Crop Diseases, Pests and Genetics Research Unit, USDA, Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, United States of America.
Foreign Disease and Weed Science Research Unit, USDA, Agricultural Research Service, Frederick, MD, United States of America.
PLoS One. 2020 Oct 2;15(10):e0240101. doi: 10.1371/journal.pone.0240101. eCollection 2020.
Bacterial phytopathogen Xylella fastidiosa specifically colonizes the plant vascular tissue through a complex process of cell adhesion, biofilm formation, and dispersive movement. Adaptation to the chemical environment of the xylem is essential for bacterial growth and progression of infection. Grapevine xylem sap contains a range of plant secondary metabolites such as phenolics, which fluctuate in response to pathogen infection and plant physiological state. Phenolic compounds are often involved in host-pathogen interactions and influence infection dynamics through signaling activity, antimicrobial properties, and alteration of bacterial phenotypes. The effect of biologically relevant concentrations of phenolic compounds coumaric acid, gallic acid, epicatechin, and resveratrol on growth of X. fastidiosa was assessed in vitro. None of these compounds inhibited bacterial growth, but epicatechin and gallic acid reduced cell-surface adhesion. Cell-cell aggregation decreased with resveratrol treatment, but the other phenolic compounds tested had minimal effect on aggregation. Expression of attachment (xadA) and aggregation (fimA) related genes were altered by presence of the phenolic compounds, consistent with observed phenotypes. All four of the phenolic compounds bound to purified X. fastidiosa lipopolysaccharide (LPS), a major cell-surface component. Information regarding the impact of chemical environment on pathogen colonization in plants is important for understanding the infection process and factors associated with host susceptibility.
细菌病原体韧皮部坏死病菌（Xylella fastidiosa）通过细胞黏附、生物膜形成和分散运动等复杂过程，专门定殖于植物维管组织。适应木质部的化学环境对于细菌生长和感染进展至关重要。葡萄木质部汁液中含有一系列植物次生代谢物，如酚类化合物，这些化合物会响应病原体感染和植物生理状态而波动。酚类化合物通常参与宿主-病原体相互作用，并通过信号活性、抗菌特性和改变细菌表型来影响感染动态。评估了生物相关浓度的酚类化合物（咖啡酸、没食子酸、表儿茶素和白藜芦醇）对韧皮部坏死病菌生长的影响。这些化合物都没有抑制细菌生长，但表儿茶素和没食子酸降低了细胞表面黏附。用白藜芦醇处理后细胞-细胞聚集减少，但其他测试的酚类化合物对聚集的影响很小。存在酚类化合物时，附着（xadA）和聚集（fimA）相关基因的表达发生改变，与观察到的表型一致。这四种酚类化合物都与纯化的韧皮部坏死病菌脂多糖（LPS）结合，LPS 是主要的细胞表面成分。关于化学环境对植物病原体定殖影响的信息对于理解感染过程和与宿主易感性相关的因素非常重要。
