phyAphyE

phyAphyE is a term used to describe the coordinated signaling output of the phyA and phyE phytochrome photoreceptors in plants, particularly in Arabidopsis thaliana. It is not a standalone gene but a conceptual representation of their combined effects on development and light responses.

Phytochromes are red/far-red photoreceptors that exist in two interconvertible forms, Pr and Pfr. Upon light, phyA and phyE switch to the Pfr form and initiate signaling, which regulates seed germination, seedling photomorphogenesis, and mature plant responses. phyA is especially important under very low light or continuous far-red, while phyE contributes to red/far-red light responses and can influence shade avoidance and timing of germination.

Mechanistically, activated phyA and phyE modulate transcription factors such as PIFs and HY5, leading to changes in gene expression. They can form nuclear localized signaling complexes and influence regulatory networks; phyA often drives rapid, light-labile responses, whereas phyE contributes to more persistent or context-dependent signaling.

Genetic studies in Arabidopsis suggest partially overlapping roles for phyA and phyE, with double mutants displaying stronger phenotypes under certain light conditions. The term phyAphyE is used to discuss their combined or redundant effects, rather than a single molecular entity.

Understanding phyAphyE helps describe how plants integrate light quality signals to optimize growth, flowering time, and germination. The concept remains a shorthand for receptor collaboration, and researchers continue to distinguish the specific contributions and regulatory networks of phyA and phyE.