蔗糖水解酶注释基因XC0805与野油菜黄单胞菌8004菌株的蔗糖利用及致病相关

 野油菜黄单胞菌(Xanthomonas campestris pv.campestris,Xcc)是造成十字花科植物减产的重要病原菌,其通过水孔或伤口进入植物体内并在维管束中快速繁殖。光合产物(蔗糖)的运输主要依靠植物维管组织,同时蔗糖也是维管组织重要的能量来源。本研究利用生物信息学和遗传学等方法对Xcc中参与蔗糖利用的基因进行了分析,并研究了这些基因与其致病力的关系。Xcc 8004菌株中注释的参与蔗糖分解蛋白的编码基因有XC1002、XC1642、 XC1645和XC0805。 XC1002和XC1642的编码产物属于糖苷水解酶GH97蛋白超家族,而XC1645和XC0805的编码产物则属于GH13家族。突变分析发现除XC0805外,其他3个都不影响Xcc的蔗糖利用能力。接种实验表明,XC0805参与Xcc的侵染或在植物体内的生长,其他3个不参与致病过程。另外,Xcc 8004中预测参与蔗糖转运的基因(XC0806和XC0807)突变并不影响细菌的蔗糖利用和致病力,表明其可能存在其他的蔗糖转运通路。上述结果说明XC0805可能是Xcc 8004主要的蔗糖水解酶基因,且在致病中起重要作用。

The annotated sucrose hydrolase gene XC0805 is involved in sucrose utilization and virulence of Xanthomonas campestris pv.campestris

Xanthomonas campestris pv.campestris (Xcc) is the causal agent of black rot of Brassicaceae.It naturally enters xylem vessels through wounds or hydathodes and multiplies in the xylem.Transport of the photosynthetic product sucrose from source to sink largely depends on vascular tissues.Sucrose is also the major energy supplier for sink as well as vascular cells.Here,we systematically analyzed putative genes involved in sucrose hydrolysis and transport.Four proteinscoding genes (XC0805,XC1002,XC1642 and XC1645) are putatively involved in sucrose hydrolysis in Xcc 8004.The predicated products of XC1002 and XC1642 belong to glycoside hydrolase family 97 (GH97),and those of XC1645 and XC0805 are GH13 members.Among these four gene mutants,only XC0805 mutant had reduced ability on sucrose utilization compared with the wild-type strain.Moreover,only XC0805 mutation resulted in decreased virulence while other three mutants were similar to the wild-type strain.Furthermore,mutations of putative sucrose transporter genes (XC0806 and XC0807) did not alter the sucrose utilization and virulence of Xcc 8004,suggesting that there are other sucrose transport systems in Xcc 8004 other than ATCC 33913.Our results highlight that XC0805 is involved in sucrose utilization and virulence of Xcc 8004.