| In nature,the whole life cycle of plants is often accompanied by the invasion of various insects.However,herbivorous insects not only differ in the ability of plant resistance defense,but also differ in the ability of tolerance to plant resistance defense.Therefore,the difference in resistance defense and self defense ability of different insect-induced plants may cause fatal injury to low-tolerance insects on the same host plant.Helicoverpa armigera(H.armigera)and Aphis gossypii(A.gossypii)are two important agricultural pests in cotton plants,and their ecological niches overlap.However,the interaction between insects with different niches on the same host plant is rarely reported.Therefore,based on the interaction between H.armigera and A.gossypii mediated by cotton,this study explored the relationship between the two insects and inferred the mechanism of niche differentiation of the two insects through the interaction,which also laid a theoretical foundation for the scientific development of new strategies and technologies for ecological pest control.1.Effect of A.gossypii damage cotton plant on H.armigera1.1 Oviposition preference of H.armigera and influence on larval growth and developmentA.gossypii damaged cotton plants(BT & Non-BT)that had a significant avoidance effect on the oviposition of H.armigera adults(P< 0.001),which number of eggs laid by H.armigera on normal plants was twice as much as that on A.gossypii damaged plant.However,A.gossypii damaged cotton plants(Non-BT: CCRI-49)that promoted the growth and development of H.armigera larvae,including weight gain and increased pupation rate(P < 0.001)and reduced mortality.However,H.armigera could not survive on Bt whether it was harmful or not.These results indicated that the A.gossypii affected the oviposition of H.armigera adults in the temporal niche,but promoted the growth and development of H.armigera larvae in the spatial niche.1.2 Transcriptomics and metabolomics analysis to reveal the internal mechanism affecting the growth and development of H.armigeraTranscriptomic and metabolomic analysis showed that 13 genes involved in salicylic acid(SA)biosynthesis were significantly up-regulated after A.gossypii damaged cotton plants(P<0.001),and SA content was significantly increased by quantitative analysis of SA hormones(P <0.001),15 genes involved in jasmonic acid(JA)biosynthesis were significantly down-regulated under the regulation of SA(P<0.001).In addition,through the analysis of plant resistance defense genes,3 genes(GH＿D01G1968,GH＿A01G1852,GH＿D06G0527)were significantly up-regulated and involved in the regulation of CHi B(Basic endochitinase B)under A.gossypii stress,and 2 genes(GH＿A12G0288,GH＿D12G0420)were significantly up-regulated and involved in the regulation of PR1(Pathogenesis-related protein 1),1 gene(GH＿A03G0302)was significantly up-regulated and involved in the regulation of HSP90(Heat shock protein 90 k Da beta)and 1 gene(GH＿D04G0133)was involved in the regulation of RRS1-R(Probable WRKY transcription factor 52).The metabolomics results showed that after A.gossypii damaged cotton,cotton amino acids(L-histidine),sugars(fructose,maltotetraose,melezitose),lipids(lecithin,stearidonic acid)and alcohol(mannitol)metabolites that were significantly up-regulated(P<0.001),and the content of IAA(Indole acetic acid)hormones regulating the biosynthesis of these substances was also significantly increased(P<0.05).Feeding test of pure metabolites confirmed that the increase of these metabolites promoted the growth and development of H.armigera(P<0.001).It can be inferred that A.gossypii damaged the enrichment of amino acids,sugars and lipids in cotton plants by inhibiting the JA based plant resistance defense,thereby promoted the growth and development of H.armigera larvae.1.3 ConclusionThe cotton aphid can repel the oviposition of adult H.armigera.However,the inhibition effect of A.gossypii on plant resistance defense and the enrichment of amino acids,sugars and lipids promoted the growth and development of larval H.armigera,which provided the basis for the growth and development of larval H.armigera.It can be concluded that A.gossypii affects the oviposition preference of adult H.armigera in the temporal niche,and promotes the acquisition of food resources by H.armigera in the spatial niche.2.Effect of H.armigera damaged on A.gossypii2.1 Effects on the growth and development of A.gossypiiIn order to explore the influence of H.armigera on A.gossypii population after colonization,the influence of H.armigera on A.gossypii population was analyzed.The results showed that H.armigera damaged to cotton plants had significant inhibitory effect on A.gossypii population(P<0.001).The results of EPG analysis showed that H.armigera had significant inhibition on feeding efficiency of A.gossypii(P<0.001),indicating that H.armigera may affect the reproduction of A.gossypii by affecting its nutrient acquisition.In addition,H.armigera had a significant repellent effect on cotton plants feeding on A.gossypii(P<0.001).Through metabolite screening,Methyl anthranilate(MA)has significant repellent effect on A.gossypii feeding(P<0.001).In addition,jasmonic acid treatment significantly reduced the population of A.gossypii(P<0.001),suggesting that H.armigera may affect A.gossypii with low tolerance by stimulating JA based plant resistance defense.2.2 Transcriptomic and metabolomic analysisTranscriptome and metabonomics analysis revealed that the expression levels of genes involved in JA biosynthesis were significantly up-regulated after H.armigera damaged cotton plant(P<0.001),and JA as a regulated metabolite also significantly increased(P<0.001).In addition,the contents of terpenes,alkaloids and tannins,as downstream products regulated by JA,also significantly increased(P<0.001).Pure validation of these metabolites showed that Acetic acid Gossypol and Tannins had significant inhibitory effects on A.gossypii population(P<0.001),while methyl anthranilate(MA)had significant repellent effect on A.gossypii(P<0.001).The results showed that H.armigera inhibited the growth and development of A.gossypii and caused the escape of A.gossypii by regulating the changes of plant secondary metabolites.2.3 summaryH.armigera significantly increased the contents of terpenes,alkaloids and tannins,which inhibited the population of A.gossypii.The H.armigera induced the production of MA,a volatile metabolite,which had repellent effect on the feeding of A.gossypii,leading to the escape of A.gossypii.Therefore,it can be inferred that the plant resistance induced by H.armigera causes the A.gossypii to be inadaptable,which leads to the decrease of the population and the selection of the more adaptable space for feeding,resulting in spatial differentiation.3 ConclusionThis paper takes the ecological relationship between cotton,A.gossypii and H.armigera as the research object,and uses biological,ecological and omics techniques to reveal the cotton-mediated interaction relation between A.gossypii and H.armigera from different levels.The ecological and molecular mechanisms by which A.gossypii damaged cotton plants could promote the growth and development of H.armigera,and the ecological and molecular mechanisms by which the A.gossypii populations gradually escaped to extinction due to the plant resistance defense activated by H.armigera damage were revealed.The interaction between A.gossypii and H.armigera inferred from the results of this study not only provides a reference for exploring the evolutionary differentiation of A.gossypii and H.armigera,but also lays a theoretical basis for formulating new pest ecological control strategies and the development and application of plant-derived metabolites. |
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