Septin-Dependent Assembly of the Exocyst Is Essential for Plant Infection by Magnaporthe oryzae

Abstract

Magnaporthe oryzae is the causal agent of rice blast disease, the most devastating disease of cultivated rice (Oryza sativa) and a continuing threat to global food security. To cause disease, the fungus elaborates a specialized infection cell called an appressorium, which breaches the cuticle of the rice leaf, allowing the fungus entry to plant tissue. Here, we show that the exocyst complex localizes to the tips of growing hyphae during vegetative growth, ahead of the Spitzenkörper, and is required for polarized exocytosis. However, during infection-related development, the exocyst specifically assembles in the appressorium at the point of plant infection. The exocyst components Sec3, Sec5, Sec6, Sec8, and Sec15, and exocyst complex proteins Exo70 and Exo84 localize specifically in a ring formation at the appressorium pore. Targeted gene deletion, or conditional mutation, of genes encoding exocyst components leads to impaired plant infection. We demonstrate that organization of the exocyst complex at the appressorium pore is a septin-dependent process, which also requires regulated synthesis of reactive oxygen species by the NoxR-dependent Nox2 NADPH oxidase complex. We conclude that septinmediated assembly of the exocyst is necessary for appressorium repolarization and host cell invasion.

Clathrin localization and dynamics in Aspergillus nidulans

“…We previously published details of the endocytic marker FimA in A. nidulans (Upadhyay and Shaw, ) which did not include an examination of the lifetime of fimbrin endocytic patches. Fimbrin has since been shown to show similar localization in a variety of filamentous fungi (Castillo‐Lluva et al ., ; Delgado‐Álvarez et al ., ; Gupta et al ., ). Here, we observed that these structures appear to dissipate more rapidly in hyphae than in budding yeast (∼9 s vs ∼12 s) (Kim et al ., ).…”

Fungal Morphogenesis, from the Polarized Growth of Hyphae to Complex Reproduction and Infection Structures

“…2), a conserved octameric tethering complex first discovered in yeast. Exocyst components have been found in filamentous fungi at growth sites (45,46). In the larger hyphae of N. crassa, the subcellular organization of the apex can be more distinctly resolved by confocal laser scanning microscopy.…”

Sorting nexin (MoVps17) is required for fungal development and plant infection by regulating endosome dynamics in the rice blast fungus

“…M. oryzae has emerged as an excellent model system for studying plant-fungal pathogen interactions for easy genetic manipulation and functional analysis (Talbot, 2003;Wilson and Talbot, 2009;Li et al, 2012). In recent years, a number of intracellular trafficking pathways have been shown to be important for M. oryzae plant infection, including exocytosis, endocytosis, retromer-mediated autophagy and septin-mediated cytoskeletal remodelling and dynamin-mediated peroxisomal and mitochondrial fission (Dagdas et al, 2012;Ryder et al, 2013;Gupta et al, 2015;Liu et al, 2015;Qi et al, 2016;Zhong et al, 2016).…”