宿主适应有可能引起昆虫共生微生物的快速遗传变异。共生病毒中的突变如何有利于宿主中的病毒适应性,甚至影响宿主对新环境的适应性仍然难以捉摸。这里,我们探索了共生病毒一个位点的遗传差异的作用,Acyrthosiphonpisum病毒(APV),寄主蚜虫对不利植物的适应。根据豌豆蚜虫蚕豆殖民地和蚕豆殖民地的转录组,在两个蚜虫菌落的APV基因组中发现了46个单核苷酸多态性(SNP)位点。一个SNP位于5,990,G5990A,位于RNA依赖性RNA聚合酶(RdRp)域,当寄主蚜虫从V.faba转移到低适应性植物V.villosa或紫花苜蓿时,显示出从G到A的优势。该SNP导致在RdRp中的位点196处从丝氨酸(S)取代为天冬酰胺(N)。尽管S196N被预测位于远离保守功能基序的随机线圈上,与S196型相比,N196型RdRp的聚合酶活性增加了44.5%.RdRp酶活性的提高与APV复制水平的提高有关,这对蚜虫是有益的,因为APV抑制了植物对蚜虫的抗性反应。研究结果表明,在共生病毒中选择的突变可能会在宿主适应新的环境条件时对宿主有利。
Host adaptation has the potential to cause rapid genetic variation in symbiotic microorganisms in insects. How mutations in symbiotic viruses favor viral fitness in hosts and even influence host adaptability to new environments remains elusive. Here, we explored the role of genetic divergence at one site of a symbiotic virus, Acyrthosiphon pisum virus (APV), in the host aphid\'s adaptation to unfavorable plants. Based on the transcriptomes of the pea aphid Vicia faba colony and Vicia villosa colony, 46 single nucleotide polymorphism (SNP) sites were found in the APV genomes from the two aphid colonies. One SNP at site 5,990, G5990A, located at the RNA-dependent RNA polymerase (RdRp) domain, demonstrated a predominance from G to A when the host aphids were shifted from V. faba to the low-fitness plants V. villosa or Medicago sativa. This SNP resulted in a substitution from serine (S) to asparagine (N) at site 196 in RdRp. Although S196N was predicted to be located at a random coil far away from conserved functional motifs, the polymerase activity of the N196 type of RdRp was increased by 44.5% compared to that of the S196 type. The promoted enzymatic activity of RdRp was associated with a higher replication level of APV, which was beneficial for aphids as APV suppressed plant\'s resistance reactions toward aphids. The findings showed a novel case in which mutations selected in a symbiotic virus may confer a favor on the host as the host adapts to new environmental conditions.