The Assessment Of Invasiveness And Study On The Chemoreception Mechanism Of Cydia Pomonella,based On Its Genome Data

With increasing globalization,invasive alien species(IAS)dramatically threaten the agriculture,forestry,ecological environment and human health.Understanding the invasion mechanism is important to early warning,monitoring and effective control.The successfully invasison event is determined by the invasiveness of alien species,the sensitivity or invasibility of ecosystem of the introduced region,as well as the introduction process.When forcus on the IAS,it is widely acknowledged that the successful invasion of IAS is due to its own dominant characteristics,which is known as the "inherent superiority hypothesis".However,the common characteristics for invasive insects are unclear.The codling moth,Cydia pomonella,is an invasive insect pest worldwide.It seriously threatens the fruit production such as apple and pear.However,the molecular mechanisms under its global distribution are unclear.Our group has finished the sequencing and annotation of the whole genome of codling moth.In this current thesis,based on the genome data and other invasive species genomes which are available,we have assessed the invasiveness of insects and explored the chemoreception mechanism of colding moth,by using database platform construction methods,comparative genomic analysis methods,mechine learning and ecochemical methods.We firstly constructed the genome database of IAS “InvasionDB” to provide big data support for revealing the invasion mechanism of IAS.Secondly,based on the InvasionDB,the common genomic characteristics of invasive insects were analyzed,and a machine learning classifier was constructed to qualitatively determinate insect invasiveness,and the invasiveness index was proposed to quantitatively evaluate insect invasiveness.Subsquently,a comparative analysis of the chemoreception gene families which play important roles in the invasion of codling moth was performed,and the functions of a pair of key genes(CpomOR3a and CpomOR3b)which expanded were verified.The main results and conclusions are as follows:(1)Construction of genome database for invasive speciesIn order to provide an integrated analysis platform of genome data for the research of invasive mechanism,we collected all the genome data of IAS globally and constructed the genome database of IAS,named InvasionDB.InvaisonDB includes 103 invasive animals(56 invasive insects)and 34 invasive plants.We identified 38 important gene families and three non-coding RNAs(miRNA,rRNA and tRNA)for these IAS.The functionality for search,BLAST,JBrowse and downloads are provided by InvasionDB.(2)Estimation of insect invasiveness by machine learningWe conducted a comparative genomic analysis of 37 invasive insect species and seven non-invasive insect species,showing that the gene families associated with defense,protein and nucleic acid metabolism,reproduction,chemosensory function,and transcriptional regulation were significantly expanded in invasive insects.By using these expanded gene families,we proposed an invasiveness index and quantitatively estimated the invasiveness of other 100 insect species with genome data,classifying them as highly,moderately,or minimally invasive.Insects possessing all these five aforementioned expanded gene families are highly invasive,and vice versa.In addition,a logistic-regression classifier was trained to qualitatively predict insect invasiveness,achieving 94.4% accuracy.Both methods predicted that the codling moth was an invasive insect with a high invasion index of 0.96.(3)Identification and evolution of chemosensory genes of codling mothWe identified the chemosensory genes of codling moth includes 35 OBPs,91 ORs,58 GRs and 59 IRs based on the high quality genome data.The phylogenetic anlysis showed that the expansion of CpomGOBP2,CpomOR2,CpomOR3,CpomGR19,CpomGR34,CpomGR68,CpomGR87,CpomIR7,CpomIR25,CpomIR41,CpomIR60,CpomIR75 and CpomIR143 maybe contribute to its invasiveness.Additionally,these expanded genes are usually tandem duplicates in the same chromosome,suggested that they were generated due to adaptive evolution during the invasive process.(4)The duplicate and functional verification of CpomOR3 gene in codling mothThe CpomOR3 is the receptor gene of pear ester which is the main chemical component of host plant volatiles for codling moth.We found CpomOR3 tandem duplicated during its evolution.They were named as CpomOR3 a and CpomOR3 b,respectively.CpomOR3 b was only expressed in the adult antennas,while CpomOR3 a was expressed in both the adult antennas and larva heads,and the expression level of these two genes in the female antennas was higher than that of the male.The results of fluorescence in situ hybridization(FISH)showed that these two genes were independently expressed in different neurons at adjacent locations,and the expression pattern was consistent with the expression profile data.The results of electrophysiological experiments showed that both genes had strong responses to pear ester and codlemone.The results of RNAi interference showed that simultaneous interference of these two genes could affect both the female’s and male’s response to pear ester and codlemone,while single interference of one gene only affect male’s response to these two compounds.The results of Y-tube olfactometer indoor assays was consistent with RNAi,that is the simultaneous interference of two genes significantly affected the selection behavior of both male and female adults on pear ester and the selection behavior of male adults on codlemone,while the single interference of CpomOR3 b could significantly affected the selection behavior of male adults on codlemone.The results explained the strong attractive effect of pear ester on both adults and larva of codling moth,as well as the molecular mechanism of the synergistic effect of pear ester on codlmone.In this thesis,we constructed the InvasionDB to provide an integrated analysis platform of genomic data for scientists.Based on the InvasionDB,we screened out the common inherent advantages in the genomes of invasive insects and used these characteristics of expanded gene families to predict and evaluate insect invasiveness.Subsequently,we identified the chemosensory genes which may promote the invasion of codling moth and revealed the mechanism of adaptive evolution of the duplicate of CpomOR3 gene in the global invasion of codling moth.These results help to understand the mechanism of insect invasion at the genome level and provide theoretical support for early warning and effective control of IAS.