| The green peach aphid(Myzus persicae)is an extreme example of a genuine generalist,which can colonize more than 1000 different plants in more than 50 families.This remarkable ability makes M.persicae a highly destructive pest of many important crop species,causing huge economic losses in agriculture and forestry.Due to the ability of M.persicae to transfer between different hosts,single control technology cannot fundamentally solve the problem of aphid in agricultural systems.Elucidate the host adaptation mechanism is of great importance for the development of integrated control strategies.M.persicae can rapidly regulate gene expression to enhance host adaptability after host switching,we called transcriptional plasticity.Study on the role of transcriptional plasticity in host adaptation of the M.persicae could provide insights for the host adaptation mechanism of the polyphagous pests,which is expected to find a new direction in host adaptation research and provide a theoretical basis for integrated control strategies.In this study,we studied host adaptation differences of M.persicae in Brassica napus and Nicotiana benthamiana,and explored the influencing factors of its transcriptional plasticity.The main results are as follows:1.The adaptability of M.persicae on B.napus was significantly higher than that of N.benthamiana: By testing the fecundity and survival rate of the stable lines on rape and tobacco,the results show that,the fecundity and survival rate on B.napus was significantly higher than N.benthamiana.Use the stable lines perform hosts switch experiments,the fecundity will significantly decreased after host transfer from B.napus to N.benthamiana,and significantly increased when transferred from N.benthamiana to B.napus.The instar had a certain effect on the fecundity of M.persicae after host switching,especially transfer from N.benthamiana to B.napus.the third instar aphid showed a lower increase than the first instar aphid after host transfer.After host exchange,the survival rate of was significantly decreased when transferred from B.napus to N.benthamiana,while significantly increased when transferred from N.benthamiana to B.napus.2.M.persicae differentially expressed detoxification enzyme genes in B.napus and N.benthamiana.Transcriptome analysis of the stable M.persicae lines on B.napus and N.benthamiana.revealed that 536 genes were differentially expressed,249 genes were up-regulated and 287 genes were down-regulated in the B.napus stable line.It contains detoxification metabolism genes,glutathione S-transferase,UDP-glucuronosyl transferase,ATP-binding cassette transporter which related to pesticide resistance,cytochrome P450 s and Cathepsin B which related to secondary substance metabolism.Six genes related to detoxification of parasites were screened out from differential express genes to do q PCR detection,the results show that the expression levels of the six genes were significantly up-regulated in B.napus,which was consistent with the transcriptome results.3.M.persicae have more nutritious on B.napus.Using LC-MS to analyse the metabolites of M.persicae on B.napus and N.benthamian,218 differential metabolites were found,190 increased and 28 decreased on the B.napus stable line.The metabolites of M.persicae fed on B.napus contain more aspartic acid,glutamic acid and a variety of amino acid derivatives,and the trehalose was also enrich in B.napus.The metabolites of M.persicae fed on B.napus contain more flavonoids.M.persicae on B.napus have more abundant nutritious,whereas M.persicae on N.benthamian were subjected to strong stress.4.Host-driven rapid regulation of gene expression of M.persicae.We use the third-instar aphid do host-transfer experiment to detect the detoxification gene changes.Cathepsin B3 expression was up-regulated by over 30 times when M.persicae was transferred from N.benthamiana to B.napus,but down-regulated by 10 times when transferred from B.napus to N.benthamiana.The insect detoxification genes including CYP6CY3,UGT-2C,Car Es and GST was down-regulated after transfer to N.benthamiana,and up-regulated after transfer to B.napus.5.The effect of specialization on transcriptional plasticity of M.persicae.The thiamethoxam resistant and sensitive aphid host-specific and host-tolerant aphid were selected to do host transfer experiments.Cathepsin B3 was used as reporter gene to detect the difference of transcriptional plasticity.When transfer from N.benthamiana to B.napus,Cathepsin B3 up-regulated 13 times in aphid which acclimatize to M.persicae for a week,and more than 40 times in aphid which acclimatize to M.persicae for a week.After transfer from B.napus to N.benthamiana,Cathepsin B3 was down-regulated nearly 68 times in thiamethoxam sensitive type,and sensitive type was down-regulated about 4.6 times. |
