番茄黄化曲叶病毒自然种群的分子变异和进化研究

研究目的：创新要点：研究方法：重要结论：2006年我国上海首次发现番茄黄化曲叶病毒（TYLCV），随后TYLCV迅速蔓延至全国13个省份和自治区。本研究分析了2006至2010年期间TYLCV在我国首发地上海市的分子变异规律。本研究持续五年追踪田间TYLCV，分析TYLCV的全长基因组序列、分子变异及种群遗传结构，为防控TYLCV提供理论依据。2006至2010年从上海采集了26个TYLCV的分离物，利用高保真性的滚环扩增技术获得TYLCV分离物的全长基因组。应用MEGA5等生物信息学软件分析TYLCV的分子变异。TYLCV自然种群具有与RNA病毒相似的突变率，以基因间隔区的分子变异最大，平均突变率为4．81×10-3（见图2和表2）。TYLCV的大部分基因都处于负向选择，但包含在c1开放阅读框内的C4，却与c1承受着不同的选择压而处于正向选择（见图3和表6）。

Molecular variability and evolution of a natural population of tomato yellow leaf curl virus in Shanghai,China

Tomato yellow leaf curl virus （TYLCV）, belonging to the genus Begomovirus of the family Geminiviridae, is emerging as the most destructive pathogen of tomato plants. Since the first report of TYLCV in Shanghai, China in 2006, TYLCV has spread rapidly to 13 provinces or autonomous regions of China. In this study, the molecular varia- bility and evolution of TYLCV were monitored in Shanghai from its first upsurge in 2006 until 2010. Full-length genomic sequences of 26 isolates were obtained by rolling circle amplification. Sequence analysis showed that the intergenic region was the most variable, with a mean mutation rate of 4.81×10-3 nucleotide substitutions per site per year. Ge- netic differentiation was found within isolates obtained from 2006, 2009, and 2010, though a linear increase in genetic diversity over time was not evident. Whilst significant parts of TYLCV genes were under negative selection, the C4 gene embedded entirely within the C1 gene had a tendency to undergo positive selection. Our results indicate that a mechanism of independent evolution of overlapping regions could apply to the natural population of TYLCV in Shanghai, China.