The Effects Of Different Resistant Wheat Cultivars On The Transcriptome Response And Wing Polyphenism Of Sitobion Avenae

The resistance of plant to insects mainly depends on the nutrient restriction and toxic metabolites,and the specific way can be inferred from the changes of nutrient metabolism and detoxification metabolism system of pests.The grain aphid,Sitobion avenae,is a major pest of wheat,which is mainly controlled by chemical pesticides.In order to facilitate the breeding of aphid-resistant wheat cultivars,this study speculates on the resistance mechanism of resistant wheat from the differences in the transcriptome of S.avenae reared on different resistant wheat cultivars.It was also investigated whether S.avenae can increase the wing rate of offspring to escape from the resistant wheat,and the regulation mechanism of wing polyphenism was studied.First,the differences in performance,nutrient ingestion,and transcriptome of S.avenae feeding on different resistant wheat cultivars were studied.The results showed that aphids had lower body weight and fecundity when feeding on wheat cultivar ‘Xiao Yan 22'(XY22)than on ‘Xi Nong 979'(XN979),although the phloem sap of XY22 had a higher nutritive quality(amino acid:sucrose ratio).Aphids feeding on XY22 also had a lower honeydew excretion rate than on XN979,suggesting that aphids ingested less phloem sap from XY22.Transcriptome data of S.avenae reared on XN979 and XY22 for 9 d showed that there were 600 differentially expressed genes(DEGs),and 11 of the top 20 KEGG pathways significantly enriched with DEGs were involved in nutrient metabolism.We found 81 DEGs associated with nutritional metabolism,22 of which were significantly upregulated in aphids feeding on XY22 and 59 of which were significantly downregulated in aphids feeding on XY22.Only 18 DEGs were related to detoxification metabolism,12 of which were upregulated in the aphids feeding on XY22.The above results indicate that the quantity and quality of phloem nutrition available to aphids are both important for the growth and development of aphids,and the higher resistance of XY22 is mainly due to the reduction of phloem sap ingested by aphids,rather than relying solely on toxic metabolites.Then,the effects of nutrition,female parent and Myzus persicae on the wing type of offspring were studied.The results showed that XY22 did not significantly increase the wing rate of S.avenae,but the wing rate was positively correlated with the density of nymphs;there was no significant difference in the wing rate when nymphs were reared on pre-infected and control wheat at 1 aphid / wheat and 30 aphids / wheat;the wing rate of nymphs when 1 S.avenae was crowded was significantly lower than that when 15 S.avenae were crowded;when 1 S.avenae was crowded with 14 M.persicae,the wing rate of nymphs was also increased,but the effect of crowding stimulus between S.avenae and M.persicae on nymphs was not as strong as that between S.avenae.To explore the mechanism of the impact of the crowding degree of nymphs on the wing polyphenism,we performed the transcriptome of 2nd instar nymphs(the female parent was in a high crowding)feeding on XN979 at 1 aphid/ wheat(Xn S)and 30 aphids / wheat(Xn M).There were 43 DEGs were related to cuticle protein,6 of which were downregulated in Xn S.One gene coding ecdysone 20-monooxygenase was downregulated in Xn S.From GO enrichment analysis,DEGs were significantly enriched in the membrane of cellular component,the lipid and sugar metabolism of biological process,and oxidoreductase and peptidase activity and structural constituent of cuticle of molecular function.In the top 20 KEGG pathways significantly enriched with DEGs,DEGs were significantly enriched into 5 sugar metabolism-related pathways,3 amino acid metabolism-related pathways,2 lipid metabolism-related pathways and 3 energy signal transduction related pathways.The above results indicate that the wing polyphenism of S.avenae is affected by the crowding degree of pre-natal adults and post-natal nymphs;the regulatory mechanism of wing polyphenism is multi-level,which may be related to lipid and sugar metabolism and energy distribution,and the insulin signaling pathway participate in the wing development of aphids.