Possible involvement of Ca2+-dependent protein kinases in spore germination of the fernOsmunda Japonica

Abstract

Fern gametophyte is a good model system to investigate signal transduction in plant cells. In this work, we examined whether CDPKs are involved in the mechanisms of spore germination of the fem Osmunda japonica. A protein extract from the spores included four CDPK isoforms with relative molecular weights of 5@ 53, 49, and 47 kDa, as detected by immunoblot analysis, and they showed CDPK-like activities, as detected by in-gel protein-kinase assay. It was also found that the inhibitors effective on CDPKs, such as a general protein kinase inhibitor, K252a, and a calmodulin antagonist, W-7, largely suppressed the spore germination, and that many proteins of the spores were phosphorylated in vivo in a calcium dependent manner in the period when the spores require external Ca 2 § for the germination. Furthermore, we showed that Sr z § and Mn 2 § which could substitute for Ca 2 § in the spore germination, were also able to activate the Osmuncla CDPKs. From these results, we concluded that CDPKs would participate in the spore germination of O. japonica.

Two novel protein kinase genes,OsMSRPK1 andOsMSURPK2, are regulated by diverse environmental stresses in rice

“…49, No. 3, 2006 In the case of plant Ca2 § protein kinases (CDPKs), which harbor a Ca2+-binding domain as well as a catalytic Ser/Thr kinase domain, Ca 2+ signals can be sensed and transmitted by a single protein (Sheen, 1996;Kamachi et al, 2004). Functional analyses of different plant CDPKs have provided evidence for the crucial roles these proteins play in divergent processes, e.g., hormonal and stress signaling, as well as in response to pathogens (Sheen, 1996).…”