Secreted Alpha-N-Arabinofuranosidase B Protein Is Required for the Full Virulence of Magnaporthe oryzae and Triggers Host Defences

Abstract

Rice blast disease caused by Magnaporthe oryzae is one of the most devastating fungal diseases of rice and results in a huge loss of rice productivity worldwide. During the infection process, M. oryzae secretes a large number of glycosyl hydrolase proteins into the host apoplast to digest the cell wall and facilitate fungal ingression into host tissues. In this study, we identified a novel arabinofuranosidase-B (MoAbfB) protein that is secreted by M. oryzae during fungal infection. Deletion of MoAbfB from M. oryzae resulted in reduced disease severity in rice. Biochemical assays revealed that the MoAbfB protein exhibited arabinofuranosidase activity and caused degradation of rice cell wall components. Interestingly, pre-treatment of rice with the MoAbfB protein inhibited fungal infection by priming defence gene expression. Our findings suggest that MoAbfB secretion affects M. oryzae pathogenicity by breaking down the host cell wall, releasing oligosaccharides that may be recognized by the host to trigger innate immune responses.

Genomes and secretomes of Ascomycota fungi reveal diverse functions in plant biomass decomposition and pathogenesis

“…Some proteins with annotated functions in plant biomass degradation and pathogenesis were expressed only in Chaetomium . One of these, alpha-N-arabinofuranosidase C (g2612.t1), functions in the degradation of arabinoxylan, a component of plant hemicellulose, and is also required for full virulence of rice blast fungus Magnaporthe oryzae [23]. Chitin synthase G (g5713.t1), also expressed by Chaetomium , may play a role in pathogenic plant interactions, as chitin synthesis plays a role in the virulence of the plant fungal pathogens Botrytis cinerea [24, 25], Magnaporthe oryzae [26], Fusarium oxysporum [27], Fusarium verticillioides [28], Fusarium asiaticum [29], Gibberella zeae [30], Colletotrichum graminicola [31] and Ustilago maydis [32, 33].…”

Mining the effector repertoire of the biotrophic fungal pathogen Ustilago hordei during host and non‐host infection

“…The effector repertoire of U. hordei contains cellulases, xylanases, β‐glucosidase, pectinases, α‐ l ‐arabinofuranosidases and exo‐ and endo‐glucanases, which can hydrolyse the main components of either plant or fungal cell walls. Recently, several studies have shown that fungal‐derived cellulases, endo‐1,4‐β‐xylanases and α‐ l ‐arabinofuranosidases are required for full virulence of Magnaporthe oryzae during rice colonization (Nguyen et al., ; Van Vu et al., ; Wu et al., ). Ustilago hordei may secrete these glycosyl hydrolase proteins into the host apoplast to degrade the host cell wall in order to facilitate host penetration or cell‐to‐cell passage by loosening the plant cell wall, or to possibly release nutrients from the host cell wall to support its own growth.…”

BcXYG1, a Secreted Xyloglucanase from Botrytis cinerea, Triggers Both Cell Death and Plant Immune Responses

“…Previous studies demonstrated that certain plant cell wall residues, such as oligogalacturonides and oligosaccharides that are released by enzymatic hydrolysis, could activate plant defense responses (Ferrari et al, 2013;Trouvelot et al, 2014;Benedetti et al, 2015;Wu et al, 2016). To eliminate the possible effect of xyloglucan hydrolysis products on plant systemic resistance, we used the xyloglucanase activity mutant MBcXYG1 for subsequent studies.…”

“…These enzymes hydrolyze the glycoside bond between two or more carbohydrates or between a carbohydrate and a noncarbohydrate residue, thereby reducing complex sugar polymers to simple sugars (Cantarel et al, 2009;Kubicek et al, 2014). Some CWDEs activate the plant immune response, either directly or through the release of cell wall elicitors (Poinssot et al, 2003;Zhang et al, 2014b;Benedetti et al, 2015;Ma et al, 2015;Wu et al, 2016), and also may induce necrosis when injected to plant tissues (Noda et al, 2010;Zhang et al, 2014bZhang et al, , 2015Ma et al, 2015). In certain cases, this necrosisinducing activity was found to be unrelated to the enzymatic activity, thus defining another class of NIPs.…”