欧美杨细菌性溃疡病菌双组份系统反应调节基因LqRR2的功能研究

Functional analysis of Orphan LqRR2 gene in Lonsdalea quercina subsp.populi

由Lonsdalea quercina subsp.populi引起的欧美杨溃疡病于2006年在国内首次发现,不同于其它病原菌造成的杨树溃疡病,该病害对欧美杨速生林的生长造成毁灭性破坏,已造成了严重的经济损失,该病原菌的致病分子机制尚不清楚。双组分系统是细菌重要的信号传递通路,在细菌的生长繁殖、逆境胁迫应答、环境适应以及病原菌致病过程中发挥重要作用。开展双组份系统研究将有助于解析欧美杨细菌性溃疡病菌的致病机制。本研究鉴定了欧美杨细菌性溃疡病菌L.quercina双组份孤儿反应调节基因LqRR2,并对其生物学功能进行了研究。通过同源重组获得了LqRR2基因的缺失突变体△LqRR2。表型测定结果显示,与野生型菌株相比,突变体△LqRR2在半固体培养基上的游动能力显著减弱,对欧美杨‘107杨’枝干的毒性也显著降低。但是,突变体的生长速率、生物膜形成能力以及胞外多糖产量较野生型无显著差别。此外,荧光定量PCR分析结果显示,游动性相关基因flg B、flg C和flg E的表达量在突变体中明显降低。综上所述,双组份调节蛋白编码基因LqRR2是欧美杨细菌性溃疡病菌L.quercina维持病原菌游动性和全毒性所必需的。

A bacterial canker disease of Populus × euramericana caused by Lonsdalea quercina subsp.populi was first discovered in China in 2006.The disease has caused devastating damage and severely economic loss to poplar plants,but relatively little is known about its pathogenic mechanism.Two-component systems （TCS） in bacteria are important signaling pathways responsible for the regulation of growth,reproduction,stress response,environmental adaptation and virulence expression.Researches on TCS will help us better understand the regulation mechanism of virulence in L.quercina.In this study,we identified and functionally characterized an orphan response regulator-coding gene LqRR2.The LqRR2 deletion mutant （△LqRR2） was generated by homologous recombination.In comparison with the wild-type strain N-5-1,the swimming ability and the virulence on poplar cv.107 of the mutant △LqRR2 were significantly decreased.LqRR2 deletion didn＇t affect the growth rate,biofilm formation and extracellular polysaccharide production.In addition,qRT-PCR analysis showed that the expression levels of three genes associated with bacterial motility （flgB,flgC and flgE） were significantly decreased in the mutant strain.Taken together,the orphan response regulator gene LqRR2 is required for motility and full virulence of L.quercina.