Studies On The Response Mechanisms Of Pine Caterpillar Enzymatic System To Pine Induced Resistance

Different amounts of pine caterpillars (Dendrolinus punctatus tabulaeformis Tsai etLiu) were feeded on the Chinese Pine (Pinus tabulaeformis) in pure forest and mixedforest and sampled at fifth and seventh instar. For exploring the resistance responses ofpine caterpillar to Chinese Pine that stimulated by feeding and forest types in naturalenvironment and revealing the counter-defense mechanism of pine caterpillars to thedifferent induced resistance of Chinese Pine, the changes of major detoxificationenzymes, protective enzymes and digestive enzymes activity as well as the expressionlevels of the relative genes of major detoxification enzymes in pine caterpillar wereanalysed. The research would provide a theoretical basis for the study of coevolution andbiological adaptation of the Chinese Pine and pine caterpillars and the ecologicalregulation of pine caterpillar population under environmental stress condition. Theresults are as follows:1.The changes of detoxification enzyme in pine caterpillarThe changes of detoxification enzyme activity in pine caterpillar under theinfluence of Chinese pine stimulated by different feeding degree were studied. Theresults showed that the CarE activity within7thinstar pine caterpillar gradually increasedwith the increase of the feeding stimulation degree to the Chinese pine in two foresttypes, the GSTs activity and P450content within pine caterpillar at5thand7thinstarsignificantly increased with the increase of the feeding stimulation degree in two foresttypes, Ace was not significantly difference among different treatments. Those resultsindicated that CarE, GSTs and P450were the anti-defense adaptability enzymes of pinecaterpillars against Chinese Pine resistance.The results of the study on the changes of detoxification enzyme activity in pinecaterpillar under the influence of different forest types showed that the GSTs activity andP450content in pine caterpillar under the influence of Chinese Pine in mixed forest werehigher than that in pure forest with the same degree of feeding stimulation, while theCarE and Ace activity in pine caterpillar were not significantly difference amongdifferent treatments. The results indicated that the Chinese Pine in different forest typeshad different resistance to pine caterpillars which was a reason to lead to the activity and content changes of the adaptive enzymes in pine caterpillar.2.The changes of protective enzyme in pine caterpillarThe changes of protective enzyme activity in pine caterpillar under the influence ofChinese pine stimulated by different feeding degree were studied. The results showedthat the SOD and CAT activity within pine caterpillar at5thand7thinstar significantlyincreased with the increase of the feeding stimulation degree to the Chinese pine in twoforest types, while the POD in pine caterpillar had no obviously linear variation in acertain range.Those results indicated that SOD、POD were the anti-defense adaptabilityenzymes of pine caterpillars against Chinese Pine resistance.The results of the study on the changes of protective enzyme activity in pinecaterpillar under the influence of different forest types showed that the SOD and CATactivity in pine caterpillar under the influence of Chinese Pine in mixed forest werehigher than that in pure forest with the same degree of feeding stimulation,while thePOD activity in pine caterpillar under the influence of pure forest were higher than thatin mixed forest with the same degree of feeding stimulation.The results indicated thatprotective enzyme activity changed in pine caterpillar under the influence of differentforest types.3.The changes of digestive enzymes in pine caterpillarThe changes of digestive enzyme activity in pine caterpillar under the influence ofChinese pine stimulated by different feeding degree were studied. The results showedthat the protein activity within pine caterpillar at5thand7thinstar significantly increasedwith the increase of the feeding stimulation degree to the Chinese pine in two foresttypes, the lipase and amylase activity within7thinstar pine caterpillar graduallyincreased with the increase of the feeding stimulation degree to the Chinese pine in twoforest types. Those results indicated that protein was the anti-defense adaptabilityenzyme of pine caterpillars against Chinese Pine resistance, the lipase and amylase werethe anti-defense adaptability enzymes of pine caterpillars against Chinese pine resistanceat the higher instar stage (main damaging stage).The results of the study on the changes of digestive enzyme activity in pinecaterpillar under the influence of different forest types showed that the protein,lipase andamylase activity in pine caterpillar under the influence of pure forest were higher thanthat in mixed forest with the same degree of feeding stimulation.The results indicatedthat the mixed forest produced more inhibition of digestive enzyme than pureforest,which was a reason to lead to the activity changes of the main digestive enzymesin pine caterpillar.4.The changes of relative expression levels of genes of main detoxification enzymesin pine caterpillar The changes of relative expression levels of genes of main detoxification enzymesin pine caterpillar under the influence of Chinese pine stimulated by different feedingdegree were studied. The results showed that the relative expression levels of GSTs genein pine caterpillar at5thand7thinstar had significantly difference with the CK in twoforest types and it increased with the increase of the feeding stimulation degree to theChinese pine. The relative expression levels of Ace gene was not significantly differencewith CK.Those results indicated that the higher gene expressed the higher activitychanged,and indicated GSTS was the anti-defense adaptability enzymes of pinecaterpillars against Chinese Pine resistance at the level of gene.The results of the study on the changes of relative expression levels of genes ofmajor detoxification enzymes in pine caterpillar under the influence of different foresttypes showed that the relative expression levels of GSTs gene under the influence ofChinese Pine in mixed forest were higher than that in pure forest with the same degree offeeding stimulation, the relative expression levels of Ace gene was not significantlydifference among different treatments.The results indicated that the Chinese Pine indifferent forest types had different resistance to pine caterpillars, which led to thechanges of the adaptive enzymes activity in pine caterpillar and the changes werecausesed by the induction of gene expression.