【作者】 江彤；

【导师】 周雪平；

【作者基本信息】 浙江大学 ， 植物病理学， 2005， 博士

【摘要】 双生病毒在云南烟草、番茄和南瓜等多种作物上广泛发生,并已造成严重危害。由于双生病毒可能在杂草和农作物之间相互传染,为此我们对云南杂草上的的双生病毒开展了研究。 从云南赛葵、胜红蓟和稀硷上采集了39个双生病毒样品,部分序列测定表明,它们由不同病毒侵染。 Y160分离自赛葵,全序列测定表明,它与赛葵黄脉病毒(MYVV)的同源性最高,为82.2%。因此它是双生病毒新种,命名为云南赛葵黄脉病毒(Malvastrum yellow vein Yunnan virus,MYVYNV)。MYVYNV伴随有卫星DNA分子,它与MYVV DNAβ的序列同源性最高,为72.3%。序列比较发现MYVYNV可能是由MYVV和泰国番茄黄化曲叶病毒(TYLCTHV)重组形成的。构建了Y160 DNA-A和DNAβ的侵染性克隆。DNA-A单独接种以及DNA-A和DNAβ混合接种均可系统侵染本氏烟,DNAβ对于Y160 DNA-A的侵染不是必需的。DNAβ虽然不是症状的诱导因子,但伴随其辅助病毒DNA-A共同侵染时能加重病害症状,而且DNAβ可以显著增强DNA-A在植物中的积累。 从云南不同地区表现黄脉症状的赛葵上分离了20个DNAβ,序列比较发现,20个DNAβ分子均与MYVV DNAβ的序列同源性最高,达93.2-97.3%,说明这20个DNAβ均属于伴随MYVV的卫星DNA分子。20个DNAβ分子相互间的序列同源性高达93.0-99.8%,说明从云南不同地区赛葵上分离的20个MYVV DNAβ分子的序列变异相对较小。DNAβ的变异可能与病毒的寄主范围有关联,病毒的寄主范围越窄,伴随DNAβ的变异越小。 利用特异引物对采自云南各地的25个赛葵样品进行复合侵染检测。结果发现,25个样品中有13个能检测到MYVV和TYLCCNV的复合侵染,复合侵染率高达52%,说明田间自然发生的双生病毒复合侵染现象非常普遍。 测定了赛葵病毒样品Y193、Y194全基因组DNA-A。序列比较表明,Y193和Y194相互间的序列同源性高达98.7%,它们与TYLCCNV-To[Y25]的同源性最高,分别为88.0%和87.7%,进一步比较发现,Y193和Y194分离物可能是由TYLCCNV和另一病毒重组形成的。更多还原

【Abstract】 Geminiviruses have been reported infecting tobacco, tomato and squash commonly and have caused significant yield losses in Yunnan Province. Geminiviruses is likely to be transmitted between weeds and crops, so research works were carried out to identify viruses in weeds in Yunnan.Thirty-nine geminiviruses samples were collected from Malvastrum coromandelianum, Ageratum conyzoides and Siegesbeckia orientalis plants in Yunnan. Partial sequences showed these samples were infected by different geminiviruses.Y160 was isolated from M. coromandelianum, complete DNA-A sequence ofY160 has the highest sequence identity (82.2%) with that of Malvastrum yellow veinvirus (AJ457824), so it is a distinct begomovirus, for which the name Malvastrumyellow vein Yunnan virus (MYVYNV) is proposed. A satellite DNA molecule wasfound to be associated with MYVYNV, it shares the highest nucleotide sequenceidentity (72.3%) with MYVV DNA β. Comparison with other begomoviruses showsthat MYVYNV has probably arisen from recombination of MYVV and Tomatoyellow leaf curl Thailand virus. Infectious clones of DNA-A and DNA β of Y160were constructed. Y160 DNA-A alone or together with DNAβ could systemicallyinfect Nicotiana benthamiana plants, DNAβ molecule is not necessary for symptominduction of Y160 DNA-A but can increase symptom. Furthermore, DNAβ canincrease DNA-A accumulation in plants.Twenty DNAβ molecules were isolated from M. coromandelianum in different regions of Yunnan. Comparisons of the nucleotide sequences indicate that all the 20 DNAβ molecules have the highest nucleotide sequence identities (93.2-97.3%) with MYVV DNAβ , indicating all these molecules are associated with MYVV. The sequences of 20 DNAβ molecules share 93.0-99.8% overall nucleotide sequence identities with each other, indicating that variations are relatively less among the 20 DNAβ molecules originated from different regions in Yunnan. The variations of DNAβ probably have some relationship with virus host range. Narrow host range of virus results in less variations of DNAβ .Mixed infections were tested with specific primers among 25 M. coromandelianum samples collected in Yunnan. The results showed that the mixed infections of MYVV and Tomato yellow leaf curl China virus (TYLCCNV) were found in 13 samples. The ratio of mixed infection is more than 52%, indicating that mixed infections of begomoviruses occur commonly in fields.DNA-A sequences of Y193 and Y194 originated from M. coromandelianumsamples were determined. Comparisons of nucleotide sequences indicate that Y193 DNA-A shares relatively high sequence identity (98.7%) with that of Y194, and both Y193 and Y194 have the highest nucleotide sequence identities (88.0%, 87.7%) with that of TYLCCNV-To[Y25]. Further sequence analysis indicates that Y193 and Y194 probably have arisen from recombination between TYLCCNV and another virus.The complete DNA-A sequences of Y206, Y282 and Y283 from A. conyzoides showing yellow vein symptoms were determined. Comparisons with other begomoviruses show that Y206 DNA-A is most closely related to that of MYVV with 95.1% nucleotide sequences identity, and its associated DNAβ shares the highest nucleotide sequence identity (92.8%) with MYVV DNA β. Y282 and Y283 DNA-A have the highest sequence identities with that of TbCSV-[Y35] and TbLCYNV-[Y161] (99.7% and 97.3%), respectively, indicating that Y206, Y282 and Y283 are isolates of MYVV, TbCSV and TbLCYNV, respectively.Six DNA β molecules associated with TYLCCNV were isolated from S. orientalis showing vein swelling symptoms. They could be divided into two groups according to their sequence identities. DNAβ molecules in the same group were originated from the same region, and they shared more than 98.2% nucleotide sequence identities with each other, whereas DNAβ molecules between the two groups had relatively lower sequence identities (75.4-75.8%) with each other. The variations of TYLCCNV DNAβ molecules from S. orientalis in same region are less, whereas the variations of TYLCCNV DNAβ molecules in different regions are more.更多还原