Metabolomics of Volvariella volvacea in response to infection by Pseudomonas sp. Z9

Abstract:

[Background] Pseudomonas sp. Z9 is the pathogen responsible for causing yellow blotch disease in Volvariella volvacea. However, the mechanism of this pathogen in inducing yellow blotch disease remains unclear. [Objective] To investigate the differential metabolites and metabolic pathways of V. volvacea infected by Pseudomonas sp. Z9, providing a basis for understanding the underlying mechanism. [Methods] V. volvacea fruiting bodies inoculated with the pathogen and sterile water (CK) were sampled every 12 h within 48 h. The content of malondialdehyde (MDA) and the relative conductivity of the fruiting bodies were measured. Meanwhile, the activities of superoxide dismutase (SOD), catalase (CAT), and polyphenol oxidase (PPO) associated with the metabolism of reactive oxygen species were determined. Non-targeted metabolomics was employed to explore the differential metabolites and pathways of Pseudomonas sp. Z9-infected V. volvacea 24 h post-infection. [Results] The MDA content of V. volvacea increased over time within 48 h after inoculation of the pathogen and was higher in the inoculation group than in the CK group (P<0.05). CAT and SOD activities gradually increased over time and reached the peak at the time point of 24 h, while the PPO activity first decreased and then increased. The relative conductivity of the two groups first increased and then reached stability after 12 h. A total of 131 differential metabolites between the two groups were screened out and identified. The KEGG pathway enrichment results revealed that the differential metabolites were mainly enriched in amino acid metabolism pathways, especially tryptophan metabolism and tyrosine metabolism. Syringic acid was the metabolite with the largest increase in content after infection by Pseudomonas sp. Z9 in V. volvacea, with a variable important for the projection (VIP) value of 1.355 6. [Conclusion] The cell membrane of V. volvacea infected by Pseudomonas sp. Z9 experiences persistent peroxidation. We hypothesize that V. volvacea utilizes syringic acid to eliminate reactive oxygen species produced upon infection of Pseudomonas sp. Z9, thus avoiding cellular oxidative damage. Tyrosine metabolism is an important metabolic pathway involved in the formation of yellow blotches caused by Pseudomonas sp. Z9 in V. volvacea.