【作者】 覃静；

【导师】 唐纪良； 何勇强；

【作者基本信息】 广西大学 ， 微生物， 2004， 硕士

【摘要】 对已完成全基因测序的两个野油菜黄单胞菌菌株Xcc 8004和Xcc ATCC33913的基因组结构进行分析，结果表明在编码蛋白水平上，两个基因组达97.5％的同源性，而在基因组大小、结构上存在一定差异。主要差异包括：(1)8004的基因组比33913大72，538bp；(2)基因组结构上存在一个大片段、两个小片段倒置重排，以及一个移位重排；(3)8004中有两个菌株特异基因岛(giX8-a、giX8-b)，33913有一个菌株特异基因岛(giX3-a)；(4)8004在白萝卜白沙南畔洲晚萝卜栽培种上的相对致病力比33913高。 以8004及33913基因组结构为参照，采用PCR及Southern blotting方法对20株中国不同地域Xcc分离菌株的基因组进行分析，结果表明所有菌株基因组里都含有与Xcc 8004和33913相似的致病相关基因簇(gum、hrp、LPS、type Ⅱ secretory system)。而在基因组结构上，不同地域分离株与8004或33913都存在一定差异，所有中国菌株都未检测出对应的8004-33913染色体重排接口，也没有giX8-b和giX3-a基因岛，只有3株中国菌株(1号、3号和11号)含有与giX8-a相似的基因岛结构。主要表型检测表明，菌株间在EPS产量和致病力等方面均存在较大差异，这些表型与基因岛的存在没有明显相关性。该研究结果提示野油菜黄单胞菌在基因组结构进化方面存在较大的可塑性，而在致病相关基因簇方面具有一定的保守性。更多还原

【Abstract】 Genomic comparison of two Xanthomonas campestris pv. campestris (Xcc) strains, Xcc 8004 and Xcc ATCC33913, revealed that the two Xcc strains share 97.5% amino acid homology, whereas they might undergo large genomic reorganization during their evolution. The main discrepancies include: (1) The genome size of Xcc 8004 is 72,538bp larger than that of Xcc 33913; (2) The inverted rearrangement of a large segment and two smaller segments, and a translocated fragment were identified; (3) There are two strain specific genomic islands, designated as giX8-a and giX8-b, respectively in Xcc 8004 and one specific genomic islands in Xcc 33913, named giX3-a; (4) Xcc 8004 is more virulent than Xcc 33913 on a certain cultivar of radish, the Baisha Nanbanzhou.The genomic differences in different geographical isolates were analyzed by using PCR and Southern blotting. The results revealed that all of the Xcc isolates harbor the similar pathogenic clusters, such as gum?hrp?LPS?type II secretory system cluster, same as that in Xcc 8004 and 33913. The patterns of genomic rearrangements found betweengenomes of 8004 and 33913, were not identified in genomes of all Chinese isolates. The strains specific genomic islands giX8-a, giX8-b and giX3-a were found absent in all the genomes of the Chinese, but the three Chinese isolates, No.l, No.3 and No.11 were found containing the giX8-a.The phenotypic analysis showed that the Xcc strains differ significantly in EPS production and pathogenicity. This study demonstrated that the genomic structure in Xcc strains is in its high plasticity during their evolution, but it is conserved in the clusters related to pathogenicity.更多还原