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Deacetylation of chitin oligomers by Fusarium graminearum polysaccharide deacetylase suppresses plant immunity.

ABSTRACT: Chitin is a long-chain polymer of β-1,4-linked N-acetylglucosamine that forms rigid microfibrils to maintain the hyphal form and protect it from host attacks. Chitin oligomers are first recognized by the plant receptors in the apoplast region, priming the plant's immune system. Here, seven polysaccharide deacetylases (PDAs) were identified and their activities on chitin substrates were investigated via systematic characterization of the PDA family from Fusarium graminearum. Among these PDAs, FgPDA5 was identified as an important virulence factor and was specifically expressed during pathogenesis. ΔFgpda5 compromised the pathogen's ability to infect wheat. The polysaccharide deacetylase structure of FgPDA5 is essential for the pathogenicity of F. graminearum. FgPDA5 formed a homodimer and accumulated in the plant apoplast. In addition, FgPDA5 showed a high affinity toward chitin substrates. FgPDA5-mediated deacetylation of chitin oligomers prevented activation of plant defence responses. Overall, our results identify FgPDA5 as a polysaccharide deacetylase that can prevent chitin-triggered host immunity in plant apoplast through deacetylation of chitin oligomers.

SUBMITTER: Hu S

PROVIDER: S-EPMC10632789 | biostudies-literature | 2023 Dec

REPOSITORIES: biostudies-literature

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Deacetylation of chitin oligomers by Fusarium graminearum polysaccharide deacetylase suppresses plant immunity.

Hu Su S Jin Minxia M Xu Yangjie Y Wu Qin Q Jiang Qiantao Q Ma Jian J Zhang Yazhou Y Qi Pengfei P Chen Guoyue G Jiang Yunfeng Y Zheng Youliang Y Wei Yuming Y Xu Qiang Q

Molecular plant pathology 20230925 12

Chitin is a long-chain polymer of β-1,4-linked N-acetylglucosamine that forms rigid microfibrils to maintain the hyphal form and protect it from host attacks. Chitin oligomers are first recognized by the plant receptors in the apoplast region, priming the plant's immune system. Here, seven polysaccharide deacetylases (PDAs) were identified and their activities on chitin substrates were investigated via systematic characterization of the PDA family from Fusarium graminearum. Among these PDAs, FgP ...[more]

PMID: 37746915

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Project description:Partially acetylated chitosan oligosaccharides (paCOS) are potent biologics with many potential applications, and their bioactivities are believed to be dependent on their structure, i.e., their degrees of polymerization and acetylation, as well as their pattern of acetylation. However, paCOS generated via chemical N-acetylation or de-N-acetylation of GlcN or GlcNAc oligomers, respectively, typically display random patterns of acetylation, making it difficult to control and predict their bioactivities. In contrast, paCOS produced from chitin deacetylases (CDAs) acting on chitin oligomer substrates may have specific patterns of acetylation, as shown for some bacterial CDAs. However, compared to what we know about bacterial CDAs, we know little about the ability of fungal CDAs to produce defined paCOS with known patterns of acetylation. Therefore, we optimized the expression of a chitin deacetylase from the fungus Puccinia graminis f. sp. tritici in Escherichia coli The best yield of functional enzyme was obtained as a fusion protein with the maltose-binding protein (MBP) secreted into the periplasmic space of the bacterial host. We characterized the MBP fusion protein from P. graminis (PgtCDA) and tested its activity on different chitinous substrates. Mass spectrometric sequencing of the products obtained by enzymatic deacetylation of chitin oligomers, i.e., tetramers to hexamers, revealed that PgtCDA generated paCOS with specific acetylation patterns of A-A-D-D, A-A-D-D-D, and A-A-D-D-D-D, respectively (A, GlcNAc; D, GlcN), indicating that PgtCDA cannot deacetylate the two GlcNAc units closest to the oligomer's nonreducing end. This unique property of PgtCDA significantly expands the so far very limited library of well-defined paCOS available to test their bioactivities for a wide variety of potential applications.ImportanceWe successfully achieved heterologous expression of a fungal chitin deacetylase gene from the basidiomycete Puccinia graminis f. sp. tritici in the periplasm of E. coli as a fusion protein with the maltose-binding protein; this strategy allows the production of these difficult-to-express enzymes in sufficient quantities for them to be characterized and optimized through protein engineering. Here, the recombinant enzyme was used to produce partially acetylated chitosan oligosaccharides from chitin oligomers, whereby the pronounced regioselectivity of the enzyme led to the production of defined products with novel patterns of acetylation. This approach widens the scope for both the production and functional analysis of chitosan oligomers and thus will eventually allow the detailed molecular structure-function relationships of biologically active chitosans to be studied, which is essential for developing applications for these functional biopolymers for a circular bioeconomy, e.g., in agriculture, medicine, cosmetics, and food sciences.

Dataset Information

Deacetylation of chitin oligomers by Fusarium graminearum polysaccharide deacetylase suppresses plant immunity.

Publications

Deacetylation of chitin oligomers by Fusarium graminearum polysaccharide deacetylase suppresses plant immunity.

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