| Global warming has been an international concern for many years,and would be an endless issue to be discussed.Numerous researches revealed that CO2 concentration in atmosphere has reached its highest level in recent years,and will continue to rise.The increase of CO2 concentration was reported to impact the environmental degradation significantly.Hence in this study,we evaluated the effect of elevated CO2 concentration that could affect the plant(Populus davidiana × P.bolleana)and its pest(Lymantria dispar).Three different CO2 concentrations were used,which were 397 ppm as the current atmospheric CO2 concentration,and 550 ppm and 750 ppm as the prediction of elevated CO2 in the future.The CO2 concentration(397 ppm,550 ppm,750 ppm)was directly applied to Populus davidiana × P.bolleana,host plant of Lymantria dispar,for one month,and growth rate of plant was measured.Afterward,the 3rd instar of L.dispar was placed for feeding assay,and the growth rate and activities of detoxification enzymes of L.dispar were measured.Furthermore,qRT-PCR techniques were used to reveal the gene expression of L.dispar.The transcriptome and metabolomics of Populus davidiana × P.bolleana were also compared and analyzed.The main results are as follows:1.The RNA-seq study of Populus davidiana × P.bolleana was analyzed in response to elevated CO2.The total of clean read showed that 50498 Unigenes were obtained,which were annotated functionally.Based on comparison result,the differential expression according to KEGG was conducted.There were 60 DEGs in the three groups of samples,which 18 DEGs were up-regulated,and 5 DEGs were down-regulated.The highest number of differential expression genes was found in the Populus davidiana × P.bolleana on HCO2-vs-LCO2 group sample(2949),while the MCO2-vs-LCO2 group sample and HCO2-vs-MCO2 group sample were 1835 and 1632,respectively.The amount of down-regulated DEGs in HCO2-vs-LCO2 and MCO2-vs-LCO2 group sample was largely more than the up-regulated genes.As revealed by the functional annotation of DEGs,1493,772,and 790 number of DEGs in HCO2-vs-CO2,HCO2-vs-MCO2,and MCO2-vs-LCO2 group sample were involved in metabolic pathways,while 10.78%,10.62%and 10.38%of the total number annotated to the ribosome metabolism pathway(map03010),and 3.82%,4.66%and 2.66%annotated to the phenylpropane metabolic pathway(map00940),respectively.2.Non-target metabolomic was used to analyse the change of metabolites in Populus davidiana× P.bolleana treated with three different CO2 concentrations.XCMS software was used to extract the metabolite.The results showed that the total of 11603 positive ions and 10666 negative ions.In the positive ion mode,95 different metabolites were found in the three groups of CO2 concentration treatment group,while 69 were in negative ion mode.The results of the combined analysis of transcription group and metabolic group showed that ribosome metabolism pathway(map03010)and phenylpropane pathway(map00940)had the function of regulating metabolism of Populus davidiana × P.bolleana as response to the change of CO2 concentration.26 DEGs were up-regulated in ribosomal pathway,and the highest expression was 50S ribosomal protein L34(rpL34),while 35 DEGs were up-regulated in phenylpropane pathway,and the highest expression was caffeic acid-o-methyltransferase(OMT1).3.In order to determine the effects of different concentrations of CO2 on the growth rate and detoxification enzyme activity of Lymantria dispar.One-year-old Populus davidiana × P.bolleana seedlings were grown in CO2-enhanced environments for one month at three different concentration:397 ppm,550 ppm and 750 ppm.leaves of Populus davidiana × P.bolleana were fed to 3rd instar larvae of Lymantria dispar.It was found that the seedlings of Populus davidiana× P.bolleana treated with CO2 had significant effects on the growth of Lymantria dispar larvae,and at 96 h the growth rate of the larvae increased significantly.Carboxylesterase(CarE),cytochrome P450(P450),and glutathione S-transferase(GST)are important components of detoxification enzyme metabolism in insects.Lymantria dispar fed on Populus davidiana × P.bolleana under 750 ppm CO2 induced the up-regulation of P450 and GST activities at all time points,while CarE activity reached the highest in 550 ppm treatment group.4.q-RT PCR analysis was performed to explore the effects of different CO2 concentrations on detoxification enzyme genes of Lymantria dispar,the expression of 7 CYP genes(CYP6AB37,CYP6B53,CYP6AN15v1,CYP4L23,CYP4L24,CYP9A54v1,and CYP332A6)and 10 GST genes(GSTe3,GSTo1,GSTo2,GSTs1,GSTS2,GSTt1,GSTz1,GSTz2,GSTe1,and GSTe2).The results showed that at 96 h,except for CYP4L23,CYP9A54v1,and CYP6B53,CYP gene was significantly up-regulated,while GST gene was significantly down-regulated with the increase of CO2 concentration,indicating that CYP and GST family genes were involved in the detoxification process of gypsy moth. |
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