The inositol polyphosphate phosphatase family in oomycetes

Phosphoinositides (PIs) play essential roles in intracellular transport and communication. They interact with a plethora of proteins, often modulating their activity. The level of individual PIs is governed by PI kinases [PI(P)Ks], and PI phosphatases (INPPs). Genome wide inventories in plant pathogenic Phytophthora spp. previously revealed that they encode an unique variety of PI(P)Ks. Among them GPCR-PIPKs (GKs), composed of a G-protein-coupled-receptor (GPCR) domain fused to a PIPK domain. So far nothing is known about PI(P)K counterparts in phosphoinositide signalling, the INPPs. We performed a genome-wide inventory for INPP genes in Phytophthora spp. and other oomycetes. Most genomes enclose around 22 INPPs genes in their genome, based on domain and motif conservation. Oomycete INPPs are well conserved in their catalytic domains and correlate to all known INPPs from other organisms. However, a subset of INPP are fusion products of INPP4 and INPP5 catalytic domains with an N-terminal GPCR moiety. This structure mimics that of GKs. As anticipated counterparts and the involvement of GKs in developmental transitions (Hua et al., 2013) this suggest that together these might determine specific spatiotemporal distribution of PIs. With the ongoing research on putative phospholipid based transport of proteins essential in pathogenicity processes it is worth to deduce their in vivo role. Also, with GPCRs as the main target of active agents, the GPCR-PI metabolizing enzymes might be valuable oomicide targets.