Novel Insights into Tat Pathway in Xanthomonas oryzae pv. oryzae Stress Adaption and Virulence: Identification and Characterization of Tat-Dependent Translocation Proteins.

Xanthomonas oryzae pv. oryzae, an economically important bacterium, causes a serious disease in rice production worldwide called bacterial leaf blight. How X. oryzae pv. oryzae infects rice and causes symptoms remains incompletely understood. Our earlier works demonstrated that the twin-arginine translocation (Tat) pathway plays an vital role in X. oryzae pv. oryzae fitness and virulence but the underlying mechanism is unknown. In this study, we used strain PXO99 as a working model, and identified 15 potential Tat-dependent translocation proteins (TDTP) by using comparative proteomics and bioinformatics analyses. Combining systematic mutagenesis, phenotypic characterization, and gene expression, we found that multiple TDTP play key roles in X. oryzae pv. oryzae adaption or virulence. In particular, four TDTP (PXO_02203, PXO_03477, PXO_02523, and PXO_02951) were involved in virulence, three TDTP (PXO_02203, PXO_03477, and PXO_02523) contributed to colonization in planta, one TDTP (PXO_02671) had a key role in attachment to leaf surface, four TDTP (PXO_02523, PXO_02951, PXO_03132, and PXO_03841) were involved in tolerance to multiple stresses, and two TDTP (PXO_02523 and PXO_02671) were required for full swarming motility. These findings suggest that multiple TDTP may have differential contributions to involvement of the Tat pathway in X. oryzae pv. oryzae adaption, physiology, and pathogenicity.