植物寄生线虫分支酸变位酶基因的研究进展

Progress on chorismate mutase gene of plant parasitic nematodes

植物寄生线虫食道腺中表达的寄生基因编码的分泌蛋白在线虫侵入寄主植物、建立取食位点和抑制寄主的防御反应过程中起重要作用。利用植物寄生线虫食道腺削减cDNA文库及基于同源克隆等方法,鉴定了这些过程中起作用的分支酸变位酶(CM)基因。带有氨基酸末端信号肽的根结线虫CM、孢囊线虫CM与细菌CM的蛋白质序列非常相似。mRNA原位杂交表明,CM基因专门存在于植物寄生线虫的亚腹食道腺中。RT-PCR分析表明,它们的转录丰度在线虫寄生的早期丰度较高,在后期较低或者难以检测到。Southern杂交表明,这些CM基因为多基因家族。CM的蛋白质在专性内寄生线虫中广泛存在,表明这种多功能的酶在控制线虫侵染植物的过程中起重要作用。

Parasitism genes encoding secretory proteins expressed in oesophageal glands of plant parasitic nematodes play critical roles in invasion, establishment of feeding sites and suppression of host defenses. Seve-ral chorismate mutase （CM） genes have been isolated and identified from Meloidogyne incognita and M. javanica oesophageal gland-region cDNA library and from homology-based cDNA cloning of M. arenaria. These chorismate mutases with amino-terminal signal peptides are significantly similar to that of Globodera pallida, Heterodera glycines and bacteria. In-situ mRNA hybridization showed that the transcripts of CM accumulate specifically in the two subventral oesophageal gland cells of Meloidogyne species. RT-PCR analysis confirmed that their transcript abundances were high in the early parasitic juvenile stages, and low or undetec-table in later parasitic stages of the nematode. Southern blot analysis revealed that these CM genes were members of a small multigene family in plant parasitic nematodes. The widespread presence of CMs in specialized se-dentary endoparasitic nematode species suggests that this multifunctional enzyme may be a key factor in modulating plant parasitism.