MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana
MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana
复制标题
DOI：
10.1111/j.1365-313x.2008.03564.x
复制
发表时间：
2008-09-01
期刊：
影响因子：
7.2
通讯作者：
Lepiniec, Loic
中科院分区：
文献类型：
--
作者：
Dubos, Christian;Le Gourrierec, Jose;Lepiniec, Loic
在拟南芥中，几种MYB和碱性螺旋 - 环 - 螺旋（BHLH）蛋白与TTG1（WD重复序列）形成三元复合物，并调节参与花青素和原花青素（PA）生物合成的基因的转录。类似的MYB - BHLH - WDR（MBW）复合物控制表皮模式形成和细胞命运。一类小的MYB蛋白（R3 - MYB）已被证明在表皮细胞命运的调控中起重要作用，作为MBW复合物的抑制剂。然而，到目前为止，这些小的MYB蛋白中没有一种被证明可调节类黄酮生物合成。这里呈现的遗传和分子分析表明，编码一种与R3 - MYB相关蛋白的拟南芥MYBL2参与类黄酮生物合成的调控。两个独立的T - DNA插入突变体的幼苗中MYBL2活性的丧失导致花青素积累急剧增加。此外，MYBL2在种子中的过表达抑制了PA的生物合成。类黄酮含量的这些变化与几种花青素生物合成的结构基因和调控基因的mRNA水平升高密切相关。有趣的是，在拟南芥细胞中的瞬时表达分析表明，MYBL2在植物体内与MBW复合物相互作用，并直接调节类黄酮靶基因的表达。这些结果与在酵母中观察到的MYBL2与BHLH蛋白的分子相互作用完全一致。最后，MYBL2表达研究，包括其受光诱导胁迫的抑制，使我们能够对MYBL2的生理作用提出假设。综上所述，这些结果为类黄酮生物合成的转录调控带来了新的见解，并为进一步研究其发育和环境调控提供了新的线索和工具。
In Arabidopsis thaliana, several MYB and basic helix-loop-helix (BHLH) proteins form ternary complexes with TTG1 (WD-Repeats) and regulate the transcription of genes involved in anthocyanin and proanthocyanidin (PA) biosynthesis. Similar MYB-BHLH-WDR (MBW) complexes control epidermal patterning and cell fates. A family of small MYB proteins (R3-MYB) has been shown to play an important role in the regulation of epidermal cell fates, acting as inhibitors of the MBW complexes. However, so far none of these small MYB proteins have been demonstrated to regulate flavonoid biosynthesis. The genetic and molecular analyses presented here demonstrated that Arabidopsis MYBL2, which encodes a R3-MYB-related protein, is involved in the regulation of flavonoid biosynthesis. The loss of MYBL2 activity in the seedlings of two independent T-DNA insertion mutants led to a dramatic increase in the accumulation of anthocyanin. In addition, overexpression of MYBL2 in seeds inhibited the biosynthesis of PAs. These changes in flavonoid content correlate well with the increased level of mRNA of several structural and regulatory anthocyanin biosynthesis genes. Interestingly, transient expression analyses in A. thaliana cells suggested that MYBL2 interacts with MBW complexes in planta and directly modulates the expression of flavonoid target genes. These results are fully consistent with the molecular interaction of MYBL2 with BHLH proteins observed in yeast. Finally, MYBL2 expression studies, including its inhibition by light-induced stress, allowed us to hypothesise a physiological role for MYBL2. Taken together, these results bring new insights into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation of its developmental and environmental regulation.