The Late Endosomal HOPS Complex Anchors Active G-Protein Signaling Essential for Pathogenesis in Magnaporthe oryzae

Abstract

In Magnaporthe oryzae, the causal ascomycete of the devastating rice blast disease, the conidial germ tube tip must sense and respond to a wide array of requisite cues from the host in order to switch from polarized to isotropic growth, ultimately forming the dome-shaped infection cell known as the appressorium. Although the role for G-protein mediated Cyclic AMP signaling in appressorium formation was first identified almost two decades ago, little is known about the spatio-temporal dynamics of the cascade and how the signal is transmitted through the intracellular network during cell growth and morphogenesis. In this study, we demonstrate that the late endosomal compartments, comprising of a PI3P-rich (Phosphatidylinositol 3-phosphate) highly dynamic tubulo-vesicular network, scaffold active MagA/GαS, Rgs1 (a GAP for MagA), Adenylate cyclase and Pth11 (a non-canonical GPCR) in the likely absence of AKAP-like anchors during early pathogenic development in M. oryzae. Loss of HOPS component Vps39 and consequently the late endosomal function caused a disruption of adenylate cyclase localization, cAMP signaling and appressorium formation. Remarkably, exogenous cAMP rescued the appressorium formation defects associated with VPS39 deletion in M. oryzae. We propose that sequestration of key G-protein signaling components on dynamic late endosomes and/or endolysosomes, provides an effective molecular means to compartmentalize and control the spatio-temporal activation and rapid downregulation (likely via vacuolar degradation) of cAMP signaling amidst changing cellular geometry during pathogenic development in M. oryzae.

MoEnd3 regulates appressorium formation and virulence through mediating endocytosis in rice blast fungus Magnaporthe oryzae

“…The various signaling components then interact within the endosomal compartments for sustaining signaling [13]. Endosomal compartments contain early and late endosomes.…”

The endosomal recycling of FgSnc1 by FgSnx41–FgSnx4 heterodimer is essential for polarized growth and pathogenicity in Fusarium graminearum

“…In yeast, the localization of Snx41 to endosomes is dependent on phosphatidylinositol‐3‐kinase (PI3K) activity (Hettema et al ., ). To determine whether the association of FgSnx41 with the endosomal membrane also requires PI3K activity, we treated freshly harvested conidia with the PI3K‐specific inhibitor LY294002 (Ramanujam et al ., ), and found that FgSnx41‐GFP was neither in punctate form nor EE localized; rather, it appeared diffused in the cytosol, with very faint fluorescence (Fig. b).…”

The syntaxin protein (MoSyn8) mediates intracellular trafficking to regulate conidiogenesis and pathogenicity of rice blast fungus

“…In the incipient appressorium, some punctuate structures (GFP signal) were observed in the conidium, germ tube and appressoria. This localization pattern was the same as the G‐protein signaling mediated by regulator of G‐protein signalling‐1 ( Rgs1 ) in M. oryzae (Ramanujam et al ., ). In the mature appressorium, the GFP signal was mainly centralized in the form of large punctuate structures in the appressorium (Fig.…”