Pan Li-Long, Chi Yao, Liu Chao, Fan Yun-Yun, Liu Shu-Sheng
Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
Virus Evol. 2020 Mar 4;6(1):veaa014. doi: 10.1093/ve/veaa014. eCollection 2020 Jan.
For many crop pathogens including viruses, high genetic variation provides them with potential to adapt to and prevail in a changing environment. Understanding genetic variation in viruses and their significance is a key to elaborate virus epidemiology and evolution. While genetic variation of plant viruses has been documented to impact virus-host interactions, how it affects virus-insect vector interactions remains elusive. Here, we report the impact of mutations in the coat protein of squash leaf curl China virus (SLCCNV), a begomovirus, on the interaction between the virus and its whitefly vectors. We characterized mutations in the coat protein of SLCCNV and found that some residues exhibited higher mutation frequency than the others. We assayed the impact of mutation on infectivity using agroinoculation and found these mutations marginally affect virus infectivity. We further analyze their functions using virus acquisition and transmission trials and found some of mutations resulted in altered transmission of SLCCNV by different species of the whitefly complex. We then identified the key amino acid residue(s) involved by constructing several mutant viruses and found that a single-residue mutation in the coat protein of SLCCNV was sufficient to significantly alter the whitefly transmission characteristics of SLCCNV. We examined the competition between different genotypes of SLCCNV in plant infection and whitefly transmission. We found that mutations in the coat protein did not alter the fitness of SLCCNV in plants, but they rendered the virus more competitive in transmission by certain species of whiteflies. Our findings indicate that mutations in the coat protein may play a key role in both the adaptation of begomoviruses to the changing vector populations and the evolution of begomoviruses.
对于包括病毒在内的许多作物病原体而言，高度的遗传变异使其有潜力适应不断变化的环境并在其中占优势。了解病毒的遗传变异及其意义是阐明病毒流行病学和进化的关键。虽然植物病毒的遗传变异已被证明会影响病毒与宿主的相互作用，但其如何影响病毒与昆虫载体的相互作用仍不清楚。在此，我们报告了双生病毒中国南瓜曲叶病毒（SLCCNV）外壳蛋白突变对该病毒与其粉虱载体之间相互作用的影响。我们对SLCCNV外壳蛋白中的突变进行了表征，发现一些残基的突变频率高于其他残基。我们通过农杆菌接种测定了突变对感染性的影响，发现这些突变对病毒感染性的影响很小。我们进一步通过病毒获取和传播试验分析了它们的功能，发现一些突变导致不同种类粉虱复合体对SLCCNV的传播发生改变。然后，我们通过构建几种突变病毒确定了相关的关键氨基酸残基，发现SLCCNV外壳蛋白中的单个残基突变足以显著改变SLCCNV在粉虱中的传播特性。我们研究了不同基因型的SLCCNV在植物感染和粉虱传播中的竞争情况。我们发现外壳蛋白中的突变并未改变SLCCNV在植物中的适合度，但使该病毒在某些种类粉虱的传播中更具竞争力。我们的研究结果表明，外壳蛋白中的突变可能在双生病毒适应不断变化的载体种群以及双生病毒的进化过程中都发挥着关键作用。
