The Influence of Anaerobiosis on Membrane-Associated Rice (O. sativa L.) Protein Kinase activities

Root and coleoptile membrane extracts of rice seedlings that were incubated aerobically or shifted to anoxia for 2 hours were compared for their endogenous protein kinase activities with the use of in vitro assays. The anoxic extracts showed a decreased labelling of a polypeptide of 73 kDa. This reduction was more evident in roots than in coleoptiles. The pattern of in vitro phosphorylated proteins obtained from membranes of rice coleoptiles cut from 8-day-old seedlings directly germinated in anaerobiosis was also analyzed. Differences with the pattern obtained from segments incubated anaerobically for 2 h were observed. Previously described rice calcium-dependent protein kinase activities are present in membrane preparations obtained from anaerobically treated roots and coleoptiles. Calcium-dependent phosphorylation of substrates like H1 histone (type III-S) and MARCKS peptide is shown. The rice CDPK activity capable of phosphorylating the MARCKS peptide is two-fold higher in coleoptile membrane preparations than roots.