Symplastic effector protein trafficking during biotrophic invasion of rice cells by the blast fungus
B. VALENT (1), E. Oliveira-Garcia (1), H. Zheng (1), M. Yi (2), P. Migeon (1), M. Dalby (1), K. Park (1), S. Park (1), M. Farman (3), Z. Wang (4), J. Zhou (4) (1) Kansas State University, U.S.A.; (2) The Noble Foundation, U.S.A.; (3) University of Kentucky, U.S.A.; (4) Fujian Agriculture and Forestry University, China

The hemibiotrophic rice blast fungus Magnaporthe oryzae (synonym Pyricularia oryzae) differentiates specialized invasive hyphae (IH) that invade living rice cells. Biotrophic invasive hyphae grow while enclosed in host-derived extrainvasive-hyphal membrane. Immediately after entry into a host cell, the fungus undergoes a characteristic morphological switch, and the hyphal cells that undergo this switch are associated with a specialized interfacial structure, the biotrophic interfacial complex (BIC). So far, we have identified 30 BIC-localized effectors that are translocated into the cytoplasm of invaded rice cells and move ahead into neighboring rice cells before fungal invasion. These symplastic effectors accumulate in BICs via a Golgi-independent secretion system involving the exocyst complex. New higher-resolution live cell imaging shows symplastic effectors that appear packaged into vesicles in and around BICs. Symplastic effectors Bas1, Pwl1 and Pwl2 appear sorted into different micro-vesicles in BICs at the tips of primary hyphae. BICs on mature bulbous hypha are associated with effectors in fewer, larger vesicles, which at times reach diameter sizes over 3 µm. Wortmannin, a presumed plant endocytosis inhibitor, induces abnormally-shaped and swollen BICs and symplastic effectors appear restricted to BICs in the presence of the chemical. Our working hypothesis is that symplastic effectors are internalized into living rice cells via endocytosis.


Abstract Number: C22-2
Session Type: Concurrent