OsTGAP1, a bZIP Transcription Factor, Coordinately Regulates the Inductive Production of Diterpenoid Phytoalexins in Rice
OsTGAP1, a bZIP Transcription Factor, Coordinately Regulates the Inductive Production of Diterpenoid Phytoalexins in Rice
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DOI：
10.1074/jbc.m109.036871
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发表时间：
2009-09-25
影响因子：
4.8
通讯作者：
Yamane, Hisakazu
中科院分区：
文献类型：
--
作者：
Okada, Atsushi;Okada, Kazunori;Yamane, Hisakazu
水稻在病原入侵被识别为植物防御相关化合物后，会产生主要的二萜类植物抗菌素、莫内酯和植物cassanes。我们最近发现，莫内酯的生物合成基因聚集在水稻4号染色体上，并在诱导后共同表达，模仿病原体的攻击。由于植物中大多数代谢途径的基因不是以基因簇的形式组织的，因此有必要研究调节这些基因簇表达的机制。在这里，我们报道了一个几丁质寡糖激发子诱导的碱性亮氨酸拉链转录因子OsTGAP1，它是莫内酯生物合成所必需的，并调节簇中五个基因的表达。OsTGAP1的敲除突变体在激发子处理后几乎不表达5个聚集基因（OsCPS4、OsKSL4、CYP99A2、CYP99A3和OsMAS），也不产生单内酯。OsKSL7诱导植物cassane生物合成的表达在ostgap1突变体中也受到很大影响，尽管植物cassane积累仍然发生。相反，ostgap1过表达的细胞系在激发子的作用下表现出聚集基因的表达增强和单内酯的过度积累。此外，还观察到OsKSL7的表达增强和植物cassanes的过度积累。我们还发现，OsTGAP1过表达可以影响甲基赤藓糖醇磷酸途径中OsDXS3的转录上调，最终诱导二萜类植物抗毒素的产生。这些结果表明，OsTGAP1是水稻诱导二萜类植物抗毒素产生相关基因协调转录的关键调控因子，并主要对聚类基因的表达发挥重要作用。
Production of major diterpenoid phytoalexins, momilactones and phytocassanes, is induced in rice upon recognition of pathogenic invasion as plant defense-related compounds. We recently showed that biosynthetic genes for momilactones are clustered on rice chromosome 4 and co-expressed after elicitation, mimicking pathogen attack. Because genes for most metabolic pathways in plants are not organized in gene clusters, examination of the mechanism(s) regulating the expression of such clustered genes is needed. Here, we report a chitin oligosaccharide elicitor-inducible basic leucine zipper transcription factor, OsTGAP1, which is essential for momilactone biosynthesis and regulates the expression of the five genes in the cluster. The knock-out mutant for OsTGAP1 had almost no expression of the five clustered genes (OsCPS4, OsKSL4, CYP99A2, CYP99A3, and OsMAS) or production of momilactones upon elicitor treatment. Inductive expression of OsKSL7 for phytocassane biosynthesis was also largely affected in the ostgap1 mutant, although phytocassane accumulation still occurred. Conversely, OsTGAP1-overexpressing lines exhibited enhanced expression of the clustered genes and hyperaccumulation of momilactones in response to the elicitor. Furthermore, enhanced expression of OsKSL7 and hyperaccumulation of phytocassanes was also observed. We also found that OsTGAP1 overexpression can influence transcriptional up-regulation of OsDXS3 in the methylerythritol phosphate pathway, eventually leading to inductive production of diterpenoid phytoalexins. These results indicate that OsTGAP1 functions as a key regulator of the coordinated transcription of genes involved in inductive diterpenoid phytoalexin production in rice and mainly exerts an essential role on expression of the clustered genes for momilactone biosynthesis.