A critical role of sux cistron-mediated sucrose uptake for virulence of the rice blight pathogen Xanthomonas oryzae pv. oryzae

To date, the role of SWEET-released sucrose for virulence remains unclear. We here identified the sux locus of Xoo , consisting of a LacI-type repressor (SuxR), an outer membrane TonB-like porin (SuxA), an inner membrane MFS H+-symporter (SuxC), and a cytosolic sucrose hydrolase (SuxB).

Structural and functional analyses demonstrate that SuxB has exclusive sucrose hydrolase activity. Mutant analyses show that the transporter SuxC and the sucrose hydrolase are necessary for growth of bacteria on sucrose, while SuxA is not essential, likely due to the ability of other porins to transport sucrose across the outer membrane. Consistent with a role of SuxR as a sucrose repressor, transcriptome studies show sucrose-dependent regulation of the suxA/suxB genes.