Dawn and photoperiod sensing by phytochrome A

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 41; pp. 10523 - 10528
• Main Authors: Seaton, Daniel D., Toledo-Ortiz, Gabriela, Ganpudi, Ashwin, Kubota, Akane, Imaizumi, Takato, Halliday, Karen J.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.10.2018
• Subjects: Anthocyanins - metabolism; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biological Sciences; Biology; Circadian Rhythm; Circadian rhythms; Detection; Flowers & plants; Gene expression; Gene Expression Regulation, Plant; Genomics; Light; Photoperiod; Photoperiods; Phytochrome A; Phytochrome A - genetics; Phytochrome A - metabolism; Plants, Genetically Modified - genetics; Plants, Genetically Modified - growth & development; Plants, Genetically Modified - metabolism; Proteins; Receptors; Transcription factors; systems biology; photoperiodism; phytochrome; circadian rhythms; Arabidopsis
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1803398115

In plants, light receptors play a pivotal role in photoperiod sensing, enabling them to track seasonal progression. Photoperiod sensing arises from an interaction between the plant’s endogenous circadian oscillator and external light cues. Here, we characterize the role of phytochrome A (phyA) in photoperiod sensing. Our metaanalysis of functional genomic datasets identified phyA as a principal regulator of morning-activated genes, specifically in short photoperiods. We demonstrate that PHYA expression is under the direct control of the PHYTOCHROME INTERACTING FACTOR transcription factors, PIF4 and PIF5. As a result, phyA protein accumulates during the night, especially in short photoperiods. At dawn, phyA activation by light results in a burst of gene expression, with consequences for physiological processes such as anthocyanin accumulation. The combination of complex regulation of PHYA transcript and the unique molecular properties of phyA protein make this pathway a sensitive detector of both dawn and photoperiod.