Characterization of a putative endoxylanase in the migratory plant-parasitic nematode Radopholus similis
Characterization of a putative endoxylanase in the migratory plant-parasitic nematode Radopholus similis
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DOI：
10.1111/j.1364-3703.2009.00539.x
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发表时间：
2009-05-01
影响因子：
4.9
通讯作者：
Gheysen, Godelieve
中科院分区：
文献类型：
--
作者：
Haegeman, Annelies;Vanholme, Bartel;Gheysen, Godelieve
植物寄生线虫已经开发出一系列酶来降解坚硬的植物细胞壁。在这篇文章中，我们报道了一种推测的内寄生线虫相似Radopholus存在的内木聚糖酶。这种酶被认为能促进线虫的迁移，因为它能分解半纤维素的主要成分木聚糖。克隆出相应的基因Rs-xyl1，序列显示3个小内含子。有趣的是，所有三个内含子的位置都保守于来自Meloidogyne hapla的一个推定的内木聚糖酶中，而一个内含子的位置在来自Meloidogyne incognita的两个内木聚糖酶中保守，这表明它们是共同的祖先基因。采用原位杂交和半定量逆转录聚合酶链反应检测Rs-xyl1基因的时空表达。假定的蛋白质由一个信号肽、一个催化结构域和一个碳水化合物结合模块（CBM）组成。催化结构域与糖基水解酶家族5 （GHF5）和GHF30酶相似。利用隐马尔可夫模型和系统发育分析，我们能够证明Rs-XYL1及其最接近的同源物不是GHF5的成员，正如之前所建议的那样，而是在GHF30中形成一个子类。通过双链RNA靶向CBM区域沉默假定的内木聚糖酶，导致感染平均减少60%，表明该基因对线虫完成其生命周期很重要。
Plant-parasitic nematodes have developed an arsenal of enzymes to degrade the rigid plant cell wall. In this article, we report the presence of a putative endoxylanase in the migratory endoparasitic nematode Radopholus similis. This enzyme is thought to facilitate the migration of the nematode, as it breaks down xylan, the major component of hemicellulose. The corresponding gene (Rs-xyl1) was cloned and the sequence revealed three small introns. Interestingly, the position of all three introns was conserved in a putative endoxylanase from Meloidogyne hapla, and the position of one intron was conserved in two endoxylanases from Meloidogyne incognita, which suggests a common ancestral gene. The spatial and temporal expression of the Rs-xyl1 gene was examined by in situ hybridization and semi-quantitative reverse transcriptase-polymerase chain reaction. The putative protein consists of a signal peptide, a catalytic domain and a carbohydrate-binding module (CBM). The catalytic domain showed similarity to both glycosyl hydrolase family 5 (GHF5) and GHF30 enzymes. Using Hidden Markov Model profiles and phylogenetic analysis, we were able to show that Rs-XYL1 and its closest homologues are not members of GHF5, as suggested previously, but rather form a subclass within GHF30. Silencing the putative endoxylanase by double-stranded RNA targeting of the CBM region resulted in an average decrease in infection of 60%, indicating that the gene is important for the nematode to complete its life cycle.