Constitutive activation of brassinosteroid signaling in the Arabidopsis elongated-D/bak1 mutant
Constitutive activation of brassinosteroid signaling in the Arabidopsis elongated-D/bak1 mutant
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DOI：
10.1007/s11103-012-9963-5
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发表时间：
2012-11-01
影响因子：
5.1
通讯作者：
Choe, Sunghwa
中科院分区：
文献类型：
--
作者：
Chung, Yuhee;Choe, Vitnary;Choe, Sunghwa
油菜素类固醇（BR）生物合成或信号基因的缺陷导致矮化植物，而这些基因的过度表达增加整体身高。拟南芥elongated-D（elg-D）突变体与BR过表达株系具有表型相似性，表明其在BR途径中的意义。在这里，我们确定elg-D如何影响BR信号传导。由于elg-D拯救了BR受体突变体bri 1 -5植物的矮化，但在BR不敏感的bin 2/dwf 12 -1D植物中没有，因此elg-D似乎在BR信号传导中在bri 1 -5和bin 2/dwf 12 -1D之间起作用。我们发现，elg-D有一个表油菜素（epi-BL）的反应增加，BES 1转录因子被转移到elg-D的去磷酸化形式，BR响应基因，SAUR-AC 1的表达，在elg-D上调，BR生物合成基因，DWF 4和CPD的转录，反馈抑制下调。因此，内源性水平的CS和BL以及生物合成中间体的elg-D突变降低，而基础水平的BR信号被升高。基于图位的克隆和测序显示elg-D与BR共受体蛋白BAK 1是等位基因，并且在胞外富含亮氨酸重复（LRR）结构域的第三重复中具有Asp（122）到Asn的取代。与BAK 1/ELG参与病原体相关分子模式（PAMPs）的感知的发现一致，bak 1/elg-D植物表现出增加的假单胞菌生长。因此，bak 1/elg-D通过刺激BR信号来促进拟南芥的生长，但以牺牲其对生物应激因素的反应能力为代价。因此，BAK 1/ELG BR共受体在由其LRR结构域介导的BR信号传导中起重要作用。
Defects in brassinosteroid (BR) biosynthetic or signaling genes result in dwarfed plants, whereas overexpression of these genes increases overall stature. An Arabidopsis elongated-D (elg-D) mutant shares phenotypic similarities with BR overexpression lines, suggesting its implication in BR pathways. Here, we determine how elg-D affects BR signaling. Since elg-D rescued dwarfism in bri1-5 plants, a BR receptor mutant, but not in BR-insensitive bin2/dwf12-1D plants, elg-D appears to act between bri1-5 and bin2/dwf12-1D in BR signaling. We found that elg-D had an increased response to epibrassinolide (epi-BL); that the BES1 transcription factor was shifted toward the dephosphorylated form in elg-D; that the expression of a BR responsive gene, SAUR-AC1, was upregulated in elg-D; and that transcription of BR biosynthetic genes, DWF4 and CPD, was downregulated by feedback inhibition. Thus, endogenous levels of CS and BL as well as biosynthetic intermediates were reduced by the elg-D mutation, whereas basal levels of BR signaling were elevated. Map-based cloning and sequencing revealed that elg-D is allelic to the BR co-receptor protein, BAK1, and has an Asp(122) to Asn substitution in the third repeat of the extracellular leucine-rich repeat (LRR) domain. In agreement with the finding that BAK1/ELG is involved in the perception of pathogen-associated molecular patterns (PAMPs), the bak1/elg-D plants exhibited increased Pseudomonas syringae growth. Therefore, bak1/elg-D promotes Arabidopsis growth by stimulating BR signaling at the expense of its readiness to respond to biotic stress factors. The BAK1/ELG BR co-receptor thus plays an important role in BR signaling that is mediated by its LRR domain.