The type VI secretion system (T6SS) of many gram‐negative bacteria injects toxic effectors into adjacent cells to manipulate host cells during pathogenesis or to kill competing bacteria. However, the identification and function of the T6SS effectors remains only partly known. Pantoea ananatis, a gram‐negative bacterium, is commonly found in various plants and natural environments, including water and soil. In the current study, genomic analysis of P. ananatis DZ‐12 causing brown stalk rot on maize demonstrated that it carries three T6SS gene clusters, namely, T6SS‐1, T6SS‐2, and T6SS‐3. Interestingly, only T6SS‐1 secretion systems are involved in pathogenicity and bacterial competition. The study also investigated the T6SS‐1 system in detail and identified an unknown T6SS‐1‐secreted effector TseG by using the upstream T6SS effector chaperone TecG containing a conserved domain of DUF2169. TseG can directly interact with the chaperone TecG for delivery and with a downstream immunity protein TsiG for protection from its toxicity. TseG, highly conserved in the Pantoea genus, is involved in virulence in maize, potato, and onion. Additionally, P. ananatis uses TseG to target Escherichia coli, gaining a competitive advantage. This study provides the first report on the T6SS‐1‐secreted effector from P. ananatis, thereby enriching our understanding of the various types and functions of type VI effector proteins.

中文翻译：

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Pantoea ananatis VI 型分泌系统效应子 TseG 参与毒力和抗菌活性

许多革兰氏阴性细菌的 VI 型分泌系统 (T6SS) 将有毒效应物注入邻近细胞，以在发​​病过程中操纵宿主细胞或杀死竞争细菌。然而，T6SS 效应器的识别和功能仍然只有部分已知。菠萝泛菌是一种革兰氏阴性细菌，常见于各种植物和自然环境，包括水和土壤中。在当前的研究中，基因组分析菠萝引起玉米茎秆褐腐病的 DZ-12 表明其携带三个 T6SS 基因簇，即 T6SS-1、T6SS-2 和 T6SS-3。有趣的是，只有 T6SS-1 分泌系统参与致病性和细菌竞争。该研究还详细研究了 T6SS-1 系统，并通过使用含有 DUF2169 保守结构域的上游 T6SS 效应分子伴侣 TecG 鉴定了未知的 T6SS-1 分泌效应子 TseG。TseG 可以直接与分子伴侣 TecG 相互作用进行递送，并与下游免疫蛋白 TsiG 相互作用以防止其毒性。TseG，高度保守泛菌属属，与玉米、马铃薯和洋葱的毒力有关。此外，菠萝使用 TseG 来定位大肠杆菌，获得竞争优势。本研究首次报告了 T6SS-1 分泌的效应子菠萝，从而丰富了我们对VI型效应蛋白的各种类型和功能的理解。