| The susceptible strain (SS) and the spirotetramate-resistant strain (SR) cottonaphid (Aphis gossypii) were used in this study. The resistance mechanism tospirotetramate for A. gossypii was explored by biossays, transcriptomic survey andproteomic analysis methods.The resistant strain has been selected with spirotetramate through50generations.Adult aphids and3rd instar nymphs of the SR strain showed441.26-fold and11.97-fold resistance of spirotetramate to the susceptible strain, respectively. Compared withthe SS strain, the SR strain developed high level cross resistance to alpha-cypermethrin (237.80-fold) and bifenthrin (37.29-fold) but low level cross resistanceto acephate (4.65-fold), methidathion (4.82-fold), methomyl (4.32-fold), cyfluthrin(3.68-fold), esfenvalerate (2.96-fold), sulfoxaflor (3.33-fold) and imidacloprid (2.93-fold). Whereas, the SR strain showed no cross resistance to omethoate, chlorpyrifos,malathion, carbofuran, chlorfenapyr and thiamethoxam.Solexa sequencing technology was conducted to identify differentially expressedgenes (DEGs) between the susceptible and spirotetramat-resistant cotton aphid. Atotal of22,430,522and21,317,732clean reads were obtained from SR and SS cDNAlibraries respectively. These reads were assembled into35,222non-redundant (Nr)consensus sequences. A total of14,913,9,220,7,922,4,314and4,686sequences wereannotated using NR, Swiss-Prot, Gene Ontology (GO), Kyoto Encyclopedia of Genesand Genomes (KEGG) and Clusters of Orthologous Groups (COG) database. The SRstrain had1,287significantly changed unigenes compared with the SS strain, of which130genes were up-regulated and1,157genes were down-regulated (P≤0.001).Among these genes,440unigenes were annotated, consisting of114up-regulated and326down-regulated genes. The expression levels of heat shock protein70(Hsp70)and UDP-glucuronosyltransferase were significantly up-regulated in the SR strain.The genes that encoding cuticle proteins, energy ATP synthase, cytochrome coxidase， cuticle protein and salivary glue protein were dramatically decreased.Among the DEGs, cytochrome P4506A2was the only P450gene up-regulated in theSR strain. The expression levels of these DEGs which confirmed by real-time qPCRgot the same trends with the Solexa expression profiles. The effect of CYP6A2in the resistance to spirotetramate by RNAi was tested. The results showed that mortalityincreased significantly in the dsRNA-CYP6A2-fed aphids, the mortality increasedfrom33.32,45.57and61.38%in the control to54.41,67.56and70.05%in thedsRNA-CYP6A2-fed aphids under the25,50and100mg/L spirotetramat treatmentrespectively, which indicated that CYP6A2was related to the resistance onspirotetramate of A. gossypii. Repress the expression of CYP6A2also significantlyincrease the toxicity of alpha-cypermethrin to resistant aphids.The proteins were extracted from SR and SS strains of cotton aphid by usingTCA/acetone method, respectively. In total,493protein spots were detectable in thetwo-dimension polyacrylamide gel electrophoresis (2-DE). The intensities of35protein spots exhibited significant differences in abundance above2-fold between theSR strain and the SS strain. Of these spots,20protein spots were more abundant inthe SR strain and15protein spots were more abundant in the SS strain. Twenty sixdifferential expressed proteins were identified and categorized into several functionalgroups including carbohydrate and energy metabolism, antioxidant system, proteinfolding, amino acid metabolism, secondary metabolism and cytoskeleton protein, etc.Among these proteins, the acetyl-coA carboxylase (ACC), heat shock protein70,ubiquitin-conjugating enzyme, fatty acid synthase, UDP-glucose6-dehydrogenase, etc.are speculated to get related with the spirotetramat resistance in cotton aphids.It is a meaningful study on analyzing the resistance in spirotetramate pressureand exploring the appropriate mechanisms for co-evolution of the cotton aphid tospirotetramate. The research of cross-resistance provides theoretical guidance for theuse of different pesticides in the field. Above all，this study provides an importanttheoretical basis for the resistance mechanism to spirotetramate and valuableinformation for successful implementation of resistance management strategies for A.gossypii. |
PDF Full Text Request