Transcriptome Characterization And Isolation And Expression Analysis Of R2R3-MYB Genes In Chinese Fir(Cunninghamia Lanceolata)

Chinesefir (Cunninghamialanceolata(Lamb.)Hook) is our country’s importantconiferous fast-growing tree species，and how to improve the nature of wood is one of themain breeding objectives. However, in the aspect of wood property breeding, domesticbreeders is to improve the wood density of Chinese fir, wood color trait as the goal tocarry out a number of conventional breeding. But research involving wood traits of themolecular mechanism of the formation was relatively less。In this tudy, the transcriptomesof nine tissues from Chinese fir were analyzed using the IlluminaHiSeq2000sequencing platform. Approximately40million paired-end reads were obtained,generating3.62gigabase pairs of sequencing data. These reads were assembled into83248Unigenes with an average length of449bp. Of these Unigenes,16750were assignedto Gene Ontology classes, and14877were clustered into ortholo gousgroups. Themajority of the genes encoding the enzymes in the biosynthetic pathways of cellulose andlignin were identified in the Unigene dataset by targeted searches of their annotations.Fifteen full-length cDNAs encoding MYB genes were isolated from Chinese firusing RACE of transcriptome data. They all have complete ORF and the amino acidsequences contain the functional domains of R2R3MYB. Amino acid residue of DBDidentity of ClMYB proteins compared with Picea glauca MYBs up to96%.The expression analysis showed that different ClMYBs had their mRNA products indifferent organs with varied levels. ClMYB1、ClMYB3�'�ClMYB6mRNA expressionlevels were highest in leaf, while ClMYB2、ClMYB13�'�ClMYB14were highest in root,ClMYB5�'�ClMYB12were highest in female cone and ClMYB15was highest in malecone. ClMYB11was both highest in root and female cone.In the expression of stem, theexpression of ClMYB1and ClMYB2in lignified stem were significantly higher thannon-lignified stem. By the further research of ClMYB1and ClMYB2, they were bothpredominantly expressed in xylem, and their expression levels of two-year-old stem werehigher than one-year-old stem. After the application of three hormones of IAA、GA3andBR by12hours, ClMYB1and ClMYB2were induced to different extent. During thecompression wood formation, the expression level of ClMYB1in the compression area ofxylem reached1.4times that of the opposite wood after10days bending. The ClMYB2expression was up-regulated in the compression wood. The Pearson correlation analysisof ClMYB1and ClMYB2between12lignin syntnesis related enzyme showed thatClMYB1had very significantly positive correlation with ClC4H、ClCOMT、ClPAL3andhad positive correlation with ClC3H、ClCCoAOMT2, but had significantly negativecorrelation with ClCCoAOMT2and negative correlation with ClPAL2. ClMYB2had verysignificantly positive correlation with ClCAD1and positive correlation withClCCoAOMT2, but significantly negative correlation with ClPAL2and negativecorrelation with Cl4CL. Those result show that ClMYB1、 ClMYB2may by regulate those genes involved in the lignin biosynthetic pathway.Transgenic tobacco with ClMYB1and ClMYB2lead to the flower delay, the plantsshorter, the leaves largen and the petiole more stiffness. Most transgenic tobacco withClMYB1flowering with no seed and the seed yield was extremely low and transgenictobacco with ClMYB2lowering with no seed. Transverse sections of transgenic tobaccowith ClMYB1、ClMYB2show that the content of lignin in transgenic tobacco was morethan in check test plant. The result show that ClMYB1and ClMYB2may involved in thelignin biosynthetic pathway.