Pring, S. | Search bioRxiv

bioRxiv2024

Botrytis cinerea detoxifies the sesquiterpenoid phytoalexin rishitin through multiple metabolizing pathways

Botrytis cinerea is a necrotrophic pathogen that infects across a broad range of plant hosts, including high-impact crop species. Its generalist necrotrophic behavior stems from its ability to detoxify structurally diverse phytoalexins. The current study aims to provide evidence of the ability of B. cinerea to tolerate the sesquiterpenoid phytoalexin rishitin, which is produced by potato and tomato. While the growth of potato pathogens Phytophthora infestans (late blight) and Alternaria solani (early blight) was severely inhibited by rishitin, B. cinerea was tolerant to rishitin. After incubation of rishitin with the mycelia of B. cinerea, it was metabolized to at least six oxidized forms. Structural analysis of these purified rishitin metabolites revealed a variety of oxidative metabolism including hydroxylation at C7 or C12, ketone formation at C5, and dihydroxylation at the 10,11-olefin. Six rishitin metabolites showed reduced toxicity to P. infestans and A. solani, indicating that B. cinerea has at least 5 distinct enzymatic reactions to detoxify rishitin. Four host-specialized phytopathogenic Botrytis species, namely B. elliptica, B. allii, B. squamosa, and B. tulipae also had at least a partial ability to metabolize rishitin as B. cinerea, but their metabolic capacity was significantly weaker than that of B. cinerea. These results suggest that the ability of B. cinerea to rapidly metabolize rishitin through multiple detoxification mechanisms could be critical for its pathogenicity in potato and tomato.

microbiology↗

bioRxiv2023

Induction of plant disease resistance by mixed oligosaccharide elicitors prepared from plant cell wall and crustacean shells

Basal plant immune responses are activated by the recognition of the conserved pathogen-associated molecular patterns (PAMPs), or breakdown molecules released from plants after damage by pathogen infection, so-called danger-associated molecular patterns (DAMPs). While chitin-oligosaccharide (CHOS), a primary component of the fungal cell wall, is most known as PAMP, plant cell wall-derived oligosaccharides, cello-oligosaccharides (COS) from cellulose and xylo-oligosaccharide (XOS) from hemicellulose, are representative DAMPs, which activate signaling steps similar to PAMP-induced immunity to elicit defenses and provide protection against pathogens. In this study, elicitor activities of COS prepared from cotton linters, XOS prepared from corn cobs as well as chitin-oligosaccharide (CHOS) from crustacean shells were comparatively investigated. In Arabidopsis, treatment of COS, XOS or CHOS triggered typical defense responses such as reactive oxygen species (ROS) production, activation of MAP kinases phosphorylation, callose depositions, and activation of the promoter for defense-related transcription factor WRKY33. When COS, XOS and CHOS were used at concentrations with similar activity in inducing ROS production and callose depositions, CHOS was particularly highly potent in activating the MAPK kinases and WRKY33 promoters. Among the COS and XOS with different degrees of polymerization (DP), cellotriose (DP3) and xylotetraose (DP4) showed the highest activity for the activation of WRKY33 promoter. Simultaneous treatment of COS, XOS and CHOS leads to a strong transcriptional change for defense-related genes, and gene ontology (GO) enrichment analysis of RNAseq data revealed that a mixture of three oligosaccharide (oligo-mix) effectively activate the plants disease resistance. In practice, treatment of the oligo-mix enhanced the resistance of tomato to powdery mildew, but plant growth was not inhibited but rather tended to be promoted, providing evidence that mixed oligosaccharides have beneficial effects on improving disease resistance in plants, making them a promising class of compounds for practical application.

plant biology↗