title: Transcriptional programs related to phytochrome A function in Arabidopsis seed germination.
abstract: In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B (phyB) and phytochrome A (phyA). Despite the abundant information concerning the molecular basis of phyB signaling downstream of PIF1/PIL5, the signaling network inducing germination by phyA is poorly known. Here, we describe the influence of phyA on the transcriptome of Arabidopsis seeds when germination is induced by a far-red (FR) pulse. The expression of 11% of the genome was significantly regulated by phyA. Most of the genes were up-regulated and the changes noted late (i.e. 5 h after a FR pulse), whereas changes in down-regulated genes were more abundant earlier (i.e. 0.5 h after a FR pulse). Auxin- and GA-associated elements were overrepresented in the genes that were modified by phyA. A significant number of genes whose expression was affected by phyA had not been previously reported to be dependent on PIL5. Among them, homozygotic mutant seeds of MYB66, a SAUR-like protein, PIN7, and GASA4 showed an impaired promotion of germination by phyA. Natural variation at the transcriptional level was found in early signaling and GA metabolic genes, but not in ABA metabolic and expansin genes between Columbia and Landsberg erecta accessions. Although phyA and phyB/PIL5 signaling pathways share some molecular components, our data suggest that phyA signaling is partially independent of PIL5 when germination is promoted by very low fluences of light.
authors.affiliation: IFEVA, Facultad de Agronomía, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas, Av. San Martín 4453, C1417DSE, Ciudad de Buenos Aires, Argentina.
authors.forename: Silvia E
authors.initials: SE
authors.lastname: Ibarra
authors.forename: Gabriela
authors.initials: G
authors.lastname: Auge
authors.forename: Rodolfo A
authors.initials: RA
authors.lastname: Sánchez
authors.forename: Javier F
authors.initials: JF
authors.lastname: Botto
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D018525:Germination; D005875:Gibberellins / Q000235:genetics; D009154:Mutation; D051942:Phytochrome A / Q000235:genetics / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000235:genetics; D012639:Seeds / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004269:DNA, Bacterial; D005875:Gibberellins; D051942:Phytochrome A; D010937:Plant Growth Regulators; D014157:Transcription Factors; C036483:T-DNA; C508068:At2g20180 protein, Arabidopsis
keywords: Arabidopsis seeds; PIF1/PIL5; germination; light; phytochrome A (phyA); phytochrome B (phyB); transcriptome