title: Repression of shade-avoidance reactions by sunfleck induction of HY5 expression in Arabidopsis.
abstract: The light environment provides signals that play a critical role in the control of stem growth in plants. The reduced irradiance and altered spectral composition of shade light promote stem growth compared with unfiltered sunlight. However, whereas most studies have used seedlings exposed to contrasting but constant light treatments, the natural light environment may exhibit strong fluctuations. As a result of gaps in the canopy, plants shaded by neighbours may experience sunflecks, i.e., brief periods of exposure to unfiltered sunlight. Here, we show that sunflecks are perceived by phytochromes A and B, and inhibit hypocotyl growth in Arabidopsis thaliana mainly if they occur during the final portion of the photoperiod. By using forward and reverse genetic approaches we found that ELONGATED HYPOCOTYL 5, LATE ELONGATED HYPOCOTYL, PHYTOCHROME KINASE SUBSTRATE 4 and auxin signalling are key players in this response.
authors.affiliation: IFEVA, Facultad de Agronomía, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas, 1417 Buenos Aires, Argentina.
authors.forename: Romina
authors.initials: R
authors.lastname: Sellaro
authors.forename: Marcelo J
authors.initials: MJ
authors.lastname: Yanovsky
authors.forename: Jorge J
authors.initials: JJ
authors.lastname: Casal
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D057906:Circadian Clocks; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017440:Photoperiod; D051942:Phytochrome A / Q000235:genetics / Q000378:metabolism; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013472:Sunlight; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C109254:HY5 protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D012097:Repressor Proteins; D051939:Phytochrome B; C512593:PKS4 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases