抄録
Two cDNAs encoding phosphatidylinositol-specific phospholipase C, PpPLC1 and PpPLC2, were isolated from Physcomitrella patens. The N domain identified in Arabidopsis PI-PLCs as an EF hand-like domain was found in both isoforms, although that in PpPLC2 was a split type. PpPLC1 preferentially hydrolyzed phosphatidylinositol-4,5-bisphosphate at micromolar Ca2+ concentrations, while hydrolyzed phosphatidylinositol at millimolar Ca2+ concentration. Thus, PpPLC1 and PpPLC2 are typical and novel types of plant PI-PLC, respectively. Moreover, knock-out mutants of the PpPLC1 gene showed 1) an yellowish color by the reduction of chlorophyll contents, 2) an altered response to gravity, and 3) a reduction of cytokinin-induced gametophore formation. Since PpPLC1-GFP fusion protein localized at plasma membranes in protonemal tip cells, PpPLC1 is likely involved in the early stage of gravitropic response and cytokinin signaling. Our results imply new roles of plant PI-PLC in the regulation of chlorophyll contents, gravitropism and cytokinin-induced differentiation of gamethophore.
