Abstract
The molecular mechanism of light signal perception was analyzed using stem sections of etiolated rice (Oryza sativa L.) seedings irradiated with red light from a fluorescent lamp. The membrane and cytosol fractions were labeled by 40 nM [γ-32P]ATP for 10s at 0°C and proteins were separated by two-dimensional polyacrylamide gel electrophoresis. Phosphorylation of three proteins with molecular weights of 16, 17 and 18 kDa in the rice increased with the intensity of red light irradiation (50 μmol/m2/s) for 16 min. Most of the phosphorylation activity was present in the cytosol fraction. The three proteins cross-reacted with the anti-mucleoside diphosphate (NDP) kinase antibody. Phosphorylation of these proteins was correlated with changes in the activity of NDP kinase. These proteins phosphorylated histone III-S, a substurate for measuring the protein kinase activity. By phospho-amino acid analysis, phosphoserine was found present in the phosphorylated proteins. These rapidly phosphorylated proteins would thus appear to have the features of NDP kinase.
