Functional analysis of novel membrane receptors in Phytophthora

Phytophthora development and spore behaviour are influenced by many environmental components including temperature, humidity and plant secreted compounds. Extracellular signals are mainly transduced into cells via membrane receptors that activate downstream signalling pathways. Mining and comparative genomics of whole genome sequences revealed that Phytophthora harbours many novel enzymes with aberrant combinations of catalytic and regulatory domains. One group, that is well conserved among oomycetes, comprises GPCR-PIPKs, transmembrane proteins in which features of two super families are combined: G-protein coupled receptors (GPCRs) and phosphatidylinositol-phosphatekinases (PIPKs). This group of proteins potentially activates G protein and/or phospholipid mediated signal transduction pathways which might be involved in developmental or infection processes. We studied the expression of GPCR-PIPK genes and functionally analysed GPCR-PIPKs by gene-silencing or overexpression in Phytophthora. These membrane localized receptors are present in various cellular compartments rather than in the plasma membrane, as anticipated. Furthermore, this research revealed a vital role for GPCR-PIPKs in various stages of the Phytophthora life cycle. As such they are excellent and promising candidates for novel drug-targets.