水稻细菌性条斑病菌REC结构域蛋白基因vemRXoc的功能鉴定

摘要

Xanthomonas oryzae pv.oryzicola（hereafter Xoc） is one of the major pathogenic bacteria of rice and causes bacterial leaf streak disease on rice resulting decline in yield and quality of rice production.The genome of Xoc GX01 strain contains an REC domain protein gene XOC2152 with 95.27% identity to the virulence gene vemR of Xanthomonas campestris pv.campestris（hereafter Xcc）.To identify the biological function of XOC2152 gene in Xoc,a non-polar mutant of XOC2152,named NK2152,was generated by suicide plasmid pK18mob mediated homologous integration.The exopolysaccharide production of NK2152 was 27.33% of that of the wild type GX01 and the swimming radius of NK2152 was 40.96% of that of GX01.The mutant was significant reduced in tolerance to copper ion compared to the wild type strain.Plant assay results showed that the lesion length on rice（Oryza sativa L.ssp.japonica cv.Nipponbare） leaves inoculated by needling with Xoc GX01 and NK2152 was respectively（3.86±1.19） cm and（0.98±0.45） cm at 10 days post inoculation.The intact CDS（coding sequence） of XOC2152 carried by pLAFR3 could complement the defects of XOC2152 mutant in phenotypes and virulence.This study demonstrated that the XOC2152 plays a similar role in Xoc to that of vemR gene in Xcc and was designated vemRXoc which is involved in the pathogenesis,exopolysaccharide production,motility,and copper ion tolerance of Xoc.%水稻细菌性条斑病菌（Xanthomonas oryzae pv.oryzicola,Xoc）是水稻的主要病原细菌之一,该菌引起的水稻细菌性条斑病可导致水稻减产、品质下降。Xoc GX01菌株基因组中含有一个与十字花科黑腐病菌（Xanthomonas campestris pv.campestris,Xcc）的致病相关基因vemR一致性高达95.27%的同源基因XOC2152,其编码蛋白中含有磷酸信号识别受体REC结构域。为了研究XOC2152基因在Xoc中的生物学功能,本研究通过基于自杀质粒pK18mob同源整合方法,构建了XOC2152的非极性突变体NK2152。该突变体的胞外多糖产量仅为野生菌株的27.33%,平板游动半径为野生菌株的40.96%,对铜离子耐受能力极显著降低。针刺接种水稻（日本晴品种）10d后,Xoc GX01处理的病斑平均长度为（3.86±1.19）cm,而突变体NK2152处理的病斑长度为（0.98±0.45）cm。带有该基因片段的pLAFR3可以互补突变体的表型和致病力变化。上述结果表明XOC2152基因具有与Xcc的vemR类似的功能,被命名为vemRXoc基因。本研究表明XOC2152基因（vemRXoc基因）与水稻细菌性条斑病菌的致病力、胞外多糖产量、运动能力以及对铜离子的耐性等相关。