The role of MYB34, MYB51 and MYB122 in the regulation of camalexin biosynthesis in Arabidopsis thaliana.
The role of MYB34, MYB51 and MYB122 in the regulation of camalexin biosynthesis in Arabidopsis thaliana.
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DOI：
10.3389/fpls.2015.00654
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发表时间：
2015
影响因子：
5.6
通讯作者：
Gigolashvili T
中科院分区：
文献类型：
--
作者：
Frerigmann H;Glawischnig E;Gigolashvili T
植保素、Camalexin和吲哚硫代葡萄糖苷不仅具有共同的进化起源和紧密相连的生物合成途径，而且控制共同的酶步骤的调节蛋白也受到相同的R2R3-MYB转录因子的调控。吲哚植保素Camalexin是模式植物拟南芥中的重要防御代谢物。吲哚类植物抗毒素和硫代葡萄糖苷似乎有共同的进化起源，并且在生物合成水平上是相互关联的：作为茶碱蛋白生物合成的关键中间体，吲哚-3-乙醛肟(IAOx)也是吲哚类硫代葡萄糖苷生物合成所必需的，并受到转录因子MYB34、MYB51和MYB122的严格控制。在myb34/51和myb51/122双倍和三倍MYB突变体中，Camalexin的丰度显著降低，表明这些转录因子在Camalexin的生物合成中起重要作用。此外，生物和非生物Camalexin诱导剂显著提高了MYB51和MYB122的表达。用IAOx或吲哚-3-乙腈饲喂三重突变株myb34/51/122，在很大程度上恢复了Camalexin的生物合成。相反，色氨酸不能补充该突变体的低camalexin表型，这支持了三个myb因子在aOx上游的camalexin生物合成中的作用。在三个MYB突变体中，Camalexin生物合成基因CyP71B15/PAD3和CyP71A13的持续表达没有受到负面影响，并且在培养的拟南芥细胞的反式激活试验中，MYB不能激活pCYP71B15：：uidA的表达。综上所述，这项研究揭示了MYB因子调节作为Camalexin前体的IAOx产生的重要性。
The phytoalexin camalexin and indolic glucosinolates share not only a common evolutionary origin and a tightly interconnected biosynthetic pathway, but regulatory proteins controlling the shared enzymatic steps are also modulated by the same R2R3-MYB transcription factors. The indolic phytoalexin camalexin is a crucial defense metabolite in the model plant Arabidopsis. Indolic phytoalexins and glucosinolates appear to have a common evolutionary origin and are interconnected on the biosynthetic level: a key intermediate in the biosynthesis of camalexin, indole-3-acetaldoxime (IAOx), is also required for the biosynthesis of indolic glucosinolates and is under tight control by the transcription factors MYB34, MYB51, and MYB122. The abundance of camalexin was strongly reduced in myb34/51 and myb51/122 double and in triple myb mutant, suggesting that these transcription factors are important in camalexin biosynthesis. Furthermore, expression of MYB51 and MYB122 was significantly increased by biotic and abiotic camalexin-inducing agents. Feeding of the triple myb34/51/122 mutant with IAOx or indole-3-acetonitrile largely restored camalexin biosynthesis. Conversely, tryptophan could not complement the low camalexin phenotype of this mutant, which supports a role for the three MYB factors in camalexin biosynthesis upstream of IAOx. Consistently expression of the camalexin biosynthesis genes CYP71B15/PAD3 and CYP71A13 was not negatively affected in the triple myb mutant and the MYBs could not activate pCYP71B15::uidA expression in trans-activation assays with cultured Arabidopsis cells. In conclusion, this study reveals the importance of MYB factors regulating the generation of IAOx as precursor of camalexin.