GK4, a G‐protein‐coupled receptor with a phosphatidylinositol phosphate kinase domain in Phytophthora infestans, is involved in sporangia development and virulence

Abstract

SummaryFor dispersal and host infection plant pathogens largely depend on asexual spores. Pathogenesis and sporulation are complex processes that are governed by cellular signalling networks including G-protein and phospholipid signalling. Oomycetes possess a family of novel proteins called GPCR-PIPKs (GKs) that are composed of a seven-transmembrane spanning (7-TM) domain fused to a phosphatidylinositol phosphate kinase (PIPK) domain. Based on this domain structure GKs are anticipated to link G-protein and phospholipid signal pathways; however, their functions are currently unknown. Expression analyses of the 12 GK genes in Phytophthora infestans and their orthologues in Phytophthora sojae, revealed differential expression during asexual development. PiGK1 and PiGK4 were fused to monomeric red fluorescent protein (mRFP) and ectopically expressed in P. infestans. In growing hyphae different subcellular distribution patterns were observed indicating that these two GKs act independently during development. We focused on the functional analyses of PiGK4. Its localization suggested involvement in cell differentiation and elongation and its 7-TM domain showed a canonical GPCR membrane topology. Silencing of GK4 and overexpression of full-length and truncated constructs in P. infestans revealed that PiGK4 is not only involved in spore germination and hyphal elongation but also in sporangia cleavage and infection.

The cell biology of late blight disease

“…Similarly, two oomycete-specific G protein coupled receptors with phosphatidylinositol phosphate kinase domains (called GK1 and GK4) were localised to vesicles in germinating P. infestans sporangia in vitro [18]. Although the two GKs are expressed throughout infection, and GK4 and G protein-mediated signalling are required for full pathogenicity [18, 19], the behaviour of GK1 and GK4 have yet to be investigated during infection.…”

“…Although the two GKs are expressed throughout infection, and GK4 and G protein-mediated signalling are required for full pathogenicity [18, 19], the behaviour of GK1 and GK4 have yet to be investigated during infection.…”

Profiling the Secretome and Extracellular Proteome of the Potato Late Blight Pathogen Phytophthora infestans

“…The mechanism that triggers protein secretion in Phytophthora remains to be determined but, as reported for fungi, nutrient sensing G protein-coupled receptors (GPCRs) could play a crucial role in this process (57). Indeed, the Phytophthora genomes harbor around 60 genes encoding putative GPCRs, among which are novel classes that might be involved in direct downstream signaling and play roles in chemotaxis as well as in developmental aspects (58,59).…”

Chemotaxis and oospore formation in Phytophthora sojae are controlled by G‐protein‐coupled receptors with a phosphatidylinositol phosphate kinase domain

“…Two of them, PsGK4 ( Ps129854 ) and PsGK5 ( Ps130286 ), with intermediate transcription levels were selected for further analysis. They are among the most conserved GK proteins in oomycetes (Hua et al ., , accompanying paper; Table S1) and it is therefore likely that the signalling pathways in which these GKs act, are also conserved. Real‐time quantitative PCR was employed to analyse the expression of PsGK4 and PsGK5 during asexual development and infection.…”