title: Sorting nexin Snx41 is essential for conidiation and mediates glutathione-based antioxidant defense during invasive growth in Magnaporthe oryzae.
abstract: The sorting nexins Atg20/Snx42 and Snx41 regulate membrane traffic and endosomal protein sorting and are essential for Cvt and/or pexophagy in yeast. Previously, we showed that macroautophagy is necessary for conidiation in the rice-blast fungus Magnaporthe oryzae. Here, we analyzed the physiological function(s) of selective autophagy in Magnaporthe through targeted deletion of MGG_12832, an ortholog of yeast SNX41 and ATG20/SNX42. Loss of MGG_12832 (hereafter SNX41) abolished conidia formation and pathogenesis in M. oryzae. Snx41-GFP localized as dynamic puncta or short tubules that are partially associated with autophagosomes and/or autophagic vacuoles. PX domain, but not macroautophagy per se, was required for such localization of Snx41-GFP in Magnaporthe. Although not required for nonselective autophagy, Snx41 was essential for pexophagy in Magnaporthe. We identified Oxp1, an ATP-dependent oxoprolinase in the gamma-glutamyl cycle, as a binding partner and potential retrieval target of Snx41-dependent protein sorting. The substrate of Oxp1, 5-oxoproline, could partially restore conidiation in the snx41Δ. Exogenous glutathione, a product of the gamma-glutamyl cycle, significantly restored pathogenicity in the snx41Δ mutant, likely through counteracting the oxidative stress imposed by the host. We propose that the gamma-glutamyl cycle and glutathione biosynthesis are subject to regulation by Snx41-dependent vesicular trafficking, and mediate antioxidant defense crucial for in planta growth and pathogenic differentiation of Magnaporthe at the onset of blast disease in rice.
authors.affiliation: Temasek Life Sciences Laboratory, and Department of Biological Sciences, 1 Research Link, National University of Singapore, Singapore.
authors.forename: Yi Zhen
authors.initials: YZ
authors.lastname: Deng
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Qu
authors.forename: Yunlong
authors.initials: Y
authors.lastname: He
authors.forename: Naweed I
authors.initials: NI
authors.lastname: Naqvi
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001343:Autophagy; D005656:Fungal Proteins / Q000378:metabolism*; D017353:Gene Deletion; D005978:Glutathione / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D001467:Hordeum / Q000166:cytology / Q000382:microbiology; D020082:Magnaporthe / Q000166:cytology / Q000254:growth & development* / Q000276:immunology / Q000472:pathogenicity*; D020675:Peroxisomes / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000382:microbiology; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D058305:Sorting Nexins / Q000378:metabolism*; D013172:Spores, Fungal / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000975:Antioxidants; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D058305:Sorting Nexins; D049452:Green Fluorescent Proteins; D005978:Glutathione