State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, and College of Life Science and Technology, Guangxi University, Nanning, Guangxi 530004, China.
National Biofilms Innovation Centre, Biological Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom.
Phytopathology. 2021 Jul;111(7):1104-1113. doi: 10.1094/PHYTO-08-20-0372-R. Epub 2021 Sep 10.
As with many phytopathogenic bacteria, the virulence of pv. , the causal agent of black rot disease in cruciferous plants, relies on secretion of a suite of extracellular enzymes that includes cellulase (endoglucanase), pectinase, protease, and amylase. Although the role in virulence of a number of these enzymes has been assessed, the contribution of amylase to pv. virulence has yet to be established. In this work, we investigated both the role of extracellular amylase in pv. virulence and the control of its expression. Deletion of (here renamed ), a putative amylase-encoding gene from the genome of pv. strain 8004, resulted in a complete loss of extracellular amylase activity and significant reduction in virulence. The extracellular amylase activity and virulence of the mutant could be restored to the wild-type level by expressing in trans. These results demonstrated that is responsible for the extracellular amylase activity of pv. and indicated that extracellular amylase plays an important role in pv. virulence. We also found that the expression of is strongly induced by starch and requires activation by the global posttranscriptional regulator RsmA. RsmA binds specifically to the 5'-untranslated region of transcripts, suggesting that RsmA regulates directly at the posttranscriptional level. Unexpectedly, in addition to posttranscriptional regulation, the use of a transcriptional reporter demonstrated that RsmA also regulates expression at the transcriptional level, possibly by an indirect mechanism.
与许多植物病原菌一样，芸薹假单胞菌 pv. 的致病力依赖于分泌一系列细胞外酶，包括纤维素酶（内切葡聚糖酶）、果胶酶、蛋白酶和淀粉酶。虽然已经评估了其中一些酶在致病力中的作用，但淀粉酶对 pv. 致病力的贡献尚未确定。在这项工作中，我们研究了细胞外淀粉酶在 pv. 致病力中的作用及其表达的控制。从 pv. 菌株 8004 的基因组中删除一个假定的淀粉酶编码基因（此处更名为），导致细胞外淀粉酶活性完全丧失，毒力显著降低。通过在转座体中表达，可使突变体的细胞外淀粉酶活性和毒力恢复到野生型水平。这些结果表明是 pv. 细胞外淀粉酶活性的原因，并表明细胞外淀粉酶在 pv. 致病力中起着重要作用。我们还发现的表达受淀粉强烈诱导，并需要全局转录后调节因子 RsmA 的激活。RsmA 特异性结合到转录物的 5'-非翻译区，表明 RsmA 直接在转录后水平调节。出乎意料的是，除了转录后调节外，使用转录报告基因表明 RsmA 还通过间接机制在转录水平上调节的表达。
