Transcriptome Analysis Of The Auxin Key Genes In Populus Davidiana×P.alba Var.pyramidalis Response To Trichoderma Asperellum And Alternaria Alternata

In this study,after the leaves and roots of tissue culture seedlings of Populus davidiana×P.alba var.pyramidalis(Shanxin poplar)were induced for 48 h by Trichoderma asperellum or/and Alternaria alternata,12 cDNA libraries of stem tips,leaves and roots were constructed using RNA-Seq technology.The expression and regulation of the key genes involved in auxin biosynthesis and signal transduction of Shanxin poplar were analyzed at the transcriptome level under different treatments by T.asperellum or/and A.alternata.The main results are as follows:A total of 107.72 Gb Clean Data with Q30 no less than 93.07% were generated using illumina high-throughput sequencing technology.A total of 40151 genes based on alignment to P.trichocarpa genome were annotated into COG,KOG,GO,KEGG,NR and Swiss-Prot databases.The differential expression genes(DEGs)were detected with Fold Change?1 and FDR<0.05.There were the most DEGs in leaves of poplar seedlings infected by Alternaria.The DEGs in stem tip were more than other tissues when the seedlings were induced by Trichoderma.Besides,the number of DEGs in roots were the most when the seedlings were induced by Alternaria-Trichoderma.10 key DEGs were obtained in auxin synthesis pathway including YUCCA,ALDH and UGT74 B family genes.Expression patterns of DEGs showed that the up-regulation of ALDH3I1 gene via tryptamine pathway involved in auxin biosynthesis in stem tips and roots of the seedlings were mainly induced by Trichoderma-roots colonization.The differential expression of YUCCA genes(coding YUCCA protein in indole-3-pyruvic acid pathway which was the major pathway involved in auxin biosynthesis)in stem tips of the seedlings were mainly affected by Alternaria-leaves infection.What's more,the UGT74 B genes involved in auxin biosynthesis via indole-3-acetaldoxime pathway in leaves and roots of the seedlings were significantly up-regulated induced by Trichoderma-Alternaria.118 key DEGs were obtained in auxin signal transduction pathway including AUX1,ARF,AUX/IAA,SAUR,GH3,E1,E2,SCF complex(E3)family genes.Expression patterns of DEGs displayed that the differential expression of SAUR,AUX/IAA in stem tips of the seedlings were mainly induced by Trichoderma-roots colonization.And the differential expression of SAUR,AUX/IAA,GH3 in leaves was mainly affected by Alternaria-leaves infection.And the changes of expression patterns of SAUR,AUX/IAA,GH3 in roots were induced by Trichoderma-Alternaria.In addition,the expression of genes involved in ubiquitin mediated proteolysis had a little changes induced by the different treatments of Trichoderma or/and Alternaria.A total of 33 different ARF genes were found through the analysis of genes structure and function in cDNA libraries of Shanxin poplars,in which 22 DEGs were selected.Expression patterns of DEGs revealed that the differential expression of ARFs in the stem tips were mainly induced by Trichoderma-roots colonization.And the differential expression of ARF genes in the leaves were mostly affected by Alternaria-leaves infection.Meanwhile,the differential expression of ARFs in the roots was mostly affected by Trichoderma-Alternaria,and there were 8 ARF genes down-regulated expression.In addition,expression changes of most ARFs were little.The results of the RT-qPCR of 4 DEGs(ARF)indicated that their expression patterns were consistent with that of their transcriptome sequencing.