Isolation and characterization of a cDNA coding cowpea (Vigna unguiculata (L) Walp.) calcineurin B-Iike protein-interacting protein kinase, VuCIPKJ

摘要

We isolated a calcineurin B-like protein (CBL)-interacting protein kinase (EC 2.7.11.1) homolog (VuCIPKT) from cowpea (Vigna unguiculata (L.) Walp.) with significant similarity to AtCIPKS (86% amino acid identity), which is involved in K~+ transport.VuCIPKl mKNA was detected in the whole plant by RT-PCR. Any significant change in VuCIPKl mRNA levels was not detected when cowpea was subjected to various environmental stresses. Immunoblot assay with an anti-VuCIPKl specific antibody and an anti-CBL antibody showed that immunologically CIPK- and CBL-related polypeptides were preferentially associated with membrane fractions of cowpea. The anti-VuCIPKl antibody cross-reacted to two different CIPK-related polypeptides with relative molecular masses of 51 kDa in root and 55kDa in mature leaf. Immunoprecipitation assay by anti-VuCIPKl antibody using cowpea leaf extracts showed that endogenous VuCIPKl was autophosphorylated on the threonine residues in response to salt stress. The recombinant VuCIPKl phosphorylated casein in the presence of Mn~(2+). These observations suggest that membrane-associated VuCIPKl is involved osmotic stress-activated kinase regulated by its phosphorylation status.