Environmental and Genetic Regulation of Type III Secretion System and Pathogenicity in Pseudomonas syringae pv. actinidiae by TetR/AcrR Transcription Factor C_22735 and its Key modulator RetS

ABSTRACT: Kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) is the emerging global concern for kiwifruit production. The successful infection of Psa in kiwifruit relies on the type III secretion system (T3SS), and its regulatory pathway is modulated by hrpR/S-L. However, the mechanisms by which certain transcriptional factors regulate this pathway remain less understood. In this study, we have identified the TetR/AcrR family transcription factor (TF) C_22735 in the Psa3-M228 strain through both Tn libraries and DNA pull-down strategy. The genetic mutation in TF C_Δ22735 exhibited a significantly decreased pathogenicity, and showed diminished ability to induce a hrpR/S/L and hrpA expression in kiwifruit leaves, and twigs, as well as reduced hypersensitive response (HR) in Nicotiana benthamiana. Similarly, another gene C_04700 knockout strain capacity to induce tobacco HR, and its pathogenicity to kiwifruit leaf discs was also significantly reduced. Moreover, the considerable overlap in down-regulated genes between Δ22735 and Δ4700 mutants highlights the intertwined regulatory roles of C_22735 and C_04700, and it suggests a tightly coordinated regulatory system, where C_04700 may serve as a primary signal sensor and C_22735 as a downstream transcriptional activator. In addition, Transcriptomic studies and, electrophoretic mobility shift assays (EMSA), and fluorescence detection indicated that C_22735 not only positively regulates T3SS but also directly binds to the upstream untranslated regions of hrpR/S and hrpL to modulate T3SS activity. This is the first study revealing the insights into TF C_22735 regulating virulence of Psa, which additively require TCS. This study adds up a novel pathway of T3SS regulation and provide the foundation for further research.

ORGANISM(S): Pseudomonas syringae pv. actinidiae

PROVIDER: GSE286487 | GEO | 2025/01/31

REPOSITORIES: GEO