Molecular Plant-Microbe Interactions

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Plants fight microbial attacks using both constitutive and induced defenses which include RNA silencing, basal and highly specific resistance. Basal resistance (PTI, for PAMP Triggered Immunity) is very often mediated via the detection of pathogen-associated molecular patterns (PAMPs). However, adapted microbes express a suite of effector proteins that often act to suppress these defenses. Plants have evolved other receptors called resistance proteins (R proteins) that detect these pathogen effectors and activate strong defenses called Effector Triggered Immunity (ETI). RNA silencing is a nucleotide sequence-specific RNA turnover mechanism that is highly conserved among eukaryotes. Common features of the RNA silencing in different organisms are the involvement of double-stranded (ds)RNA as initiator molecule and the presence of small (s)RNAs of 21-25nt that are processed from dsRNA by an RNAse III-like enzyme named Dicer. The sRNAs confer sequence specificity to a RNA-induced silencing complex (RISC) featuring a nuclease that degrades any RNA-sharing sequence homology to the activating dsRNA molecules. During the last funding period we showed that plant pathogens use several strategies, including suppression of immunity, manipulation of host genes, to enable disease. We also showed that plant is able to sense a suppressor of RNAi pathway as a counter-counter defense strategy to induce ETI. In the next funding, I will focus on how salicylic acid induces virulence of some pathogens, how plant pathogens manipulate host genes to suppress innate immunity and how plant sense a suppressor of RNAi pathway leading to activation of ETI. The knowledge obtained will contribute to the development of new strategies to better manage the disease problems not only in Canada, but around the world.