THE INFLUENCE OF ANAEROBIOSIS ON MEMBRANE-ASSOCIATED RICE (ORYZA-SATIVA L) PROTEIN-KINASE ACTIVITIES

Root and coleoptile membrane extracts of rice seedlings that were incu bated aerobically or shifted to anoxia for 2 hours were compared for t heir endogenous protein kinase activities with the use of in vitro ass ays. The anoxic extracts showed a decreased labelling of a polypeptide of 73 kDa. This reduction was more evident in roots than in coleoptil es. The pattern of in vitro phosphorylated proteins obtained from memb ranes of rice coleoptiles cut from 8-day-old seedlings directly germin ated in anaerobiosis was also analyzed. Differences with the pattern o btained from segments incubated anaerobically for 2 h were observed. P reviously described rice calcium-dependent protein kinase activities a re present in membrane preparations obtained from anaerobically treate d roots and coleoptiles. Calcium-dependent phosphorylation of substrat es like H1 histone (type III-S) and MARCKS peptide is shown. The rice CDPK activity capable of phosphorylating the MARCKS peptide is two-fol d higher in coleoptile membrane preparations than roots.