| Herbivorous spider mites are highly destructive arthropod pests that threaten agricultural production.According to the different host range,it can be divided into two categories:polyphagous spider mites(such as Tetranychus truncatus)and specifical spider mites(such as Tetranychus evansi).In theory,polyphagous feeding is more beneficial to spider mites adapting to a new environment than specifical,and specifical or Oligotrophic properties allow spider mites to better utilize the host’s nutrition and adapt to the host.At present,the molecular genetic mechanism of the evolution of spider mite diet is unclear.In order to reveal the mechanism,this study took the Tetranychus truncatus and the Tetranychus evansi as the material,and compared the changes in the fitness of the two during the transfer of host and the response mechanism of the gene transcription level.In this experiment,the spider mite(Ttr)was transferred from bean(B)to tomato(T)and eggplant(E),and the spider mite(Te)was transferred from tomato(T)to bean(B)and eggplant(E).The comparison of the fitness of the two spider mites in the F0 generation after transfer to a new host;the differences in the transient transcriptome expression of the two spider mites after 24 hours of transfer were analyzed.At the same time,we also sequenced and analyzed the mitochondrial genome of Tetranychus evansi,and analyzed the expression of genes related to energy metabolism on the mitochondrial genomes of Tetranychus truncatus and Tetranychus evansi,after their hosts were transferred.experiment result shows:1.Tetranychus truncatus transferred from the original host bean to eggplant and tomato,its egg production and hatching rate were significantly reduced,and Tetranychus evansi transferred from the original host tomato to bean,its egg production was significantly reduced,indicating that the two leaves To some extent,mites have host specialization.Tetranychus truncatus only lays eggs on tomatoes that are significantly lower than Tetranychus evansi indicating that Tetranychus evansi may be extremely specialized for tomatoes.The egg laying volume of Tetranychus truncatus transferred to eggplant is significantly higher than that of Tetranychus evansi to eggplant,indicating that Tetranychus evansi may not compete with Tetranychus truncatus on the new host eggplant The advantage of solitary diet in Solanaceae.The difference in egg production of Tetranychus evansi from tomato to eggplant is not significant,but the egg production of bean is significantly reduced,showing a trend of gradually decreasing the suitability from its original host to the near source host to the far source host.2.The results of transcriptome analysis showed that there were 9951 genes that were significantly differentially expressed between the transcriptome of Tetranychus urticae on tomato and 24 hours on bean,of which 6455 genes were up-regulated,There were 3496 genes that were down-regulated;there were 9584 genes that were significantly differentially expressed between the transcriptome of Tetranychus urticae feeding on tomato and 24 hours on eggplant,of which 4772 genes were up-regulated,down-regulated 4812 genes.There were 4159 genes with significant differential expression between the transcriptome of Tetranychus urticae eating 24 hours on beans and 24 hours on tomatoes,of which 1598 genes were up-regulated and 2561 genes were down-regulated;There were 12088 genes that were significantly differentially expressed between the transcriptome of Tetranychus urticae eating 24 hours on kidney beans and 24 hours on eggplants,including 6925 genes that were up-regulated and 4163 genes that were down-regulated.The GO and Pathway functional analysis of the significantly different genes showed that:1)Pathways and entries related to compound metabolism are in TeT-VS-TeE,TtrB-VS-TtrE,TeT-VS-TeB,and TtrB-VS-TtrT.All four comparison groups showed significant enrichment.We speculate that the spider mite metabolic activity in the body is significantly enhanced after transferring the host.2)Gene families related to detoxification and metabolism include:carboxyl/cholinesterase,cytochrome P450 monooxygenase,lysosome,and carbohydrate metabolism-related pathways and entries are all significant in the TtrB-VS-TtrT comparison group Sexual enrichment,but there is no pathway of enrichment related to detoxification metabolism or digestion and absorption in the TtrB-VS-TtrE comparison group,indicating that Tetranychus truncatus is extremely unsuitable after it is transferred to tomatoes.Genes related to detoxification and metabolism in the body respond actively.In the process of adapting to new hosts,detoxification metabolism and digestion and absorption related genes play a key role.The pathways related to protein absorption and lipid metabolism were significantly enriched in the two comparison groups TeT-VS-TeB and TeT-VS-TeE,and only the pathways related to ABC transporters were enriched in the TeT-VS-TeB comparison group,Indicating that the ABC transporter may play a key role in the adaptation process of Tetranychus evansi to distant hosts.In summary,we found that both the feeding-only Tetranychus evansi and the polyphagous Tetranychus truncatus regulate the adaptability of the spider mite to the host by regulating feeding and digestion behaviors.3.The whole mitochondrial genome of the Tetranychus evansi is a typical circular DNA with a length of 13064 bp.The A+T content of the mitochondrial genome J chain was 84.47%.We have identified a total of 37 genes,including 13 protein-coding genes,2 rRNA genes,and 22 tRNA genes.Through transcript reads,we compared the responses of genes related to energy metabolism on the mitochondrial genomes of two spider mites during the process of transferring hosts.It was found that the expression patterns of 13 protein-encoding mitochondrial genes in Tetranychus evansi and Tetranychus urticae were similar,indicating that the protein-encoded mitochondrial genes are species-specific and species-specific.The expression levels of COX3 and ND4 genes in Tetranychus truncatus are significantly higher than Tetranychus evansi,indicating that Tetranychus truncatus may have higher energy conversion efficiency and can better feed different host plants,so its host range is relatively wide. |
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