MULTIPLE PHOTORECEPTORS MEDIATE THE LIGHT-INDUCED REDUCTION OF GUS-COP1 FROM ARABIDOPSIS HYPOCOTYL NUCLEI

The subcellular localization of COP1, a key photomorphogenic repressor , is regulated by light in Arabidopsis seedlings. Photoreceptor loss-o f-function mutants and dominant gain-of-function overexpression transg enes were both used to analyze the influences of the three photorecept ors, phyA, phyB, and CRY1, on the light-regulated subcellular localiza tion of COP1. Through a semiquantitative analysis of the nuclear abund ance of GUS-COP1 in the Various genetic backgrounds, the specific role s of the individual photoreceptors have been established. The data sug gest that multiple photoreceptors influence the light-regulated subcel lular localization of COP1 in white light. Under specific wavelengths of light, phyA, phyB, and CRY1 each play critical roles in mediating f ar-red, red, and blue light signals, respectively. Our data also suppo rt an interdependency between CRY1 and the phytochromes in mediating t he light-regulated subcellular localization of COP1 and thus seedling development.