2014年中国不同地区对虾白斑综合征病毒ORF14/15和ORF23/24缺失区序列比较

Comparison of the Missing Sequences of ORF14/15 and ORF23/24 of WSSV from Different Regions of China in 2014

中文关键词: WSSV  ORF14/15  ORF23/24  序列分析

英文关键词: WSSV  ORF14/15  ORF23/24  Sequence analysis

中文摘要:

      对虾养殖面临诸多病害威胁，对虾白斑综合征病毒(White spot syndrome virus, WSSV)是养殖对虾主要病原之一，WSSV不同地理株的变异可能导致WSSV毒力的变化。为了解2014年中国大部分地区WSSV ORF14/15和ORF23/24的变异情况，本研究选择2014年1月–8月期间采集的48份WSSV阳性样本，用特异引物扩增ORF14/15和ORF23/24片段，连接于T载体，转化至Top10中，筛选阳性克隆，测序分析不同样本之间的缺失差异。结果显示，能够扩增ORF14/15和ORF23/24样品的比例分别为43.75%和33.33%。在ORF14/15扩增中，分别扩增出1260 bp、1270 bp、1892 bp和2662 bp片段，与TH-96-Ⅱ比对共有4种缺失情况，即缺失6540 bp、6530 bp、5908 bp和5138 bp。而在ORF23/24扩增中，分别扩增出1140 bp和1146 bp片段，与中国台湾株(TW)比对有两种缺失情况，即缺失12070 bp和12064 bp。研究结果表明，WSSV在中国大部分地区存在一定程度的变异，而不同毒株之间在ORF14/15可变区差异比较明显，在ORF23/24可变区差异不大，但均具有大片段缺失。

英文摘要:

      White spot syndrome virus (WSSV) is one of the major pathogens that severely harm shrimp aquaculture. Different strains of WSSV display various virulence. In order to understand the geographic variation in fragments ORF14/15 and ORF23/24 of WSSV in China, we collected 48 samples of WSSV-infected shrimp from disease outbreak areas in 7 provinces of China between January and August in 2014. We identified the genotypes of WSSV-positive samples using PCR with ORF14/15 and ORF23/24 specific primers, and the amplified fragments were conjugated into T-vectors and transformed into the Top10 cells. We selected the positive clones and obtained their sequences. Then we compared the missing fragments of ORF14/15 and ORF23/24 from different samples with the sequences of TH-96-Ⅱ and China Taiwan strain (TW, AF440570) respectively. There were 21 samples with the products of ORF14/15 amplification, and 16 samples with the products of ORF23/24 amplification. The amplification ratios of ORF14/15 and ORF23/24 were 43.75% and 33.33% respectively. There were only 4 types of ORF14/15 compared to TH-96-Ⅱ. The lengths of the amplified fragments were 1260 bp, 1270 bp, 1892 bp and 2662 bp, corresponding to the missing 6540 bp, 6530 bp, 5908 bp and 5138 bp respectively compared to TH-96-Ⅱ. There were two types of ORF23/24 compared to the TW strain. The lengths of the amplified fragments were 1140 bp and 1146 bp, corresponding to the missing 12070 bp and 12064 bp respectively compared to the TW strain. These results suggested a certain degree of prevalence and variation of WSSV in China. There was an obvious difference in ORF14/15 between different strains，but only a minimal difference in ORF23/24. It is most likely that the variation in the missing fragments correlates with divergent WSSV virulence in different regions, and this notion needs to be further tested.