OVEREXPRESSION OF RICE PHYTOCHROME A IN ARABIDOPSIS: DIVERSE ROLE IN MULTIPLE PHYSIOLOGICAL RESPONSES

Abstract

Phytochrome A predominantly mediates responses to prolonged far-red light such as the inhibition of hypocotyl elongation. It also acts in controlling responses to FR light pulses. To investigate to what extent rice phytochrome A complements the function of Arabidopsis phytochrome A, we examined hypocotyl elongation growth, seed germination, and greening in etiolated seedlings of phyA-211 mutant plants, WT and two kinds of transgenic plants in which WT and phyA211 mutants overexpressed rice PHYA cDNA. We found that ectopic expression of rice phytochrome A could partially rescue the sensitivity of phyA-211 mutant hypocotyls to prolonged far-red light and replace Arabidopsis phytochrome A in the promotion of seed germination and recovery of the ability to de-etiolate. Moreover, under end-of-day far-red light (EODFR), the exogenous rice phytochrome A was found to restore some aspects of growth in phyA-211 mutants, such as hypocotyl elongation, petiole elongation and flowering time. The diverse role of rice phytochrome A in the physiological responses of Arabidopsis implies the substitution of phytochrome signaling between monocots and dicots.