Fu Hui-Chuan, Hu Jer-Ming, Hung Ting-Hsuan, Su Hong-Ji, Yeh Hsin-Hung
Department of Plant Pathology and Microbiology, College of Agriculture, National Taiwan University, 1 Sec. 4 Roosevelt Road, Taipei, Taiwan.
Phytopathology. 2009 Jul;99(7):812-22. doi: 10.1094/PHYTO-99-7-0812.
Banana bunchy top virus (BBTV) can be transmitted by aphids and consists of at least six integral components (DNA-R, -U3, -S, -M, -C, and -N). Several additional replication-competent components (additional Reps) are associated with some BBTV isolates. A collected BBTV strain (TW3) that causes mild symptoms was selected to study the processes in BBTV evolution. Southern blot hybridization, polymerase chain reaction (PCR), and real-time PCR did not detect DNA-N in TW3. Real-time PCR quantification of BBTV components revealed that, except for the copy number of TW3 DNA-U3, each detected integral component of BBTV TW3 was at least two orders lower than that of the severe strains. No infection was observed in plants inoculated with aphids, which were first given acquisition access to the TW3-infected banana leaves. Recombination analysis revealed recombination between the integral component TW3 DNA-U3 and the additional Rep DNA-Y. All BBTV integral components contain a replication initiation region (stem-loop common region) that share high sequence identity. Sequence alignment revealed that TW3 DNA-R, -S, -M, and -C all have a stem-loop common region containing a characteristic 9-nucleotide deletion found only in all reported DNA-N. Our data suggest that the additional Rep DNAs can serve as sources of additional genetic diversity for integral BBTV components.
香蕉束顶病毒（BBTV）可通过蚜虫传播，由至少六个完整组分（DNA-R、-U3、-S、-M、-C和-N）组成。一些BBTV分离株还与几个具有复制能力的额外组分（额外Reps）相关。选择了一种引起轻微症状的收集到的BBTV毒株（TW3）来研究BBTV的进化过程。Southern印迹杂交、聚合酶链反应（PCR）和实时PCR在TW3中均未检测到DNA-N。对BBTV组分的实时PCR定量分析表明，除了TW3 DNA-U3的拷贝数外，检测到的BBTV TW3的每个完整组分均比严重毒株低至少两个数量级。在用蚜虫接种的植物中未观察到感染，这些蚜虫首先被给予获取感染TW3的香蕉叶的机会。重组分析显示完整组分TW3 DNA-U3与额外Rep DNA-Y之间发生了重组。所有BBTV完整组分都包含一个具有高度序列同一性的复制起始区域（茎环共同区域）。序列比对显示，TW3 DNA-R、-S、-M和-C都有一个茎环共同区域，该区域包含一个仅在所有已报道的DNA-N中发现的特征性9核苷酸缺失。我们的数据表明，额外的Rep DNA可以作为BBTV完整组分额外遗传多样性的来源。
