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Journal of Integrative Agriculture  2025, Vol. 24 Issue (5): 1844-1859    DOI: 10.1016/j.jia.2023.10.017
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Sigma factor 70 RpoD contributes to virulence by regulating cell motility, oxidative stress tolerance, and manipulating the expression of hrpG and hrpX in Xanthomonas oryzae pv. oryzae

Zhizhou Xu1, 3, Guichun Wu4, Bo Wang3, Baodian Guo3, Cong Sheng3, Yangyang Zhao3, Bao Tang3, Yancun Zhao3, Fengquan Liu1, 2, 3#

1 Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China

2 Department of Plant Pathology/Key Laboratory of Agricultural Microbiology, College of Agriculture, Guizhou University, Guiyang 550025, China

3 Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Food Quality and Safety–State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing 210014, China

4 National Engineering Laboratory of Crop Stress Resistance Breeding, School of Life Sciences, Anhui Agricultural University, Hefei 230036, China 

 Highlights 
The sigma 70 factor PXO_RpoD in Xanthomonas oryzae pv. oryzae governs bacterial motility, antioxidant responses, and virulence in rice, highlighting its essential role in pathogenicity.
PXO_RpoD activates the transcription of hrpG and hrpX, revealing upstream regulatory mechanisms that control the type III secretion system in Xanthomonas oryzae pv. oryzae.
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摘要  

由稻黄单胞菌稻致病变种Xanthomonas oryzae pv. oryzae (Xoo)引起水稻白叶枯是一种毁灭性的细菌性病害降低水稻产量并导致重大经济损失。细菌sigma (σ)因子是一类非专一性的蛋白,它能够与RNA聚合酶结合并识别特定的启动子,σ70因子还参与调节应激反应和毒力的基因的表达。然而,σ70因子RpoDXoo中的功能及其调控机制尚不清楚。在本研究中,我们通过生物信息学分析发现RpoD在植物病原菌尤其是在黄单胞菌中是相当保守的。生长曲线和致病性检测结果表明PXO_RpoD敲除后Xoo的生长无明显影响但对水稻的致病性显著降低为进一步鉴定受PXO_RpoD直接调控的基因,我们在野生型PXO_RpoD C端融合了Flag标签,并进行了靶标下切割和标记CUT&Tag分析。结合表型试验发现,PXO_RpoD参与调控Xoo的游动性和氧化胁迫响应。与野生型菌株相比,PXO_RpoD缺失突变体减弱了非寄主烟草的过敏反应,说明PXO_RpoD可能参与调控三型分泌系统。通过细菌单杂交和凝胶迁移试验结果表明PXO_RpoDhrpGhrpX的启动子直接互作。综上所述,本研究发现PXO_RpoD参与调节运动能力和氧化应激,是维持Xoo致病力所必需的基因。此外,PXO_RpoD能够直接与hrpGhrpX的启动子结合,从而调控三型分泌系统及效应子的表达。本研究阐明了PXO_RpoD在参与调控Xoo致病性中的作用,防治水稻白叶枯病潜在靶点的开发提供了理论依据



Abstract  

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice, which reduces crop yield and leads to significant economic losses.  Bacterial sigma (σ) factors are highly specialized proteins that allow RNA polymerase to recognize and bind to specific promoters.  σ70 factors also regulate the expression of genes involved in stress response and virulence.  However, the role of RpoD in Xoo is still unclear.  In this study, we found that σ70 factor RpoD is quite conservative among phytopathogenic bacteria, especially in Xanthomonas sp.  In Xoo, PXO_RpoD plays an important role in oxidative stress tolerance and cell motility, as well as being essential for full virulence.  Cleavage under targets and tagmentation (CUT&Tag) analyses indicated that RpoD mediates the type three secretion system (T3SS) by regulating the regulation of hrpG and hrpX.  By performing bacterial one-hybrid and electrophoretic mobility assay (EMSA), we observed that RpoD directly bound to the promoters of hrpG and hrpX.  Collectively, these results demonstrate the transcriptional mechanism and pathogenic functions of RpoD in regulating cell motility and oxidative stress response, providing novel insights into potential targets for disease control.

Keywords:  Oryza sativa        sigma factor        pathogenicity        transcriptional regulation        type III secretion system  
Received: 21 July 2023   Online: 18 October 2023   Accepted: 11 September 2023
Fund: This work was supported by the National Natural Science Foundation of China (32072379, 32001865 and 32202259).  
About author:  Zhizhou Xu, E-mail: myzhizhou@163.com; #Correspondence Fengquan Liu, Tel: +86-25-84390277, E-mail: fqliu20011@sina.com

Cite this article: 

Zhizhou Xu, Guichun Wu, Bo Wang, Baodian Guo, Cong Sheng, Yangyang Zhao, Bao Tang, Yancun Zhao, Fengquan Liu. 2025. Sigma factor 70 RpoD contributes to virulence by regulating cell motility, oxidative stress tolerance, and manipulating the expression of hrpG and hrpX in Xanthomonas oryzae pv. oryzae. Journal of Integrative Agriculture, 24(5): 1844-1859.

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