摘 要 ：为明确中国番茄黄化曲叶病毒(Tomato yellow leaf curl China virus, TYLCCNV)伴随的卫星DNAβ分子在寄主体内的遗传结构特点及种群变异水平,将TYLCCNV分离物Y10(Y10)和伴随的DNAβ(Y10β)的全长侵染性克隆经农杆菌介导共同接种心叶烟,从Y10β的分子克隆出发,对心叶烟中Y10β的种群结构、变异水平、突变分布及碱基变异类型进行分析。结果表明,Y10β种群具有丰富的遗传多样性及较高的变异水平,所获得的43个Y10β全长克隆在核苷酸水平均发生不同程度的变异,接种后60天的Y10β种群60-1和种群60-2的突变频率分别为2.7×10-3和3.0×10-3,另一个接种后120天的种群120-1的突变频率为3.0×10-3;此卫星DNAβ的变异位点在整个基因组内均有分布,但在A-rich区碱基变异位点数最多,且主要为碱基A的缺失和插入,特别是在889～901核苷酸位点,所得43个克隆中有19个克隆在这一区段发生碱基A的缺失或插入;此外,Y10β的碱基替换突变类型以A突变为G及T突变为C的比例较高。
Abstract:To identify the genetic structure and population variation of satellite DNAβ associated with Tomato yellow leaf curl China virus (TYLCCNV), the full length infectious clones of DNA-A (Y10) and DNAβ (Y10β) of TYLCCNV Y10 isolate were used to inoculate Nicotiana glutinosa plants mediated by agrobacterium. The full length of Y10β in the plants were cloned and sequenced, and they were analyzed for population structure, variation level, mutation distribution and nucleic acid mutation types. The results demonstrated that the populations of Y10β had abundant genetic diversity and high level of mutations. From 43 sequenced full length clones of Y10β, all of them had different degree of mutations in nucleotide level. For the populations of Y10β 60-1 and 60-2 at 60 days post inoculation (dpi), the mutation frequency were 2.7×10-3 and 3.0×10-3 respectively. For another population 120-1 at 120 dpi, the mutation frequency was 3.0×10-3. The mutations were distributed throughout the whole genome sequence of Y10β, strikingly, lots of mutation sites were found in A-rich region in which the most types of mutations were deletion or insertion of base A. Deletion or insertion of A occurred in 19 out of 43 clones in the region from 889 to 901 nucleotides. The base transitions from A to G or from T to C were quite frequent in the mutation types of Y10β populations.