草菇响应假单胞菌(Pseudomonas sp.) Z9侵染后的代谢组分析

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

摘要:

【背景】假单胞菌(Pseudomonassp.) Z9是引起草菇黄斑病的病原，称之为草菇黄斑病菌，但其致病机制尚未明确。【目的】研究草菇黄斑病菌侵染草菇后的差异代谢物及代谢通路，为认识其致病机制提供依据。【方法】以被病菌侵染前后不同时间的草菇子实体为材料，测定其细胞膜透性的丙二醛(malondialdehyde,MDA)和相对电导率的变化，以及活性氧代谢相关酶即超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)和多酚氧化酶(polyphenol oxidase,PPO)的活性变化，同时利用非靶向代谢组学探究菌株Z9侵染草菇24 h后的代谢物差异。【结果】接种病菌48 h内的草菇MDA含量随时间延长呈上升趋势，且均显著高于CK组(P<0.05)；CAT和SOD活性随时间延长逐渐上升，24 h时达到峰值，PPO活性则先下降后上升；两组处理草菇相对电导率均呈先上升后趋于稳定的趋势，12 h后趋于稳定；草菇两组样本间的代谢物差异显著，共筛选并鉴定出131个差异代谢物。KEGG通路富集分析发现差异代谢物主要富集在氨基酸代谢途径，其中色氨酸代谢和酪氨酸代谢是差异代谢物富集最多的通路。丁香酸是草菇被黄斑病菌Z9侵染后含量增加最大的代谢物，其计算变量投影重要度(variable important for the projection,VIP)值达1.355 6。【结论】草菇受黄斑病菌侵染后细胞膜被持续过氧化；推测草菇通过产生丁香酸清除由Pseudomonas sp.Z9刺激产生的活性氧(reactive oxygen species,ROS)来避免细胞氧化损伤，酪氨酸代谢途径是病原侵染草菇产生病斑的一个重要代谢途径。

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.