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On the mechanism of translocation of Magnaporthe oryzae effectors into rice cells

Ely Oliveira Garcia: Kansas State University

<div>Rice blast caused by <em>Magnaporthe oryzae </em>is the most destructive disease of rice worldwide. <em>M. oryzae</em> secretes various effectors, which are hypothesized to be involved in effective host infection. To date, little is known about the mechanisms of effector uptake into plant cells. Here we show translocation of the cytoplasmic effectors Bas1, Pwl1 and Pwl2 in vesicles from the biotrophic interfacial complex (BIC) to rice cytoplasm during biotrophic development. Using fluorescent protein tagging, we found that cytoplasmic effectors Bas1, Pwl1 and Pwl2 are sorted into different vesicles in BICs formed on primary hyphae, revealing new levels of functional complexity for this biotrophic structure. Additionally, the effector Bas83 is plant plasma membrane- and BIC-localized, suggesting a potential role in vesicle formation. Through FM4-64 labeling and Lit6b:eGFP transgenic rice colocalization assays, we demonstrated that the vesicles containing effectors originate from plant plasma membrane. Furthermore, plant endocytosis inhibitors and Virus-Induced Gene Silencing of rice endocytosis components induce abnormally-shaped and swollen BICs, accumulation of cytoplasmic effectors in BICs, as well as the accumulation of the cytoplasmic effectors under penetration pores. Based on these results we conclude that cytoplasmic effector translocation is mediated by vesicle formation and may be characteristic of appressoria as well as biotrophic invasive hyphae.</div>

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