Analysis Of Drought Tolerance Mechanism Of Caragana Intermedia Based On Transcriptome

The climate in Northwest China is dry and cold,and Caragana plants have strong adaptability and stress tolerance.Caragana intermedia is a major tree species for improving the ecological environment in the western region.At present,the molecular mechanism of drought tolerance in Caragana intermedia remains unclear,and the understanding of key genes associated with drought tolerance is not comprehensive.In this study,RNA-Seq was made on the seedling samples of Caragana intermedia under different drought treatments.The main results are as following:1.Sequencing data analysis showed that the average Q20(%)of the control,6d and12 d drought treated samples were 98.33%,98.40% and 98.28% respectively;The average Q30(%)were 94.61%,94.79% and 94.54% respectively,indicating that the c DNA library obtained by this sequencing was of high quality.2.A total of 120342 unigenes were obtained from RNA-Seq data,of which 50659 unigenes can be annotated in the NR database.Common differentially expressed genes(DEGs)at different times of drought treatment and control were classified by GO function annotation.It was noted that the common DEGs could be enriched into 3 categories and114 subclasses,among which the proportion was high in the categories of metal ion binding,cation binding and oxidoreductase activity.KEGG annotation classification was appropriate to provide for the common DEGs as well.The results showed that the DEGs were mainly concentrated in metabolism,biosynthesis of other metabolites,transporters and other metabolic pathways,indicating that these processes may play a significant role in the growth and development of C.intermedia and tolerance to drought stress.3.In order to further consider the drought tolerance mechanism and key stress resistance related genes of C.intermedia,the metabolic pathway,transporter pathway and Phenylpropane biosynthesis pathway with a large number of DEGs under drought stress were analyzed.The results showed that 26 metabolism related genes were screened,and all of them were down-regulated;A total of 11 transporter related genes were screened,all of which were down-regulated genes;Nine genes related to Phenylpropane biosynthesis and metabolism were down-regulated;the analysis of common DEGs related to antioxidant enzyme encoding genes showed that down regulating the expression of antioxidant enzyme genes of POD family and P450 family was very important for C.intermedia to resist drought stress;In addition,some transcription factor encoding genes also showed a down-regulation trend.Part of the transcript level of DEGs had been verified by RT-q PCR,and the results were generally in consistent with the RNA-Seq data.These results indicated that drought inhibited the metabolism and Phenylpropane biosynthesis pathway,and had a great negative impact on the expression of transporters,transcription factor and antioxidant enzymes encoding genes of C.intermedia under drought stress.4.Totally 37511 SSRs and 699068 SNPs were screened from the transcriptome of C.intermedia under drought stress.This study analyzed the overall level gene expression and metabolic pathway changes of C.intermedia under drought stress through transcriptome sequencing,which provide a theoretical basis for the future study of the molecular mechanism of drought tolerance of C.intermedia.