Strain of Xanthomonas oryzae pv. oryzae Loses Virulence through Dysregulation of Cardiolipin Synthase

Small non-coding RNAs (sRNAs) are pivotal post-transcriptional regulatory factors influencing biological activity. Studies on the rice bacterial blight pathogen <i>Xanthomonas oryzae</i> pathovar <i>oryzae</i> strain PXO99^A, previously identified a virulence-associated sRNA, trans3287. A mutant strain lacking this sRNA, named SK01, resulted in markedly diminished virulence towards rice. This study aims to further elucidate the underlying bacterial virulent function of trans3287. The expression of trans3287 was quantified in virulence-inducing and standard nutritional conditions to clarify its production mechanism. The detection of virulence-associated genes revealed that trans3287 regulated the synthesis processes of extracellular polysaccharides, lipopolysaccharides, and the type III secretion system. Moreover, bioinformatics prediction and quantitative PCR indicated a potential direct target of trans3287, <i>PXO_03470</i>, encoding cardiolipin synthase. A dual-plasmid system fusing with GFP tag and protein immunoblotting confirmed that sRNA trans3287 negatively regulated <i>PXO_03470</i>. Bacterial biofilms demonstrated trans3287 regulated the disruption of biofilm integrity through cardiolipin synthase. This study provides preliminary insights into the mechanistic underpinnings of the role of sRNA trans3287 in mediating bacterial virulence through cardiolipin synthase.