%0 Journal Article
%T Phospholipase C¦Ä regulates germination of Dictyostelium spores
%A Peter Van Dijken
%A Peter JM Van Haastert
%J BMC Cell Biology
%D 2001
%I BioMed Central
%R 10.1186/1471-2121-2-25
%X Plc-null spores germinate at alkaline pH, reduced temperature or increased osmolarity, conditions at which the emerging amoebae can not grow. In contrast, food-activated wild-type spores return to dormancy till conditions in the environment allow growth. The analysis of inositol 1,4,5-trisphosphate (IP3) levels and the effect of added IP3 uncover an unexpected mechanism how PLC regulates spore germination: i) deletion of PLC induces the enhanced activity of an IP5 phosphatase leading to high IP3 levels in plc-null cells; ii) in wild-type spores unfavourable conditions inhibit PLC leading to a reduction of IP3 levels; addition of exogenous IP3 to wild-type spores induces germination at unfavourable conditions; iii) in plc-null spores IP3 levels remain high, also at unfavourable environmental conditions.The results imply that environmental conditions regulate PLC activity and that IP3 induces spore germination; the uncontrolled germination of plc-null spores is not due to a lack of PLC activity but to the constitutive activation of an alternative IP3-forming pathway.Many extracellular signals activate inositide-specific phospholipase C (PLC) thereby producing the second messengers Ins(1,4,5)P3 and diacylglycerol [1]. Three types of PLC are known, PLC-¦Â, PLC-¦Ã and PLC-¦Ä which are regulated by G-proteins, receptor tyrosine kinases, and Ca2+, respectively [2]. Animals such as human and rat, but also C. elegans, Artemia, Loligo forbesi and Drosophila possess all three PLC isoforms [3-6]. However, in non-animals exclusively PLC-¦Ä has been identified, e.g. in soybean [7] and catfish [8], and the lower eukaryotes Dictyostelium discoideum[9], Saccharomyces cerevisiae[10-12] and Schizosaccharomyces pombe[13]. This phylogenetic distribution of PLC isozymes is in accordance with the deduced three dimensional structure, suggesting that PLC-¦Ä is the ancient isoform to which specific domains were added in PLC-¦Â and PLC-¦Ã [14,15].Dictyostelium cells live in the soil where they feed
%U http://www.biomedcentral.com/1471-2121/2/25