al-Kaff N, Covey S N
Department of Virus Research, John Innes Centre, Norwich, U.K.
J Gen Virol. 1994 Nov;75 ( Pt 11):3137-45. doi: 10.1099/0022-1317-75-11-3137.
Infectious clones were prepared from virion DNA of three cauliflower mosaic virus (CaMV) isolates, 11/3, Xinjiang (XJ), and Aust, to investigate pathogenic variation in virus populations. Of 10 infectious clones obtained for isolate 11/3, four pathotypes were identified, each producing symptoms in turnip that differed from those of the 11/3 wild-type. Virus from two clonal groups of 11/3 was transmissible by aphids whereas that from two others was not. Of the five infectious clones obtained from isolate XJ, two groups were identified, one of which differed symptomatically from the wild-type. Only one infectious clone was obtained from isolate Aust and this had properties similar to the wild-type. Restriction enzyme polymorphisms were found in some clonal groups and these correlated with symptoms. Other groups with different pathogenic properties could not be distinguished apart by restriction site polymorphisms. Further variation was observed in the nucleotide sequences of gene II (coding for aphid transmission factor) from these viruses as compared with other CaMV isolates. In the aphid non-transmissible clones of isolate 11/3, one had a Gly to Arg mutation in gene II similar to that of other non-deleted non-transmissible CaMV isolates. The second had a 322 bp deletion at the site of a small direct repeat similar to that of isolate CM4-184 although occurring in a different position. The gene II deletion of isolate 11/3 produced a frame-shift that separated genes II and III by 60 bp. Most CaMV clones studied remained biologically stable producing similar symptoms during subsequent passages. However, one clone (11/3-7) produced two new biotypes during its first passage suggesting that it was relatively unstable. Our results show that wild-type populations of CaMV contain a range of infectious genome variants with contrasting biological properties and differing stability. We suggest that a variety of significant viral phenotypic changes can occur during each infection cycle resulting from relatively small genome changes.
为研究病毒群体中的致病性变异，从三种花椰菜花叶病毒（CaMV）分离株11/3、新疆株（XJ）和澳大利亚株的病毒粒子DNA制备了感染性克隆。对于分离株11/3获得的10个感染性克隆，鉴定出四种致病型，每种在芜菁中产生的症状都与11/3野生型不同。来自11/3两个克隆组的病毒可通过蚜虫传播，而另外两个克隆组的病毒则不能。从分离株XJ获得的五个感染性克隆中，鉴定出两个组，其中一组在症状上与野生型不同。从分离株澳大利亚株仅获得一个感染性克隆，其特性与野生型相似。在一些克隆组中发现了限制性内切酶多态性，这些多态性与症状相关。其他具有不同致病特性的组不能通过限制性位点多态性区分开来。与其他CaMV分离株相比，这些病毒的基因II（编码蚜虫传播因子）核苷酸序列中观察到进一步变异。在分离株11/3的蚜虫非传播性克隆中，一个在基因II中有甘氨酸到精氨酸的突变，类似于其他未缺失的非传播性CaMV分离株。第二个在一个小的直接重复序列位点有322 bp的缺失，类似于分离株CM4 - 184，尽管发生在不同位置。分离株11/3的基因II缺失产生了一个移码，使基因II和III相隔60 bp。大多数研究的CaMV克隆在随后的传代过程中保持生物学稳定性，产生相似的症状。然而，一个克隆（11/3 - 7）在其第一次传代过程中产生了两种新的生物型，表明它相对不稳定。我们的结果表明，CaMV的野生型群体包含一系列具有对比生物学特性和不同稳定性的感染性基因组变体。我们认为，在每个感染周期中，由于相对较小的基因组变化，可能会发生各种显著的病毒表型变化。
