Two Distinct Molecular Types of Phytochrome A in Plants: Evidence of Existence and Implications for Functioning

Abstract

Phytochrome (phy) system in plants comprising a small number of phytochromes with phyA and phyB as major ones is responsible for acquiring light information in the red—far-red region of the solar spectrum. It provides optimal strategy of plant development under changing light conditions throughout all its life cycle beginning from seed germination and seedling establishment to fruiting and plant senescence. phyA was shown to participate in the regulation of all this cycle what is especially evident at its early stages. It mediates three modes of reactions—the very low and low fluence responses (VLFR and LFR) and the high irradiance responses (HIR). phyA is a sole light receptor in the far-red spectral region responsible for plant’s survival under dense plant canopy where light is enriched with the far-red component. Its appearance is believed to be one of the main factors of plants’ successful evolution. So far, it is widely accepted that one molecular phyA species is responsible for its complex functional manifestations. In this review, the evidence of the existence of two distinct phyA types—major, light-labile and soluble phyA′ and minor, relatively light-stable and amphiphilic phyA″—is presented what may account for the diverse modes of phyA action.

Functions of Phytochrome Interacting Factors (PIFs) in Adapting Plants to Biotic and Abiotic Stresses

“…Phytochromes (phys) are among these receptors that perceive red (R) and far-red light (FR) light signals with wavelengths ranging from 600 to 750 nm. In Arabidopsis, five phytochrome family members have been identified, ranging from phytochrome A-E (phyA-phyE) [4][5][6]. Phytochromes have an inactive form (Pr) for R light absorption and an activated form (Pfr) for FR light absorption [7,8].…”