Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China.
Kiwifruit Engineering and Technology Research Center, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China.
Phytopathology. 2022 Aug;112(8):1610-1619. doi: 10.1094/PHYTO-09-21-0404-R. Epub 2022 Jul 1.
The type III secretion system (T3SS) is a key factor in the pathogenesis of pv. biovar 3 (3), the causal agent of a global kiwifruit bacterial canker pandemic. To monitor the T3SS expression levels in 3, we constructed a luciferase reporter plasmid-expressing HrpA-NLuc fusion protein. The expression of HrpA-NLuc was induced in -inducing conditions whereas the level of luciferase activity correlated with the expression of / genes in 3 confirmed the reliability of the reporter construct. Based on the readout of the NLuc reporter construct, three small molecule compounds 4-methoxy-cinnamic acid, sulforaphane, and ferulic acid were determined as T3SS inhibitors in 3, whereas sodium acetate was determined to be a T3SS inducer. Moreover, the aqueous extract of fruit inhibited the accumulation of HrpA-NLuc in 3 in medium and in planta. Additionally, the T3SS inhibitors suppress 3 virulence, whereas the T3SS inducer promotes 3 virulence on kiwifruit. Thus, our findings may provide clues to why the fruit is not infected by 3, and the 3 T3SS inhibitors have potential as alternatives to current nonspecific antimicrobials for disease management.
III 型分泌系统（T3SS）是 pv. biovar 3（3）发病机制的关键因素，pv. biovar 3（3）是一种全球性猕猴桃细菌性溃疡病大流行的病原体。为了监测 3 中的 T3SS 表达水平，我们构建了一个表达 HrpA-NLuc 融合蛋白的荧光素酶报告质粒。在 -诱导条件下诱导 HrpA-NLuc 的表达，而荧光素酶活性的水平与 / 基因的表达相关，这证实了报告构建体的可靠性。基于 NLuc 报告构建体的读数，确定了三种小分子化合物 4-甲氧基肉桂酸、萝卜硫素和阿魏酸是 3 中的 T3SS 抑制剂，而乙酸钠被确定为 T3SS 诱导剂。此外，水果的水提物抑制了 3 在培养基中和植物体内 HrpA-NLuc 的积累。此外，T3SS 抑制剂抑制 3 的毒力，而 T3SS 诱导剂促进 3 在猕猴桃上的毒力。因此，我们的发现可能提供了为什么水果不受 3 感染的线索，并且 3 的 T3SS 抑制剂有可能替代当前非特异性抗菌药物用于疾病管理。
