue light, which normally suppresses growth inhibition in wild-type (WT) plants. In addition to these light signals, ethylene levels in the canopy atmosphere increased to concentrations that could induce shade avoidance responses in WT plants. Together, these data show that neighbour detection signals other than the R:FR ratio are more important than previously anticipated and argue for a particularly important role for ethylene in determining plant responses to neighbours.
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Affiliation(s)
- Ronald Pierik
- Department of Experimental Plant Ecology, University of Nijmegen, Toernooiveld, 6525 ED Nijmegen, the Netherlands
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Finlayson SA, Lee IJ, Mullet JE, Morgan PW. The mechanism of rhythmic ethylene production in sorghum. The role of phytochrome B and simulated shading. PLANT PHYSIOLOGY 1999; 119:1083-9. [PMID: 10069847 PMCID: PMC32090 DOI: 10.1104/pp.119.3.1083] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/1998] [Accepted: 11/30/1998] [Indexed: 05/19/2023]
Abstract
Mutant sorghum (Sorghum bicolor [L.] Moench) deficient in functional phytochrome B exhibits reduced photoperiodic sensitivity and constitutively expresses a shade-avoidance phenotype. Under relatively bright, high red:far-red light, ethylene production by seedlings of wild-type and phytochrome B-mutant cultivars progresses through cycles in a circadian rhythm; however, the phytochrome B mutant produces ethylene peaks with approximately 10 times the amplitude of the wild type. Time-course northern blots show that the mutant's abundance of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase mRNA SbACO2 is cyclic and is commensurate with ethylene production, and that ACC oxidase activity follows the same pattern. Both SbACO2 abundance and ACC oxidase activity in the wild-type plant are very low under this regimen. ACC levels in the two cultivars did not demonstrate fluctuations coincident with the ethylene produced. Simulated shading caused the wild-type plant to mimic the phenotype of the mutant and to produce high amplitude rhythms of ethylene evolution. The circadian feature of the ethylene cycle is conditionally present in the mutant and absent in the wild-type plant under simulated shading. SbACO2 abundance in both cultivars demonstrates a high-amplitude diurnal cycle under these conditions; however, ACC oxidase activity, although elevated, does not exhibit a clear rhythm correlated with ethylene production. ACC levels in both cultivars show fluctuations corresponding to the ethylene rhythm previously observed. It appears that at least two separate mechanisms may be involved in generating high-amplitude ethylene rhythms in sorghum, one in response to the loss of phytochrome B function and another in response to shading.
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Affiliation(s)
- S A Finlayson
- Department of Soil and Crop Sciences, Texas A & M University, College Station, Texas 77843-2474, USA
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