[Diffusible signal factor production and virulence expression in deltarpfFxoo, deltarpfCxoo and deltarpfGxoo, the gene deletion mutants of DSF/Rpf signaling proteins of Xanthomonas oryzae pv. oryzae].

Objective: To better elucidate the functions of RpfFxoo, RpfCxoo and RpfGxoo, 3 proteins of diffusible signal factor (DSF)-dependent cell-cell signaling system in regulation of virulence expression of Xanthomonas oryzae pv. oryzae (Xoo).

Method: Deltarpfxoo, the gene deletion mutants were generated from PXO99(A), the wild-type strain of Xoo via marker-exchanging and DSF biosynthesis and extracellular polysaccharide production and virulence to rice of the mutants were assayed.

Result: rpfFxoo,rpfCxoo and rpfGxoo were cloned from the genomic DNA of PXO99(A) and the relative single or double mutants were constructed. Compared to PXO99(A), DSF production was deficient in deltarpfFxoo, deltarpfFCxoo and deltarpfFGxoo, while DSF was overproduced in deltarpfCxoo and reduced in deltarpfGxoo. DSF production of deltarpfFxcc, deltarpfCxcc and deltarpfGxcc, the mutants of X. campestris pv. campestris can be restored as XC1, the wild-type strain by in trans complementation of rpfFxoo, rpfCxoo and rpfGxoo. All the mutants except deltarpfFxoo were remarkably deficient in production All the mutants significantly exhibited the reduced bacterial virulence to rice. of extracellular polysaccharide.

Conclusion: DSF signaling proteins RpfFxoo, RpfCxoo and RpfGxoo might function in regulation of DSF biogenesis and EPS production and bacterial virulence.