水稻白叶枯病菌Δrpfxoo基因缺失突变体DSF信号产生和毒性表达

Diffusible signal factor production and virulence expression in ΔrpfFxoo,ΔrpfCxoo and ΔrpfGxoo,the gene deletion mutants of DSF/Rpf signaling proteins of Xanthomonas oryzae pv. oryzae

【目的】旨在阐明3个DSF/Rpfxoo信号系统成员RpfFxoo、RpfCxoo和RpfGxoo在水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)毒性表达中的功能。【方法】用标记置换法缺失突变rpfFxoo、rpfCxoo和rpfGxoo基因,测定突变体及其互补菌株的DSF(diffusible signal factor)信号分子产生、胞外多糖(EPS)产生及其对水稻的致病性。【结果】从野生型菌株PXO99A基因组中克隆了推测与DSF信号生成和传导有关的基因rpfFxoo、rpfCxoo和rpfGxoo,获得了相应的单基因或双基因缺失突变体。与PXO99A产生DSF相比,ΔrpfFxoo、ΔrpfF+Cxoo和ΔrpfF+Gxoo均不产生DSF,ΔrpfCxoo过量产生,ΔrpfGxoo产量降低;rpfFxoo、rpfCxoo和rpfGxoo可以分别互补Xoo和Xcc的相应基因突变体,恢复DSF产生表型。除ΔrpfFxoo的EPS产生无明显变化外,其余突变体的均显著减少。所有突变体对水稻的致病性均显著下降。【结论】RpfFxoo、RpfCxoo和RpfGxoo调控了Xoo的DSF信号生成、EPS产生和致病性。

【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】Δrpfxoo,the gene deletion mutants were generated from PXO99A,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 PXO99A and the relative single or double mutants were constructed. Compared to PXO99A,DSF production was deficient in ΔrpfFxoo,ΔrpfFCxoo and ΔrpfFGxoo,while DSF was overproduced in ΔrpfCxoo and reduced in ΔrpfGxoo. DSF production of ΔrpfFxcc,ΔrpfCxcc and ΔrpfGxcc,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 ΔrpfFxoo were remarkably deficient in production of extracellular polysaccharide. All the mutants significantly exhibited the reduced bacterial virulence to rice. 【Conclusion】DSF signaling proteins RpfFxoo、RpfCxoo and RpfGxoo might function in regulation of DSF biogenesis and EPS production and bacterial virulence.