| Global climate change is the most important environmental problem,and the increasing concentration of greenhouse gases such as carbon dioxide(CO2)in the atmosphere is one of the main causes.According to the report of the intergovernmental panel on climate change(IPCC),the global CO2 concentration has been rising continuously since the industrial revolution,and it has reached around 412 ppm now.Moreover,it is estimated that the atmospheric CO2 concentration will reach twice of the current level at the end of this century.As the photosynthetic raw material of plants,elevated CO2 concentration in the atmosphere is not only beneficial to improve the plant photosynthesis rate and productivity,promote the growth and development of plants,and dilute plant leaf N concentration,improve leaf biomass,carbohydrate content and C/N ratio,lower the quality of the nutrition of plants,but also leading to the biological characteristics of insect herbivores,physical characteristics,feeding behavior and so on.Frankliniella occidentalis(Pergande)belongs to the Thripidae family of Thysanoptera,it is the typical rasping-sucking mouthparts insect,which is a worldwide invasive pest with devastating damage to vegetables,flowers,fruits and other crops.The thrips originated in North America and spread to Asia in the 1990s.In China,F.occidentalis was firstly found in Beijing in 2003,and now spread all over the country,including Yunnan,Zhejiang,Jiangsu,Shangdong,etc.Based on the background of climate change,elevated CO2 concentration is chosen as the environmental factors in this study.Closely tied to the production practice,we investigated the effects of elevated CO2 on the sucking mouthparts pests,F.occidentalis,and their interaction between host plants,Phaseolus vulgaris.It will be conducive to further define the disaster law and dynamic of the western flower thrips to the agricultural production under elevated atmospheric CO2 concentration.In this study,we tested the effects of elevated CO2 on nutrients,secondary metabolites of P.vulgaris,and the growth,reproduction and molecular mechanism of F.occidentalis.In addition,the effects of F.occidentalis feeding on P.vulgaris on the detoxification enzyme activity of thrips and the nutrients and antioxidant enzyme activity of host plants were studied;Furthermore,we measured the effects of F.occidentalis feeding on the immunoregulation mechanism of callose in P.vulgaris at elevated CO2.Main results for this study were as follows:1.Effect of elevated CO2 on Phaseolus vulgaris and Frankliniella occidentalisTo investigate how elevated CO2 affects the growth,development and reproduction of F.occidentalis by changing the nutrient and defensive compounds in P.vulgaris and in particularly,the hormonal regulation of the transcription factors in F.occidentalis,the amino acids,soluble sugar and soluble protein,as well as jasmonic acid(JA),salicylic acid(SA)and total saponins in P.vulgaris grown at ambient and elevated CO2 were examined.In addition,the larval duration,survival rate,weight,longevity and fecundity of F.occidentalis were also measured,as well as the transcript expression levels of JH,MH and Vg genes in thrips.Elevated CO2 increases the content of amino acids,soluble sugar(SS),soluble protein(SP)and jasmonic acid(JA)in P.vulgaris,but decreases the salicylic acid(SA)and total saponins(TS).Besides,elevated CO2 shortens the larval development and longevity of females of F.occidentalis,lowers their survival rate,and increases the weight and fecundity of thrips.The larval development of thrips positively correlated with the expression levels of br,Krh-1,EIP and JHEH.The longevity of thrips negatively correlated with JHEH,but positively correlated with ER and EIP.The weight and fecundity of thrips negatively correlated with Vg,but positively correlated with JHEH.We have demonstrated that elevated CO2 can enhance the nutrient quality of plants,therefore,accelerate the development and fecundity of thrips,which could be regulated by JH,MH and Vg.Our findings also show that elevated CO2 might affect the plants-thrips interaction by changing the defensive compounds of JA,SA and saponins.2.Effect of Frankliniella occidentalis feeding on the nutrient and antioxidant enzymes in Phaseolus vulgaris and the detoxifying enzymes in F.occidentalis at elevated CO2To investigate how elevated CO2 affects F.occidentalis fed with kidney bean P.vulgari and in particularly,the effect of elevated CO2 on the interaction between plant defense and thrips anti-defense,nutrients content and antioxidant enzymes activity in P.vulgari have been measured,as well as the detoxifying enzymes activity of adult thrips fed on the leaves with different thrips densities(10,20,40,80 thrips/leaf)and different feeding time(12,24,48,72 hours).The results showed that elevated CO2 increased soluble sugar,soluble protein,and free amino acids(FAA)content in non-thrips plants,and decreased superoxide dismutase(SOD)and peroxidase(POD)activity in these plants.Thrips feeding reduced the nutrients content in plants,and increased their SOD,catalase(CAT)and POD activity.Variation of nutrients content and antioxidant enzymes activity in plants showed an opposite tendency over thrips feeding time.After feeding,acetylcholinesterase(AchE),carboxylesterase(CarE),and microsomal mixed-function oxidases(MFO)activity in thrips increased to against plant defense response.More thrips densities induced stronger plant defense,in return,detoxifying enzymes in thrips increased over thrips number.Our study revealed that F.occidentalis could induce not only antioxidant-associated plant defense,but also the thrips detoxifying enzymes.We report that elevated CO2 might not only enhance plant defense to thrips attack,but also increase thrips anti-defense against plant defense.3.Effect of Frankliniella occidentalis feeding on callose synthase in Phaseolus vulgaris at elevated CO2In this study,we investigated the effect of elevated CO2 on the callose synthesis involved in the resistance of kidney bean,P.vulgaris,against the infestation and mechanical damage caused by F.occidentalis.Elevated CO2 elevated the silver damage,callose deposition,and the expression of CalS3 and CalS10 genes involved in a callose synthase(CalS)in thrips-infested bean leaves,while reducing PR2 gene expression related to the hydrolysis of callose.In addition,both infestation by thrips and mechanical damage increased the callose deposition in leaves and induced CalS and β-1,3-glucanases(BG)expression at both transcriptional and translational levels.Under ambient CO2,callose content in the mechanically-damaged plants(MDPs)and thrips-infested plants(TIPs)were positively correlated with CalS activity and the expression level of CalS3 and CalS10;BG activity was positively correlated with PR2 gene expression.Under elevated CO2,callose content in the MDPs and TIPs was negatively correlated with BG activity which also negatively correlated with the expression level of CalS10 and PR2.F.occidentalis feeding can induce callose synthesis and deposition in P.vulgaris leaves,especially under elevated CO2.Specifically,genes associated with CalS defense are upregulated while the expression of PR2 gene are downregulated.These results suggest that F.occidentalis feeding could induce the callose deposition in P.vulgaris,and elevated CO2 can modulate callose synthesis leading to a higher level of resistance in plants against thrips infestation.In conclusion,based on the climate change biology,plant physiology,ecology,insect physiology and biochemistry,and molecular biology,we used interdisciplinary research methods and systematically studied the effect of elevated CO2 on the nutrients and defensive compounds in P.vulgaris and the growth,development and fecundity of F.occidentalis,the effect of F.occidentalis feeding on the nutrient and antioxidant enzymes in P.vulgaris,as well as the detoxifying enzymes in F.occidentalis at elevated CO2,and the effect of F.occidentalis feeding on callose synthase in Phaseolus vulgaris at elevated CO2.It helps us to furtherly understand the interaction between P.vulgaris and F.occidentalis,and provides a theoretical basis for F.occidentalis damage in agricultural production under the climate change environment in the future,and it is conducive to the comprehensive management of F.occidentalis in the field. |
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