| Tetranychus cinnabarinus is a polyphagous mite.It causes a serious damage to a variety of economic crops.T.cinnabarinus can feed on the chloroplast and cell sap of fence tissue cells in host leaf through piercing and sucking mouthparts,causing systemic damage to the host plant and inducing the plant defense response.When plant is attacked by pest,plant induces resistance by activating their internal defense system.Jasmonic acid is an endogenous growth regulator ubiquitous in higher plants,and its main role is to induce a defense response in wounds.Since exogenous jasmonic acid was reported to be beneficial for inducing resistance of plant,its physiological and biochemical mechanism has been one of the important research issues.In recent years,researchers have been trying to apply this theory to practical application,but in T.cinnabarinus,the relevant research is relatively lacking.Therefore,this study uses T.cinnabarinus-jasmonic acid-eggplant as the research system to analyze changes of eggplant jasmonic acid defense and its molecular mechanism,and the effect of T.cinnabarinus on jasmonic acid-induced eggplant.It provides a theoretical basis for clarifying the interaction mode between host plants and T.cinnabarinus mediated by jasmonic acid and exploring the control methods of environment-friendly T.cinnabarinus.The main findings of the thesis are as follows:1.High performance liquid chromatography was used to detect the changes in jasmonic acid content of eggplant in 1 day,4 days,and 7 days after being fed by T.cinnabarinus.The results showed that feeding by T.cinnabarinus caused an increase in the content of jasmonic acid in eggplant.The content of jasmonic acid changed the most after 1 day,reaching 14 times;The jasmonic acid content of eggplant decreased significantly after removing the feeding T.cinnabarinus for 3 days.It showed that the change of eggplant jasmonic acid content is directly related to the harm of T.cinnabarinus,and it proved that the feeding of T.cinnabarinus can cause the jasmonic acid defense reaction of eggplant.2.In order to explore the response mechanism of jasmonic acid signal caused by T.cinnabarinus feeding,the eggplant leaves before and after feeding by T.cinnabarinus were analyzed by transcriptome sequencing.The results showed that there were 5467 differentially expressed genes in 1 day after being fed by T.cinnabarinus,including 2980 of up-regulated genes and 2487 of down-regulated genes;4 days after being fed by T.cinnabarinus,there were 5902 differentially expressed genes in eggplant leaves,including 3332 of up-regulated genes and 2570 of down-regulated genes;After 7 days of feeding by the mites,there were 7830 differential genes in eggplant leaves,of which 4414 of genes were up-regulated and3417 of genes were down-regulated.It can indicate that the number of differentially expressed genes on eggplant leaves might increase with the increase of the feeding time of T.cinnabarinus.When the eggplant was fed by T.cinnabarinus for 1 day,the T.cinnabarinus were removed and the eggplant recovered for 3 days.There were 5557 of differentially expressed genes in eggplant leaves,of which 3268 of genes were up-regulated and2289 of genes were down-regulated.However,when the eggplant was fed by T.cinnabarinus after 4 days,the T.cinnabarinus were removed and the eggplant recovered for 3 days.There were 2996 of differentially expressed genes in eggplant leaves,of which 1942 of genes were up-regulated and 1054 of genes were down-regulated.The results showed that the number of differentially expressed genes in eggplant leaves would decrease after T.cinnabarinus were removed.It shows that eggplant can deal with the harm of T.cinnabarinus by changing the expression of some genes.3.According to the function analysis of the differentially expressed genes in eggplant leaves,11 genes in the jasmonic acid synthesis pathway were excavated,namely LOX6,LOX1.4,LOX2.1,LOX1.5,LOX3.1,AOS3,AOS1,AOC,OPR3,OPR2,OPR1.These genes were all up-regulated in various treatments,and they were basically consistent with the change trend of jasmonic acid content.The results suggest that the main reason for the increase of jasmonic acid content in eggplant leaves after feeding by T.cinnabarinus is the increased expression of genes in its synthesis pathway.Further analysis of the KEGG(Kyoto Encyclopedia of Genes and Genomes)found that the Phenylpropanoid biosynthesis pathway,which was enriched in the metabolite of coumarin,had the largest number of up-regulated genes in all treatments.Fluorescence spectrophotometer detection found that after T.cinnabarinus feeding and exogenous jasmonic acid treatment,the coumarin content in the eggplant leaves increased significantly.The above results prove that the feeding of T.cinnabarinus can cause the jasmonic acid content of eggplant leaves to increase,which in turn induces the increase of coumarin content.4.When T.cinnabarinus fed on eggplant leaves with exogenous jasmonic acid,its damage ability,the number of eggs,and population growth rate decreased significantly,and after feeding on eggplant leaves with exogenous coumarin,T.cinnabarinus showed a similar phenomenon to jasmonic acid treatment.The results of this study further proved that eggplant leaves had a jasmonic acid-coumarin-mediated defense response to resist the damage of T.cinnabarinus.5.Transcriptome analysis was used to analyze the response mechanism of T.cinnabarinus to jasmonic acid,and predict its adaptive mechanism to jasmonic acid defense response of eggplant.The sequencing results obtained a total of 164 differentially expressed genes.Gene function annotation revealed that genes encoding metabolic enzymes were up-regulated.The quantitative verification results showed that the carboxylesterase gene CCE12 was up-regulated by 10.3 times and the glutathione transferase gene GSTd02 was up-regulated by 3.5 times,which was the result of T.cinnabarinus in response to exogenous jasmonic acid treatment of eggplant.It shows that T.cinnabarinus can metabolize the secondary metabolites produced by plant defense by increasing the content of detoxification metabolic enzymes.Through the above results,this study explored the molecular mechanism of jasmonic acid defense in eggplant damaged by T.cinnabarinus,clarified the effect of jasmonic acid defense in eggplant on T.cinnabarinus,as well as explored the adaptive mechanism of T.cinnabarinus on jasmonic acid defense in eggplant. |
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