小麦TaMYB1A负调控苯丙烷代谢途径及植株的株高

Wheat TaMYB1A Negatively Regulates the Phenylpropanoid Pathway and Plant Height

苯丙烷途径是植物次生代谢产物合成的重要途径之一,可合成木质素、类黄酮和芥子酰基苹果酸类等化合物。该途径所产生的化合物不仅影响植物的生长发育及胁迫反应,还能用于生产香料、农药、染料、医药、饲料和生物质能源等。植物中的R2R3-MYB蛋白在植物次生代谢调节、器官发育和应对环境胁迫反应等方面均发挥重要的生物学功能。小麦(Triticum aestivum L.)是重要的粮食作物,在生产粮食的同时会产生大量秸秆等生物质;因此,研究小麦R2R3-MYB类转录因子在植物苯丙烷途径中的功能及调控机制对有效利用小麦秸秆具有重要意义。RT-PCR分析表明,TaMYB1A在小麦孕穗期的茎中表达水平较高;GFP-TaMYB1A融合蛋白在烟草表皮细胞中主要定位于细胞核;TaMYB1A在酵母系统中具有转录抑制活性。本研究以过表达TaMYB1A的转基因拟南芥株系为材料,分析了TaMYB1A对木质素积累/合成以及类黄酮化合物合成的影响。结果表明,过表达TaMYB1A抑制转基因拟南芥株系的株高(P<0.05),并显著降低了转基因拟南芥株系中木质素(P<0.05)和类黄酮(P<0.05)的合成。酵母单杂交结果显示,TaMYB1A能结合于拟南芥At4CL1、AtC4H、AtC3H和AtCHS以及小麦Ta4CL1和TaC4H1的启动子区;双荧光素酶报告系统显示,TaMYB1A抑制拟南芥中上述4个基因的表达;遗传学分析表明,TaMYB1A抑制小麦Ta4CL1和TaC4H1的表达;基因芯片和qRT-PCR结果表明,过量表达TaMYB1A抑制了转基因拟南芥苯丙烷途径中多数基因的表达;且转基因株系中4CL酶活性显著下降(P<0.05)。综上所述,小麦TaMYB1A属于R2R3型第四亚组MYB转录因子,通过与拟南芥和小麦苯丙烷途径关键基因的启动子结合并抑制相关基因的表达,从而负调控苯丙烷代谢途径及转基因株系的株高。

The phenylpropanoid pathway is one of the important pathways for synthesizing plant secondary metabolites,which can produce lignin,flavonoid,and sinapoylmalate.These compounds can not only affect the plant growth,development,and stress response,but also be used to produce perfume,pesticide,dye,medicine,feed,and biomass energy.R2R3-MYBs play important roles in regulating plant secondary metabolism,organ development,and in responding to environmental stresses.Wheat(Triticum aestivum L.)is an important food crop,but lots of straw will be produced accompanied by grain yields.Therefore,elucidating the function and regulatory mechanism of R2R3 MYBs of wheat is crucial for the effective utilization of the wheat straw.RT-PCR results showed that TaMYB1A was highly expressed in the wheat stems,and the GFP-TaMYB1A fusion protein was mainly localized in the nucleus of the N.benthamiana epidermal cells.TaMYB1A has transcriptional repressive activity in yeast cells.In this study,TaMYB1A-overexpressed transgenic Arabidopsis lines were generated to elucidate the effect of over-expression of TaMYB1A on the biosynthesis of lignin and flavonoid.Our results suggested that overexpres-sion of TaMYB1A inhibited the plant height(P<0.05)and decreased the lignin(P<0.05)and fla-vonoid(P<0.05)biosynthesis of the transgenic Arabidopsis plants significantly.TaMYB1A could bind to the promoters of the Arabidopsis At4CL1,AtC4H,AtC3H,and AtCHS as well as the wheat Ta4CL1 and TaC4H1 revealed by yeast one-hybrid(Y1H)assasy,the transcriptional repressive effect of TaMYB1A on At4CL1,AtC4H,AtC3H,and AtCHS was confirmed by dual-luciferase reporter systems and also on Ta4CL1 and TaC4H1 by a genetic approach.Gene chip and quantitative RT-PCR(qRT-PCR)results showed that overexpression of TaMYB1A down-regulated the expression of most of the key genes involved in the phenylpropanoid metabolism and decreased the 4CL activity(P<0.05)of the transgenic Arabi-dopsis plants significantly.As suggested above,the wheat TaMYB1A belongs to the subgroup 4 R2R3 MYB transcription factors.TaMYB1A could bind to the promoters of the key genes involved in phenylpro-panoid metabolism,repress their expression and negatively regulate the phenylpropanoid metabolism path-way and plant height.