Zhu Ping-Chuan, Li Yi-Ming, Yang Xia, Zou Hai-Fan, Zhu Xiao-Lin, Niu Xiang-Na, Xu Ling-Hui, Jiang Wei, Huang Sheng, Tang Ji-Liang, He Yong-Qiang
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China.
Res Microbiol. 2020 Mar;171(2):64-73. doi: 10.1016/j.resmic.2019.10.004. Epub 2019 Oct 30.
The type VI secretion system (T6SS), a multifunctional protein secretion device, plays very important roles in bacterial killing and/or virulence to eukaryotic cells. Although T6SS genes have been found in many Xanthomonas species, the biological function of T6SSs has not been elucidated in most xanthomonads. In this study, we identified two phylogenetically distinct T6SS clusters, T6SS1 and T6SS2, in a newly sequenced Chinese strain GX01 of Xanthomonas oryzea pv. oryzicola (Xoc) which causes bacterial leaf streak (BLS) of rice (Oryza sativa L.). Mutational assays demonstrated that T6SS1 and T6SS2 are not required for the virulence of Xoc GX01 on rice. Nevertheless, we found that T6SS2, but not T6SS1, played an important role in bacterial killing. Transcription and secretion analysis revealed that hcp2 gene is actively expressed and that Hcp2 protein is secreted via T6SS. Moreover, several candidate T6SS effectors were predicted by bioinformatics analysis that might play a role in the antibacterial activity of Xoc. This is the first report to investigate the type VI secretion system in Xanthomonas oryzae. We speculate that Xoc T6SS2 might play an important role in inter-bacterial competition, allowing this plant pathogen to gain niche advantage by killing other bacteria.
VI型分泌系统（T6SS）是一种多功能蛋白质分泌装置，在细菌对真核细胞的杀伤和/或毒力方面发挥着非常重要的作用。尽管在许多黄单胞菌属物种中都发现了T6SS基因，但在大多数黄单胞菌中，T6SS的生物学功能尚未阐明。在本研究中，我们在新测序的引起水稻细菌性条斑病（BLS）的水稻黄单胞菌致病变种（Xoc）中国菌株GX01中鉴定出两个系统发育上不同的T6SS簇，即T6SS1和T6SS2。突变分析表明，T6SS1和T6SS2对于Xoc GX01对水稻的毒力不是必需的。然而，我们发现T6SS2而非T6SS1在细菌杀伤中起重要作用。转录和分泌分析表明，hcp2基因被积极表达，并且Hcp2蛋白通过T6SS分泌。此外，通过生物信息学分析预测了几个可能在Xoc的抗菌活性中起作用的候选T6SS效应子。这是首次对水稻黄单胞菌中的VI型分泌系统进行研究的报告。我们推测Xoc T6SS2可能在细菌间竞争中起重要作用，使这种植物病原体通过杀死其他细菌而获得生态位优势。
