Li Mingzhuo, Li Yanzhi, Guo Lili, Gong Niandi, Pang Yongzheng, Jiang Wenbo, Liu Yajun, Jiang Xiaolan, Zhao Lei, Wang Yunsheng, Xie De-Yu, Gao Liping, Xia Tao
State Key Laboratory of Tea Plant Biochemistry and Utilization, Anhui Agricultural UniversityHefei, China.
School of Life Science, Anhui Agricultural UniversityHefei, China.
Front Plant Sci. 2017 Jun 12;8:943. doi: 10.3389/fpls.2017.00943. eCollection 2017.
Green tea () abundantly produces a diverse array of phenylpropanoid compounds benefiting human health. To date, the regulation of the phenylpropanoid biosynthesis in tea remains to be investigated. Here, we report a cDNA isolated from leaf tissues, which encodes a R2R3-MYB transcription factor. Amino acid sequence alignment and phylogenetic analysis indicate that it is a member of the MYB4-subgroup and named as CsMYB4a. Transcriptional and metabolic analyses show that the expression profile of is negatively correlated to the accumulation of six flavan-3-ols and other phenolic acids. GFP fusion analysis shows CsMYB4a's localization in the nucleus. Promoters of five tea phenylpropanoid pathway genes are isolated and characterized to contain four types of AC-elements, which are targets of MYB4 members. Interaction of CsMYB4a and five promoters shows that CsMYB4a decreases all five promoters' activity. To further characterize its function, is overexpressed in tobacco plants. The resulting transgenic plants show dwarf, shrinking and yellowish leaf, and early senescence phenotypes. A further genome-wide transcriptomic analysis reveals that the expression levels of 20 tobacco genes involved in the shikimate and the phenylpropanoid pathways are significantly downregulated in transgenic tobacco plants. UPLC-MS and HPLC based metabolic profiling reveals significant reduction of total lignin content, rutin, chlorogenic acid, and phenylalanine in transgenic tobacco plants. Promoter sequence analysis of the 20 tobacco genes characterizes four types of AC-elements. Further CsMYB4a-AC element and CsMYB4a-promoter interaction analyses indicate that the negative regulation of CsMYB4a on the shikimate and phenylpropanoid pathways in tobacco is via reducing promoter activity. Taken together, all data indicate that CsMYB4a negatively regulates the phenylpropanoid and shikimate pathways. A tea () is characterized to encode a R2R3-MYB transcription factor. It is shown to repressively control the phenylpropanoid and shikimate pathway.
绿茶大量产生多种有益于人体健康的苯丙烷类化合物。迄今为止，茶叶中苯丙烷类生物合成的调控仍有待研究。在此，我们报道了从叶片组织中分离出的一个cDNA，它编码一个R2R3-MYB转录因子。氨基酸序列比对和系统发育分析表明，它是MYB4亚组的成员，命名为CsMYB4a。转录和代谢分析表明，其表达谱与六种黄烷-3-醇和其他酚酸的积累呈负相关。绿色荧光蛋白融合分析表明CsMYB4a定位于细胞核。分离并鉴定了五个茶叶苯丙烷类途径基因的启动子，发现它们含有四种类型的AC元件，这些元件是MYB4成员的作用靶点。CsMYB4a与五个启动子的相互作用表明，CsMYB4a降低了所有五个启动子的活性。为了进一步表征其功能，在烟草植株中过表达该基因。所得转基因植株表现出矮小、叶片萎缩发黄和早衰的表型。进一步的全基因组转录组分析表明，参与莽草酸和苯丙烷类途径的20个烟草基因的表达水平在转基因烟草植株中显著下调。基于超高效液相色谱-质谱联用（UPLC-MS）和高效液相色谱（HPLC）的代谢谱分析表明，转基因烟草植株中总木质素含量、芦丁、绿原酸和苯丙氨酸显著降低。对这20个烟草基因的启动子序列分析鉴定出四种类型的AC元件。进一步的CsMYB4a-AC元件和CsMYB4a-启动子相互作用分析表明，CsMYB4a对烟草中莽草酸和苯丙烷类途径的负调控是通过降低启动子活性实现的。综上所述，所有数据表明CsMYB4a对苯丙烷类和莽草酸途径起负调控作用。一种茶树被鉴定为编码一个R2R3-MYB转录因子。它被证明对苯丙烷类和莽草酸途径起抑制作用。
