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

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.