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欧美杨溃疡病是由Lonsdalea quercina(原称Brenneria quercina,Erwinia quercina)引起的一种细菌性病害,2005年首次在我国河南发现,对我国杨树产业造成了严重影响。菌株N-5-1是从河南濮阳自然发病杨树枝条上分离到的致病菌株。根据N-5-1菌株全基因组测序的初步结果分析,发现N-5-1具有完整的III型分泌系统(Type III secretion system,T3SS)。该系统与植物病原菌Erwinia amylovora CFBP1430和Dickeya dadantii 3937的T3SS高度相似,共由26个基因编码,共约23kb,其中9个为保守的hrc基因。将L.quercina N-5-1菌株T3SS中保守的结构基因hrc V进行缺失突变,生物测定发现Δhrc V突变体对“中林46杨”(Populus×euramericana‘Zhonglin 46’)2年生枝条的致病力明显下降,而互补菌株HBhrc V致病力与野生菌株保持一致。表明该菌中T3SS是病原细菌重要的致病性因子。菌株N-5-1中hrc V基因的突变导致诱导烟草过敏性坏死反应能力丧失,但并没有影响菌株的生长速率、游动性和生物膜的形成。本研究首次证明了L.quercina N-5-1菌株的T3SS是重要的致病因子。
Occidental ulcer disease is a bacterial disease caused by Lonsdalea quercina (formerly Brenneria quercina, Erwinia quercina). It was first discovered in Henan of China in 2005 and has seriously affected the poplar industry in our country. Strain N-5-1 is a pathogenic strain isolated from poplar branches of natural disease in Puyang, Henan Province. Based on the preliminary results of genome-wide sequencing of N-5-1 strain, N-5-1 was found to have a complete Type III secretion system (T3SS). This system is highly similar to the T3SS of the plant pathogens Erwinia amylovora CFBP1430 and Dickeya dadantii 3937, and encodes a total of 26 genes with a total of about 23 kb, of which 9 are conserved hrc genes. The mutation of hrc V, a conserved structural gene in T3SS of L.quercina N-5-1 strain, was mutated and bioassay found that the Δhrc V mutant had no significant effect on 2-year-old shoots of "Populus × euramericana’Zhonglin 46 ’ The virulence of HBhrc V in the complementary strain was consistent with that of the wild strain. It is indicated that T3SS in this bacterium is an important virulence factor of pathogenic bacteria. The mutation of hrc V gene in strain N-5-1 led to the loss of ability to induce allergic necrosis of tobacco, but did not affect the growth rate, mobility and biofilm formation of the strain. This study demonstrated for the first time that T3SS of L.quercina N-5-1 strain is an important causative agent.