LIGHT-INDUCED-CHANGES IN PHOSPHORYLATION STATUS OF LOW-MOLECULAR-WEIGHT WHEAT NUCLEAR PROTEINS

A large number of polypeptides were phosphorylated when in vitro prote in phosphorylation was carried out in nuclei isolated from dark-grown seedlings. For studying the effect of light, dark-grown seedlings were exposed to light and the isolated nuclear proteins phosphorylated in vitro. Although 4 h of white light was sufficient to alter the phospho rylation status of at least two polypeptides of 19 and 17 kD but the e ffect of light was more pronounced after irradiation for 8 h or more, leading to virtual disappearance of a 19 kD and emergence of a 17 kD p hosphopolypeptide. Studies using norflurazon, a bleaching herbicide, i ndicate that, in addition to 19 and 17 kD phosphopolypeptides, another 21 kD phosphopolypeptide may be involved in the de-etiolation process . However, the nature of the photoreceptor involved in these light-ind uced changes in nuclear protein phosphorylation remains to be establis hed.