title: Circadian-controlled basic/helix-loop-helix factor, PIL6, implicated in light-signal transduction in Arabidopsis thaliana.
abstract: PHYTOCHROME-INTERACTING FACTOR-LIKE 6 (PIL6) is a member of the large family of basic/helix-loop-helix (bHLH) factors in Arabidopsis thaliana. This circadian-controlled transcription factor was previously suggested to interact with the clock component, TIMING OF CAB EXPRESSION 1 (TOC1). In this study, we isolated a loss-of-function mutant of PIL6, together with a transgenic line aberrantly expressing PIL6 in a manner independent of circadian rhythm. These mutant plants were simultaneously examined with special reference to circadian rhythm and light-signal transduction. The results suggested that PIL6 appears to be not directly involved in the clock function per se. However, the loss-of-function mutant (pil6-1) showed a remarkable phenotype in that it is hypersensitive to red light in seedling de-etiolation. This phenotype was similar to that observed for transgenic lines overexpressing TOC1 (or APRR1). Conversely, transgenic plants overexpressing PIL6 (PIL6-ox) are hyposensitive to red light under the same conditions. This phenotype was very similar to that observed for phyB mutants. The developmental morphologies of PIL6-ox, including the phenotype of early flowering, were also similar to those of phyB mutants. We propose that PIL6 acts as a negative regulator for a red light-mediated morphogenic response (e.g., elongation of hypocotyls in de-etiolation). Taken together, PIL6 might function at an interface between the circadian clock and red light-signal transduction pathways.
authors.affiliation: Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Fujimori
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yamashino
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuno
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins; D002940:Circadian Rhythm / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000528:radiation effects; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D018546:Hypocotyl / Q000235:genetics / Q000528:radiation effects; D008027:Light; D055537:Light Signal Transduction / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010775:Photic Stimulation; D030821:Plants, Genetically Modified / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C493633:PIL6 protein, Arabidopsis; C411822:TOC1 protein, Arabidopsis