Phytochrome‐hormonal signalling networks

Halliday, Karen; Fankhauser, Christian

doi:10.1046/j.1469-8137.2003.00689.x

Cited by 103 publications

(75 citation statements)

References 170 publications

(268 reference statements)

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“…Experimental evidence has indicated that classic plant growth hormones, including auxin, brassinosteriods, ethylene and gibberellic acid, are involved in light control of plant development. 2 Nonetheless, the role of ABA in light signaling is much less clear, although light affects the metabolism of ABA 3 and the expression of certain ABA-responsive genes. In a recent study, 4 we reported an interaction between the light signaling pathway and the ABA signaling pathway during seed germination and early seedling development.…”

Section: The Light-signaling Component Hy5 Mediates Aba Response In Smentioning

confidence: 99%

Role of HY5 in abscisic acid response in seeds and seedlings

Chen

Xiong

2008

Plant Signaling & Behavior

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response in late embryogenesis-abundant (LEA) gene expression, seed germination, seedling establishment and root growth; (2) HY5 mediates these ABA responses partly by regulating the transcription of the seed/seedling-specific ABA signaling regulator ABI5, (3) ABA specifically enhances HY5 binding to the ABI5 chromatin and; (4) ABI5 sensitizes light repression of hypocotyl elongation. These results raise interesting questions on the interaction of light signaling and ABA signaling and its potential significance in plant response to the environment. HY5 Controls the Expression of ABI5 and ABI5-Targeted GenesThe Arabidopsis HY5 is a positive regulator of seedling photomorphogenesis downstream of diverse photoreceptors. 5-7 HY5 encodes a transcription factor of the basic leucine zipper (bZIP) domain family and controls the expression of many light-responsive genes. The ABI5 locus also encodes a bZIP transcription factor whose accumulation inhibits seed germination and early seedling establishment. 8,9 ABI5 is expressed during seed maturation, seed germination and young seedling stages. Its expression pattern partly overlaps with that of HY5. Both HY5 protein and ABI5 protein are also subjected to proteolysis during the early seedling stage. These observations suggest that HY5 regulation of ABI5 may occur within a restricted developmental window and that there must be other factors controlling the activation of ABI5 by HY5. Indeed, in tobacco BY-2 protoplasts, we did not find clear activation of ABI5 promoter-driven reporter gene by HY5. This indicates that seed or early seedling-specific factors such as ABI3, LEC1 and FUS3 9-13 are also needed for ABI5 activation. Among others, ABI3 was previously suggested to act upstream of ABI5. 11,14 Nonetheless, in our yeast two-hybrid assays, HY5 did not physically interact with ABI3 (Chen H and Xiong L, unpublished), suggesting that these two components may not be in physical contact with one another if they are within a common ABI5 transcriptional activation complex. Further identification of the components in this complex will be important for revealing the signaling network controlling seed development and seed germination.Similar to ABI5, the downstream target genes of ABI5 may also be tightly regulated. Recent microarray experiments with the abi5 as well as hy5 mutants have identified genes potentially regulated by these transcription factors (reviewed in refs. 15 and 16). However, the low level of transcript abundance for some of these genes in seedlings and the sensitivity of their regulation to developmental stages and tissue types make it difficult to interpret some of the data obtained in these microarray assays. While the transcript levels for Light affects many aspects of plant development including seed germination, phototropism, de-etiolation and flowering. 1 Light regulates these processes at least partly through its regulation of the metabolism and signal transduction of phytohormones. Experimental evidence has indicated that classic plant growth hormones, in...

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Section: The Light-signaling Component Hy5 Mediates Aba Response In Smentioning

confidence: 99%

Role of HY5 in abscisic acid response in seeds and seedlings

Chen

Xiong

2008

Plant Signaling & Behavior

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“…There are several hormones (e.g., auxin, brassinosteroids, and gibberellins) involved in cell expansion that are interconnected with light signaling during photomorphogenesis (Halliday and Fankhauser, 2003;Neff et al, 2005). Multiple suppressors of the long-hypocotyl phenotype of phyB mutants have been identified, which are in involved both photomorphogenesis and hormone signaling (Reed et al, 1998;Neff et al, 1999).…”

Section: New Role For the Dof Transcription Factor Obp3 In Light Signmentioning

confidence: 99%

The Dof Transcription Factor OBP3 Modulates Phytochrome and Cryptochrome Signaling in Arabidopsis

et al. 2005

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Plants perceive subtle changes in light quality and quantity through a set of photoreceptors, including phytochromes and cryptochromes. Upon perception, these photoreceptors initiate signal transduction pathways leading to photomorphogenic changes in development. Using activation-tagging mutagenesis to identify novel light-signaling components, we have isolated a gain-of-function mutant, sob1-D (suppressor of phytochrome B-4 [phyB-4] dominant), which suppresses the long-hypocotyl phenotype of the phyB missense allele, phyB-4. The sob1-D mutant phenotype is caused by the overexpression of a Dof (DNA binding with one finger) transcription factor, OBF4 Binding Protein 3 (OBP3). A translational fusion between OBP3 and green fluorescent protein is nuclear localized in onion (Allium cepa) cells. Tissue-specific accumulation of an OBP3:OBP3-b-glucuronidase translational fusion is regulated by light in Arabidopsis thaliana. Hypocotyls of transgenic lines with reduced OBP3 expression are less responsive to red light. This aberrant phenotype in red light requires functional phyB, suggesting that OBP3 is a positive regulator of phyB-mediated inhibition of hypocotyl elongation. Furthermore, these partial-loss-of-function lines have larger cotyledons. This light-dependent cotyledon phenotype is most dramatic in blue light and requires functional cryptochrome 1 (cry1), indicating that OBP3 is a negative regulator of cry1-mediated cotyledon expansion. These results suggest a model where OBP3 is a component in both phyB and cry1 signaling pathways, acting as a positive and negative regulator, respectively. An alternate, though not mutually exclusive, model places OBP3 as a general inhibitor of tissue expansion with phyB and cry1, differentially modulating OBP3's role in this response.

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“…Blocking chloroplast development severely impairs light induction of transcription of nuclear genes that encode proteins targeted to the chloroplasts (Surpin et al, 2002). Light in turn affects the circadian clock (Devlin and Kay, 2000), the hormonal status (Halliday and Fankhauser, 2003) and the developmental status of the chloroplasts. Light also modulates the responses to hormones.…”

Section: Interaction Between Light and Other Signalsmentioning

confidence: 99%