Dawn and photoperiod sensing by phytochrome A ($) (PNAS)

Plants perceive the change of seasons based on measuring the duration of daylight. Flowering is a major seasonal response that depends on photoperiod. In this study, Seaton et al. looked at the role of phytochrome A (phyA) in photoperiod sensing. PHYA is the direct target of PIF4 and PIF5 transcription factors. PHYA transcript abundance is observed at night in short photoperiods, such as during the winter season. At dawn, phyA is activated and induces hundreds of downstream genes including genes in the anthocyanin biosynthesis pathway. Taken together, this work characterizes phyA as a sensor of dawn and short photoperiods. (Summary by Arif Ashraf)  PNAS: 10.1073/pnas.1803398115