Abstract
LysM effectors play a relevant role during the plant colonization by successful phytopathogenic fungi, since they enable them to avoid either the triggering of plant defense mechanisms or their attack effects. Tal6, a LysM protein from Trichoderma atroviride, is capable of binding to complex chitin. However, until now its biological function is not completely known, particularly its participation in plant–Trichoderma interactions. We obtained T. atroviride Tal6 null mutant and Tal6 overexpressing strains and determined the role played by this protein during Trichoderma-plant interaction and mycoparasitism. LysM effector Tal6 from T. atroviride protects the hyphae from chitinases by binding to chitin of the fungal cell wall, increases the fungus mycoparasitic capacity, and modulates the activation of the plant defense system. These results show that beneficial fungi also employ LysM effectors to improve their association with plants.
Highlights
Effectors are molecules derived from microorganisms, like fungi, that participate in the establishment of its associations with other organisms, altering host structure and function (Selin et al, 2016); they were first described in pathogenic systems, playing an important role in facilitating pathogen infection or triggering host defense responses (Hogenhout et al, 2009)
We performed a bioinformatic analysis using the JGI database3 to determine the number of LysM motifs contained in each of the six genes reported as putative effectors for T. atroviride
We corroborated the expression of Tal6 during the interaction with A. thaliana at 2, 3, and 5 days of interaction, corresponding to T1, T2, and T3 of collect time (Figure 1A), by qRT-PCR and we observed that Tal6 was differentially up-regulated in the presence of A. thaliana at the three times collected, even before of a physical contact between roots and mycelia, with a relative expression of two times fold compared to the control (Figure 1B), suggesting that Tal6 could have a role in the establishment of the Trichoderma–plant interaction
Summary
Effectors are molecules derived from microorganisms, like fungi, that participate in the establishment of its associations with other organisms, altering host structure and function (Selin et al, 2016); they were first described in pathogenic systems, playing an important role in facilitating pathogen infection or triggering host defense responses (Hogenhout et al, 2009). The LysM motif is a carbohydrate-binding module, approximately of 50aa, that binds to N-acetyl-D-glucosamine (GlcNAc), the structural unit from chitin, chitosan and peptidoglycan. These effectors have a βααβ secondary structure, where both α-helices are packed on the same side of the two antiparallel β-sheet, and there can be several LysM motifs in one protein (Buist et al, 2008; De Jonge and Thomma, 2009)
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