Overexpression of the bZIP transcription factor OsbZIP79 suppresses the production of diterpenoid phytoalexin in rice cells
Overexpression of the bZIP transcription factor OsbZIP79 suppresses the production of diterpenoid phytoalexin in rice cells
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DOI：
10.1016/j.jplph.2014.09.001
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发表时间：
2015-01-15
影响因子：
4.3
通讯作者：
Okada, Kazunori
中科院分区：
文献类型：
--
作者：
Miyamoto, Koji;Nishizawa, Yoko;Okada, Kazunori
植物抗菌素是植物在应对病原体攻击时产生的抗菌特化代谢物。莫内酯和植物cassanes是水稻中主要的二萜类植物抗毒素，它们是由源自甲基赤四醇磷酸（MEP）途径的香叶基香叶基二磷酸合成的。我们之前报道过，水稻细胞过度表达碱性亮氨酸拉链（bZIP）转录因子OsTGAP1，在响应几丁质寡糖激发子后，表现出单内酯和植物cassane的过度积累，同时高诱导表达单内酯和植物cassane的生物合成基因和MEP途径基因。为了更好地了解ostgap1介导的二萜类植物抗毒素产生的调控，我们使用酵母双杂交筛选鉴定了ostgap1相互作用的蛋白。在OsTGAP1相互作用的候选蛋白中，研究了TGA因子OsbZIP79，以验证其与OsTGAP1的物理相互作用以及参与植物抗毒素产生的调节。体外拉下实验表明，OsTGAP1和OsbZIP79表现出异二聚体和同二聚体的相互作用。双分子荧光互补分析也显示了OsTGAP1和OsbZIP79在体内的相互作用。有趣的是，在瞬时报告细胞实验中观察到OsbZIP79的反式激活活性，而OsbZIP79的过表达导致激发诱导的二萜类植物抗菌素生物合成基因的表达受到抑制，从而导致水稻细胞中植物抗菌素的积累减少。这些结果表明，OsbZIP79作为水稻细胞中由甲壳素寡糖激发子触发的植物抗毒素产生的负调节因子，尽管在OsbZIP79可以与OsTGAP1一起工作的条件下，它仍然是开放的。(C) 2014 Elsevier GmbH版权所有。
Phytoalexins are antimicrobial specialised metabolites that are produced by plants in response to pathogen attack. Momilactones and phytocassanes are major diterpenoid phytoalexins in rice that are synthesised from geranylgeranyl diphosphate that is derived from the methylerythritol phosphate (MEP) pathway. We have previously reported that rice cells overexpressing the basic leucine zipper (bZIP) transcription factor OsTGAP1 exhibit a hyperaccumulation of momilactones and phytocassanes, with hyperinductive expression of momilactone and phytocassane biosynthetic genes and MEP pathway genes, upon response to a chitin oligosaccharide elicitor. For a better understanding of OsTGAP1-mediated regulation of diterpenoid phytoalexin production, we identified OsTGAP1-interacting proteins using yeast two-hybrid screening. Among the OsTGAP1-interacting protein candidates, a TGA factor OsbZIP79 was investigated to verify its physical interaction with OsTGAP1 and involvement in the regulation of phytoalexin production. An in vitro pull-down assay demonstrated that OsTGAP1 and OsbZIP79 exhibited a heterodimeric as well as a homodimeric interaction. A bimolecular fluorescence complementation analysis also showed the interaction between OsTGAP1 and OsbZIP79 in vivo. Intriguingly, whereas OsbZIP79 transactivation activity was observed in a transient reporter assay, the overexpression of OsbZIP79 resulted in suppression of the elicitor-inducible expression of diterpenoid phytoalexin biosynthetic genes, and thus caused a decrease in the accumulation of phytoalexin in rice cells. These results suggest that OsbZIP79 functions as a negative regulator of phytoalexin production triggered by a chitin oligosaccharide elicitor in rice cells, although it remains open under which conditions OsbZIP79 can work with OsTGAP1. (C) 2014 Elsevier GmbH. All rights reserved.