ROS is able to kill the pathogen directly or facilitate the biosynthesis of antimicrobial compounds. oryzae infection is characterized by the accumulation of reactive oxygen species (ROS) and deposition of phenolic compounds, etc.
Plants have evolved two branches of immune systems, the pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and the effector-triggered immunity (ETI Jones and Dangl, 2006). During an incompatible interaction, resistant plants deploy their immune system that either limits the germination and development of a conidium, or constrains the growth of the penetration peg and hyphae to prevent infection (Hasegawa et al., 2010). IH further invade neighboring cells via plasmodesmata, continuing the infection in neighboring cells (Kankanala et al., 2007). During a compatible interaction, the primary hyphae differentiate into thicker and bulbous invasive hyphae (IH) and eventually fill the cell. The germ tube develops into a melanized appressorium that can mechanically breach the cell surface and develop a penetration peg to enter the epidermal cell (Kankanala et al., 2007 Marcel et al., 2010). Under favorable conditions, the conidium germinates and produces a germ tube within hours. The life cycle of the pathogen begins with a conidium, which lands on and adheres to a leaf surface. Rice blast, caused by the hemibiotrophic fungal pathogen Magnaporthe oryzae, is a major disease that threatens rice production.
Rice is an economically important crop that feeds more than half of the world's population (Liu et al., 2014). Therefore, the involvement of ethylene signaling in disease resistance is probably by activation of ROS and phytoalexin production in rice during M. These data suggest that OsEIN2-mediated OsrbohA/OsrbohB and OsOPR transcription may play essential roles in ROS generation, JA biosynthesis and the subsequent phytoalexin accumulation. Furthermore, we demonstrated that OsEIL1 binds to the promoters of OsrbohA/OsrbohB and OsOPR4 to activate their expression. Transcription of OsrbohA/B, which encode NADPH oxidases, and OsOPRs, the JA biosynthesis genes, were induced by M. Whole-genome transcription analysis revealed that responsive genes of ethylene, jasmonates (JAs) and reactive oxygen species (ROS) signaling as well as phytoalexin biosynthesis genes were remarkably induced. Mutation of OsEIN2 led to enhanced disease susceptibility. Ethylene signaling components OsEIN2 and the downstream transcription factor OsEIL1 positively regulated disease resistance.
Resistant rice cultivars accumulated higher levels of ethylene than susceptible ones. In this study, we showed that the blast fungus Magnaporthe oryzae infection activated ethylene biosynthesis in rice. However, the roles of ethylene signaling in immune responses remain largely unknown. Ethylene plays diverse roles in plant growth, development and stress responses.
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