Journal Article

Circadian-Controlled Basic/Helix-Loop-Helix Factor, PIL6, Implicated in Light-Signal Transduction in <i>Arabidopsis thaliana</i>

Toru Fujimori, Takafumi Yamashino, Takahiko Kato and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 8, pages 1078-1086
Published in print August 2004 | ISSN: 0032-0781
Published online August 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch124
Circadian-Controlled Basic/Helix-Loop-Helix Factor, PIL6, Implicated in Light-Signal Transduction in Arabidopsis thaliana

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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.

Keywords: Keywords: Arabidopsis — Basic/helix-loop-helix factor — Circadian clock — Light-signal transduction.; Abbreviations: APRR, Arabidopsis pseudo response regulator; bHLH, basic/helix-loop-helix.

Journal Article.  6486 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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