五种常见伊朗绵羊囊尾线虫的内转录间隔区和基因间隔区的比较
Comparison of internal transcribed spacers and intergenic spacer regions of five common Iranian sheep bursate nematodes.
作者信息
Nabavi Reza, Conneely Brendan, McCarthy Elaine, Good Barbara, Shayan Parviz, DE Waal Theo
机构信息
Dept. of Pathobiology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran.
School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland ; Teagasc, Animal Production Research Centre, Athenry, Co Galway, Ireland.
出版信息
Iran J Parasitol. 2014 Sep;9(3):350-7.
BACKGROUND
Accurate identification of sheep nematodes is a critical point in epidemiological studies and monitoring of drug resistance in flocks. However, due to a close morphological similarity between the eggs and larval stages of many of these nematodes, such identification is not a trivial task. There are a number of studies showing that molecular targets in ribosomal DNA (Internal transcribed spacer 1, 2 and Intergenic spacer) are suitable for accurate identification of sheep bursate nematodes. The objective of present study was to compare the ITS1, ITS2 and IGS regions of Iranian common bursate nematodes in order to choose best target for specific identification methods.
METHODS
The first and second internal transcribed spacers (ITS1and ITS2) and intergenic spacer (IGS) of the ribosomal DNA (rDNA) of 5 common Iranian bursate nematodes of sheep were sequenced. The sequences of some non-Iranian isolates were used for comparison in order to evaluate the variation in sequence homology between geographically different nematode populations.
RESULTS
Comparison of the ITS1 and ITS2 sequences of Iranian nematodes showed greatest similarity among Teladorsagia circumcincta and Marshallagia marshalli of 94% and 88%, respectively. While Trichostrongylus colubriformis and M. marshalli showed the highest homology (99%) in the IGS sequences. Comparison of the spacer sequences of Iranian with non-Iranian isolates showed significantly higher variation in Haemonchus contortus compared to the other species.
CONCLUSION
Both the ITS1 and ITS2 sequences are convenient targets to have species-specific identification of Iranian bursate nematodes. On the other hand the IGS region may be a less suitable molecular target.
背景
准确鉴定绵羊线虫是流行病学研究和羊群耐药性监测的关键环节。然而，由于许多此类线虫的虫卵和幼虫阶段在形态上极为相似，因此这种鉴定并非易事。有多项研究表明，核糖体DNA中的分子靶点（内部转录间隔区1、2和基因间隔区）适用于准确鉴定绵羊有囊尾线虫。本研究的目的是比较伊朗常见有囊尾线虫的ITS1、ITS2和IGS区域，以便为特定鉴定方法选择最佳靶点。
方法
对伊朗绵羊的5种常见有囊尾线虫的核糖体DNA（rDNA）的第一和第二内部转录间隔区（ITS1和ITS2）以及基因间隔区（IGS）进行测序。使用一些非伊朗分离株的序列进行比较，以评估地理上不同的线虫种群之间序列同源性的差异。
结果
伊朗线虫ITS1和ITS2序列的比较显示，环形泰勒虫和马歇尔马歇尔线虫之间的相似性最高，分别为94%和88%。而蛇形毛圆线虫和马歇尔马歇尔线虫在IGS序列中显示出最高的同源性（99%）。伊朗分离株与非伊朗分离株的间隔区序列比较显示，与其他物种相比，捻转血矛线虫的变异明显更高。
结论
ITS1和ITS2序列都是对伊朗有囊尾线虫进行物种特异性鉴定的便捷靶点。另一方面，IGS区域可能是不太合适的分子靶点。
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