Zhou X, Liu Y, Calvert L, Munoz C, Otim-Nape G W, Robinson D J, Harrison B D
Scottish Crop Research Institute, Invergowrie, Dundee, UK.
J Gen Virol. 1997 Aug;78 ( Pt 8):2101-11. doi: 10.1099/0022-1317-78-8-2101.
Geminivirus isolates associated with the epidemic of severe cassava mosaic disease in Uganda were studied and compared with virus isolates from the part of Uganda outside the epidemic area, and with African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV). Isolates of a novel type [the Uganda variant (UgV)] were detected in severely affected plants from the epidemic area, whereas those from plants outside the epidemic area were typical of ACMV. The complete nucleotide sequences of DNA-A of UgV (2799 nt) and of a Tanzanian isolate of EACMV (2801 nt) were determined and are extremely similar, except for the coat protein (CP) gene. The CP gene of UgV has three distinct regions: the 5' 219 nt are 99% identical to EACMV (only 79% to ACMV); the following 459 nt are 99% identical to ACMV (75% to EACMV); and the 3' 93 nt are 98% identical to EACMV (76% to ACMV). UgV DNA-A therefore is considered to have arisen by interspecific recombination of EACMV and ACMV. Despite the hybrid nature of their CP, UgV isolates were indistinguishable from ACMV in tests with 20 monoclonal antibodies (MAbs), including seven which reacted with ACMV but not EACMV. The discontinuous epitopes detected by these seven MAbs must involve amino acids which lie in the central part of the CP (residues 74-226) and which differ in ACMV and EACMV. UgV isolates were detected in severely mosaic-affected plants from all 11 widely separated locations sampled. The probable role of recombination in geminivirus evolution in the short to medium term is discussed.
对乌干达与严重木薯花叶病流行相关的双生病毒分离株进行了研究，并与来自乌干达流行区以外地区的病毒分离株、非洲木薯花叶病毒（ACMV）和东非木薯花叶病毒（EACMV）进行了比较。在流行区严重受影响的植株中检测到一种新型分离株[乌干达变种（UgV）]，而流行区以外植株的分离株则是典型的ACMV。测定了UgV（2799 nt）和EACMV坦桑尼亚分离株（2801 nt）的DNA-A完整核苷酸序列，除外壳蛋白（CP）基因外，二者极为相似。UgV的CP基因有三个不同区域：5'端219 nt与EACMV的同源性为99%（与ACMV仅为79%）；接下来的459 nt与ACMV的同源性为99%（与EACMV为75%）；3'端93 nt与EACMV的同源性为98%（与ACMV为76%）。因此，UgV DNA-A被认为是由EACMV和ACMV种间重组产生的。尽管UgV的CP具有杂种性质，但在使用20种单克隆抗体（MAb）进行的检测中，UgV分离株与ACMV无法区分，其中包括7种与ACMV反应但不与EACMV反应的单克隆抗体。这7种单克隆抗体检测到的不连续表位必定涉及CP中部（第74 - 226位氨基酸）的氨基酸，而这些氨基酸在ACMV和EACMV中有所不同。在从11个广泛分布的地点采集的严重花叶病植株中均检测到了UgV分离株。文中讨论了重组在双生病毒短期至中期进化中可能发挥的作用。
