Rise of a Cereal Killer: The Biology of Magnaporthe oryzae Biotrophic Growth

The rice blast fungus, Magnaporthe oryzae, causes one of the most destructive diseases of cultivated rice in the world. Infections caused by this recalcitrant pathogen lead to the annual destruction of approximately 10–30% of the rice harvested globally. The fungus undergoes extensive developmental changes to be able to break into plant cells, build elaborate infection structures, and proliferate inside host cells without causing visible disease symptoms. From a molecular standpoint, we are still in the infancy of understanding how M. oryzae manipulates the host during this complex multifaceted infection. Here, we describe recent advances in our understanding of the cell biology of M. oryzae biotrophic interaction and key molecular factors required for the disease establishment in rice cells. The internalization and transport of the G-protein signaling components to late endosomal compartments play a critical role during appressoria development in rice blast disease. TOR pathway activation by intracellular glutamine levels negatively regulates appressorium development. Rice blast fungus has evolved two secretion mechanisms to deliver effector proteins into the host cell during biotrophic growth. M. oryzae disrupts hormonal homeostasis to evade or suppress host defenses during plant cell invasion.