Cui Xiaofeng, Tao Xiaorong, Xie Yan, Fauquet Claude M, Zhou Xueping
Institute of Biotechnology, Zhejiang University, Hangzhou 310029, People's Republic of China.
J Virol. 2004 Dec;78(24):13966-74. doi: 10.1128/JVI.78.24.13966-13974.2004.
We report here that all 25 isolates of Tomato yellow leaf curl China virus (TYLCCNV) collected from tobacco, tomato, or Siegesbeckia orientalis plants in different regions of Yunnan Province, China, were associated with DNAbeta molecules. To investigate the biological role of DNAbeta, full-length infectious clones of viral DNA and DNAbeta of TYLCCNV isolate Y10 (TYLCCNV-Y10) were agroinoculated into Nicotiana benthamiana, Nicotiana glutinosa, Nicotiana. tabacum Samsun (NN or nn), tomato, and petunia plants. We found that TYLCCNV-Y10 alone could systemically infect these plants, but no symptoms were induced. TYLCCNV-Y10 DNAbeta was required, in addition to TYLCCNV-Y10, for induction of leaf curl disease in these hosts. Similar to TYLCCNV-Y10, DNAbeta of TYLCCNV isolate Y64 was also found to be required for induction of typical leaf curl diseases in the hosts tested. When the betaC1 gene of TYLCCNV-Y10 DNAbeta was mutated, the mutants failed to induce leaf curl symptoms in N. benthamiana when coinoculated with TYLCCNV-Y10. However, Southern blot hybridization analyses showed that the mutated DNAbeta molecules were replicated. When N. benthamiana and N. tabacum plants were transformed with a construct containing the betaC1 gene under the control of the Cauliflower mosaic virus 35S promoter, many transgenic plants developed leaf curl symptoms similar to those caused by a virus, the severity of which paralleled the level of betaC1 transcripts, while transgenic plants transformed with the betaC1 gene containing a stop codon after the start codon remained symptomless. Thus, expression of a betaC1 gene is adequate for induction of symptoms of viral infection in the absence of virus.
我们在此报告，从中国云南省不同地区的烟草、番茄或东方菝葜植物中收集的25株中国番茄黄化曲叶病毒（TYLCCNV）分离株均与DNAβ分子相关。为了研究DNAβ的生物学作用，将TYLCCNV分离株Y10（TYLCCNV - Y10）的病毒DNA和DNAβ的全长感染性克隆通过农杆菌介导接种到本氏烟草、黏毛烟草、烟草品种Samsun（NN或nn）、番茄和矮牵牛植株中。我们发现单独的TYLCCNV - Y10能够系统感染这些植物，但不诱导症状。除了TYLCCNV - Y10外，还需要TYLCCNV - Y10 DNAβ才能在这些宿主中诱导卷叶病。与TYLCCNV - Y10类似，TYLCCNV分离株Y64的DNAβ也被发现是在所测试的宿主中诱导典型卷叶病所必需的。当TYLCCNV - Y10 DNAβ的βC1基因发生突变时，与TYLCCNV - Y10共接种时，突变体在本氏烟草中不能诱导卷叶症状。然而，Southern杂交分析表明突变的DNAβ分子能够复制。当用含有受花椰菜花叶病毒35S启动子控制的βC1基因的构建体转化本氏烟草和烟草植株时，许多转基因植物出现了类似于病毒引起的卷叶症状，其严重程度与βC1转录本水平平行，而用在起始密码子后含有终止密码子的βC1基因转化的转基因植物仍无症状。因此，在没有病毒的情况下，βC1基因的表达足以诱导病毒感染症状。
