芥菜型油菜BjA09.TT8和BjB08.TT8基因调节类黄酮的合成

Regulation of flavonoid synthesis by BjA09.TT8 and BjB08.TT8 genes in Brassica juncea

bHLH类转录因子TT8具有调控植物类黄酮合成的功能。本研究采用同源克隆法,在芥菜型油菜紫叶芥中获得了2个TT8拷贝,分别命名为BjA09.TT8和BjB08.TT8,它们分别编码521和517个氨基酸。定量表达分析表明,这2个拷贝在叶中的表达量均显著高于茎和根中,且都响应茉莉酸(JA)信号,在50μmol L^(–1)的茉莉酸甲酯处理0.5 h后表达量均达到峰值;利用毛状根体系过表达发现,BjA09.TT8和BjB08.TT8分别可使紫叶芥和绿叶芥菜型油菜四川黄籽的毛状根中总黄酮含量升高,同时对类黄酮合成基因Bj.CHS的表达具有促进作用,说明二者在功能上具有冗余性。分别在野生型拟南芥和拟南芥tt8突变体中过表达BjA09.TT8和BjB08.TT8发现,过表达拟南芥植株叶片颜色变紫,植株总黄酮和原花色素含量显著升高。本研究表明,BjA09.TT8和BjB08.TT8基因能够促进芥菜型油菜类黄酮的合成,为进一步解析芸薹属植物原花色素合成的调控机制提供了参考。

bHLH transcription factors TT8 can effectively regulate the biosynthesis of plant flavonoids.In this study,two copies of TT8 were obtained in Brassica juncea by homologous cloning method,and named BjA09.TT8 and BjB08.TT8,which encoded 521 and 517 amino acids,respectively.Interestedly,qRT-PCR showed that the relative expression levels of the two copies in leaves were significantly higher than those in stems and roots,both responded to jasmonic acid(JA)signal,and the relative expression levels of Bju.TT8 reached maximum after 50μmol L^(-1) methyl jasmonate treatment for 0.5 hour.Furthermore,we found that both Bj.TT8 can increase the contents of total flavonoids in hairy roots of purple leaf mustard and green leaf mustard cultiver Sichuan Yellow Seed by hairy root system overexpression assay.It promoted the expression of flavonoid synthesis Bj.CHS,indicating they acted as redundant function.Over expression of BjA09.TT8 and BjB08.TT8 of wild-type Arabidopsis and Arabidopsis tt8 mutant revealed that the leaf colour of overexpressed Arabidopsis plant turned purple.Moreover,the contents of total flavonoid and proanthocyanidins increased significantly.In summary,BjA09.TT8 and BjB08.TT8 genes could promote the synthesis of flavonoids in Brassica juncea,which provided a reference for further analysis of the regulatory mechanism of proanthocyanidin synthesis in Brassica.