从烟草上分离的中国番茄曲叶病毒及其卫星DNA全基因组结构特征

本研究从具有典型曲叶病症状的广西靖西烟草病植株上分离到病毒分离物JX-2，全基因组序列测定结果表明，JX-2DNA．A全长2738个核苷酸，共编码6个开放阅读框架（openreadingframes，ORFs），其中病毒链编码AV1（CP）和AV2两个ORFs，互补链编码AC1、AC2、AC3和AC4共4个ORFs。BLAST结果表明，JX-2DNA—A与中国番茄曲叶病毒（Tomato leaf curl Chinavirus，ToLCCNV）各分离物的相似性在93．0％-99．7％之间，其中与ToLCCNV广西番茄分离物ToLCCNV．G32的相似性最高，达99．7％，而与其它双生病毒的同源性均在88．0％以下，表明Jx-2是ToLCCNV的一个分离物。基于Jx-2和已报道的双生病毒属代表种DNA-A全基因组核苷酸序列构建的系统进化树显示，JX-2与ToLCCNV-G32分离物的亲缘关系最近，并与ToLCCNV其它分离物形成一个分支，而与其它10种双生病毒的亲缘关系均相对较远。利用双生病毒卫星DNAβ的特异性引物β01／β02在Jx-2样品中扩增到DNAβ分子（JX-2β），全长为1341个核苷酸，其互补链编码1个ORF（即βC1），并包含一个富含A序列和一个卫星病毒保守序列。序列分析表明，JX-2β与ToLCCNV伴随的DNAβ的相似性在91．0％～96．1％之间，其中与ToLCCNV-G61DNAβ和ToLCCNV—G18DNAβ的相似性最高（96．1％），与其它卫星DNAβ的相似性均低于61．8％。基于JX-2β全基因组核苷酸序列构建的系统进化关系树显示，JX-29与ToLCCNVG61分离物伴随的DNAβ亲缘关系最近，并形成一个独立的分支，再与ToLCCNV其余两个分离物伴随的DNAβ形成一个较大的分支。这是首次报道从烟草中分离到的中国番茄曲叶病毒及其伴随卫星DNA分子的全基因组结构特征。

Genomic Characterization of DNA-A and Associated Satellite DNA Molecule of an Isolate of Tomato leaf curl China virus Infecting Tobacco

Virus isolate JX-2 was isolated from tobacco showing typical leaf-curled symptoms in Jingxi county of Guangxi Province. The complete nucleotide sequence of JX 2 DNA-A was determined to be 2 738 nucleotides which encoded 6 open reading frames （ORFs） including two template strand-encoding ORFs （AV1 and AV2） and four anti-sense strand-encoding ORFs （AC1, AC2, AC3, and AC4）. The result of BLAST revealed that JX-2 DNA-A showed 93.0%-99.7% sequence identity with those isolates of Tomato leaf curl China virus （ToLCCNV） and shared the highest sequence identity （99.7%） with ToLCCNV isolate G32. Meanwhile less than 88.0% identity was shared with other begomoviruses, which indicated that virus isolate JX-2 infecting tobacco was one of ToLC- CNV isolates. Phylogenetic analysis of JX-2 and other reported begomoviruses DNA-A showed that JX-2 was the most closely related to ToLCCNV isolate G32 and clustered with other ToLCCNV isolates as a separate branch which was apart from other 10 kinds ofbegomoviruses. The fragment of satellite DNA molecule （JX-2β） was amplified with the primers β01 and β02 using JX-2 as template. JX 2β contained 1 341 nueleotides and encoded an ORF （βC1） by anti-sense strand. An adenine-rich region and a satellite conserved region （SCR） were also found in JX-2β. The sequence analysis indicated that JX-2β had 91.0%-96.1% sequence identity with the associated DNA β of ToLCCNV and shared the highest sequence identity with ToLCCNV-G61 DNAβ and ToLCCNV-G18 DNAβ（96.1%）, but got low sequence identity （less than 61.8%） with other reported satellite DNA molecules. Phylogenetic analysis indicated that JX-2β was the most closely related to ToLCCNV-G61 DNAβ and they clustered togeth er as a separate branch, and formed the main branch with other DNAβ associated with ToLCCNV. This was the first report ofgenomic characterization of ToLCCNV and its associated satellite DNA which isolated from tobacco .