Investigation Of Ant Diversity In Northern Shaanxi And The Genetic Mechanism Of Ants Adapting To Desert Environment

Ants are an important part of terrestrial ecosystems and are often used as indicators for important biodiversity research.There are many species that can be used for biological control.Northern Shaanxi refers to Yan'an and Yulin regions,and its landforms include the Qiaoshan Mountains,Huanglong Mountains,Ziwuling Mountains and Longshan Mountains in the south,the Loess Plateau in the central part and the Mu Us Desert in the north.After more than 20 years of efforts to convert farmland to forests and prevent and control desertification,the ecological environment in northern Shaanxi has been significantly improved.In this paper,the species diversity of the ants in this area was systematically investigated to provide basic data for the study of biodiversity in northern Shaanxi.A comparative transcriptome study of ants in Mu Us desert,farmland and treated desert was conducted to explore the genetic mechanism of ant adaptation to desert environment.In the long evolutionary process,insects constantly improve their physiological and genetic mechanisms to adapt to adverse environments.In this study,the Illumina sequencing platform was used to sequence transcriptome Tetramorium caespitum from three environments in the Mu Us Desert.Firstly,by comparing the differentially expressed genes and metabolic pathways of T.caespitum distributed in Mu Us Desert,farmland and treated desert,the genes and molecular mechanisms related to drought adaptation were screened out.We further discovered two types of functional genes(cytochrome P450 gene and heat shock gene)related to its' drought-enduring habits.These results not only explained the gene of drought-enduring,but also provided mechanism of drought-enduring.The number and sequence of these genes were further excavated,and the overall expression patterns of these two genes were analyzed in three different environmental ants.The research results and main conclusions are as follows.1.In total 6160 ant specimens belonging to 29 species,14 genera and 3 subfamilies(Dolichoderinae,Formicinae and Myrmicinae)were recorded.There are 3 species in 3 genera of Dolichoderinae,20 species in 7 genera of Formicinae,and 6 species in 4 genera of Myrmicinae.Six species were reported for the first time from northern Shaanxi:Formica clara Forel,1886;Messor aralocaspius(Ruzsky,1902);Plagiolepis pygmaea(Latreille,1798);Technomyrmex elatior Forel,1902;Tetramorium chefketi Forel,1911 and Temnothorax ruginosus Zhou et al.2010.A new species,Proformica muusensis sp.nov.,was described and illustrated,easily distinguishable from Proformica buddhaensis for its gaster distinctly small.Pronotum has fewer sub-erect hairs and mesonotum longer than wider,much narrower than the pronotum.The CO I based phylogenetic tree of Proformica was constructed and support that Proformica muusensis sp.nov.is the sister species of P.mongolica and P.buddhaensis.2.The ant H index in northern Shaanxi was 1.0543-2.2085,the H index in Yuyang District was the lowest(1.0543),and H index in Shenmu County was the highest(2.2085).The E index was 0.6551-0.9033,the E index in Yuyang District was the lowest(0.6551),and the E index in Huanglong County was the highest(0.9033).The C index was 0.1444-0.4503,with the lowest in Shenmu County(0.1444)and the highest in Yuyang District(0.4503).3.Transcriptome sequencing of 12 samples from Mu Us Desert showed that 74.57Gb of Clean Data were obtained.The Clean Data of each sample was at least 5.74Gb,and the lowest Q30 value was 92.32%.A total of 100010 Unigene pieces were obtained after assembly,and the N50 of Unigene was 1548 bp.After blast with NR,Swiss-Prot and other gene and protein databases,48565 Unigene were annotated.Genetic structure analysis based on Unigene library was performed.4.The GO and KEGG annotation results showed that the genes involved in ribosome synthesis,protein synthesis in the endoplasmic reticulum and lipid anabolism were significantly up-regulated in the three environments.The genes involved in PI,Sphingolipid metabolism,Phenylalanine metabolism,Drug metabolism-cytochrome P450,and Metabolism of xenobiotics by cytochrome P450 were significantly up-regulated in the desert of T.caespitum,confirming that the arid environment promotes metabolic and immune responses,and this integration ensures energy balance and helps ants grow normally.Glutathione metabolism Protein and processing in endoplasmic reticulum were upregulated,suggesting that the ants were able to adapt to drought,possibly due to the regulation of heat stress response by heat shock Protein.5.By comparing the gene expression levels of cytochrome P450 and heat shock protein of ants in different environment groups,it was found that the expression levels of the same gene in the same environment were similar in the groups.The gene expression levels were different in different environments,some genes were significantly higher and some genes were lower,indicating different emphasis on gene function.6.The genes of cytochrome P450 related to drought-enduring are mainly Cyp303a1,CYP6K1 and Cyp4g1 genes,and the enrichment pathways are Secondary metabolites biosynthesis,transport and catabolism.Under drought conditions,ants expend more energy to increase the activity of detoxification enzymes,which leads to the enrichment of secondary metabolites in biosynthesis,transport and catabolism pathways under water stress.The genes of Heat shock protein related to droughtenduring are mainly heat shock cognate protein 70 and 1(2)efl genes,and the enrichment pathways are Posttranslational modification,protein turnover,chaperones pathway.It is repair of heat denatured proteins that is a key pathway in droughtenduring.