We cloned a MYB transcription factor named CsMYB123 from the tea plant(Camellia sinensis) cultivar 'Zijuan' using RT-PCR.Bioinformatics analysis of CsMYB123 gene showed that it contains a 915 bp ORF that encodes a protein with 304 amino acid residues,an estimated molecular weight of 34.07 kD and an isoelectric point of 8.69.Based on an analysis that utilized BLAST online tools,we conclude that CsMYB123 belongs to the MYB gene family and is a R2R3-MYB protein.Our molecular evolutionary tree analysis of the CsMYB123 protein and all of the MYB transcription factors in A rabidopsis thaliana indi-cates that the CsMYB123 protein is most closely related to AtMYB123 and is a member of subgroup 5, which is one of the 22 R2R3-MYB subgroups.CsMYB123 is not predicted to have an N-terminal signal peptide or a transmembrane domain.CsMYB123 is predicated to be a hydrophilic protein that is localized to the nucleus.T he qPCR results indicated that the expression level of CsMY B123 gene in different tissues was as following:the first leaf and a bud > the second leaf > the third leaf > the fourth leaf > old stem> tender stem,with the expression of CsMYB123 gene in the first leaf and a bud was 15.68 fold higher than that in tender stem;However,expression of CsMYB123 was down-regulated under the treatment of IAA,ABA,ET H and GA3.We detected anthocyanin content in different tissues of ' Zijuan' tea plant, which was listed as below:the second leaf > the first leaf and a bud > the third leaf > the fourth leaf >tender stem > old stem,and the content in the second leaf and the first leaf and a bud were 15 times and 11 times higher than that in old stem,respectively.Based on the study above,we found that CsMYB123 gene was highly expressed in tender shoots of 'Zijuan' tea plant,and the expression level of CsMYB123 gene was positively correlated with the content of anthocyanin in different tissues.Thus,CsMYB123 may promote the accumulation of anthocyanins in tea plant.%该实验以茶树品种'紫娟'为试验材料,利用RT-PCR方法,从茶树cDNA中克隆得到一个R2R3-MYB型基因(CsMY B123).生物信息学分析显示,CsMY B123基因的开放阅读框为915 bp,编码304个氨基酸,蛋白分子量约34.07 kD,理论等电点为8.69,含有2个保守的M YB结构域,编码1个R2R3-M YB蛋白;CsM YB123蛋白与拟南芥(A rabidopsis thaliana)MYB转录因子家族第五亚组的AtMYB123亲缘关系最近;CsMYB123属于亲水性蛋白,无N端信号肽,可能定位于细胞核上.荧光定量PCR分析表明,CsMY B123基因在茶树各组织的表达量大小依次为:一芽一叶>第二叶>第三叶>第四叶>老茎>嫩茎,且在一芽一叶中的表达量是嫩茎的15.68倍;但CsMYB123的表达受IAA、ABA、ETH和GA3的抑制.花青素含量检测显示,茶树'紫娟'各组织中花青素的含量高低依次为:第二叶>一芽一叶>第三叶>第四叶>嫩茎>老茎,且第二叶和一芽一叶的含量分别为老茎的15倍和11倍.研究发现,CsMY B123基因在茶树'紫娟'的新稍中高水平表达,且其表达模式与不同组织中的花青素含量呈较好的正相关关系,推测 CsMY B123基因与茶树花青素合成的调控相关.
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