PHYC

PHYC, short for phytochrome C, is a member of the phytochrome family of photoreceptor proteins in plants. Phytochromes are red and far-red light sensors that regulate a broad range of developmental processes, including seed germination, seedling de-etiolation, shade avoidance, flowering time, and circadian rhythms. PHYC is one of several phytochrome genes found in many plants and is commonly discussed alongside PHYA, PHYB, PHYD, and PHYYE in Arabidopsis thaliana.

Structure and light sensing are typical of phytochromes: PHYC contains an N-terminal photosensory domain that binds a chromophore and a C-terminal regulatory domain. The proteins exist in two interconvertible forms, Pr (inactive) and Pfr (active). Upon absorbing red light, Pr converts to Pfr, enabling PHYC to influence gene expression and developmental programs. Light quality and quantity, as well as interactions with other phytochromes, shape PHYC’s activity.

Function and interactions are partly redundant with other phytochromes. In Arabidopsis and other species, PHYC contributes to responses to red and far-red light and can modulate germination, seedling growth, shade avoidance, and flowering time depending on the light environment. PHYC signaling engages with downstream transcription factors such as PIFs (phytochrome-interacting factors) and other components of the light signaling network, integrating light cues with the circadian clock and hormonal pathways.

PHYC homologs are widespread in land plants, making the gene a subject of interest for basic photomorphogenesis research and potential crop improvement strategies through manipulation of light responses.