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Spatially and genetically distinct control of seed germination by phytochromes A and B

Turečková, Veronika
Carat, Solenne
Strnad, Miroslav
Fankhauser, Christian
Published in Genes and Development. 2012, vol. 26, no. 17, p. 1984-1996
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.
Keywords Abscisic Acid/metabolismArabidopsis/embryology/genetics/metabolismArabidopsis Proteins/metabolismEndosperm/metabolismGene Expression Regulation, PlantGerminationPhytochrome A/metabolismPhytochrome B/metabolismPlant Growth Regulators/metabolismPromoter Regions, GeneticSeeds/embryology/metabolismSignal Transduction
PMID: 22948663
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Research group Groupe Lopez-Molina
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LEE, Keun Pyo et al. Spatially and genetically distinct control of seed germination by phytochromes A and B. In: Genes and Development, 2012, vol. 26, n° 17, p. 1984-1996. https://archive-ouverte.unige.ch/unige:43509

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Deposited on : 2014-12-16

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