A Triantagonistic Basic Helix-Loop-Helix System Regulates Cell Elongation in Arabidopsis
A Triantagonistic Basic Helix-Loop-Helix System Regulates Cell Elongation in Arabidopsis
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DOI：
10.1105/tpc.112.105023
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发表时间：
2012-11-01
期刊：
影响因子：
11.6
通讯作者：
Ohme-Takagi, Masaru
中科院分区：
文献类型：
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作者：
Ikeda, Miho;Fujiwara, Sumire;Ohme-Takagi, Masaru
在植物中，碱性螺旋-环-螺旋（bHLH）转录因子在控制细胞伸长中起着重要作用。两个bHLH蛋白，PACLOBTRAZOL RESISTANCE1 （PRE1）和拟南芥ILI1结合bHLH1 (IBH1)，在响应油菜素内酯和赤霉素信号时拮抗调节细胞伸长，但这些因子调节细胞伸长的详细分子机制尚不清楚。在这里，我们确定了bHLH的细胞伸长转录激活因子（ace），并证明PRE1、IBH1和ace构成了一个三拮抗bHLH系统，竞争性地调节细胞伸长。在该系统中，ACE bHLH转录因子通过与其启动子区相互作用，直接激活细胞延伸酶基因的表达。IBH1通过与ace相互作用，从而干扰它们的DNA结合，负向调节细胞伸长。PRE1与IBH1相互作用，抵消IBH1影响ace的能力。因此，PRE1恢复了ace的转录活性，从而诱导细胞伸长。三拮抗bHLH蛋白，ace， IBH1和PRE1的平衡可能对确定植物细胞的大小很重要。IBH1和PRE1的表达受油菜素内酯、赤霉素和发育期依赖因子的调控，表明这一三拮抗bHLH系统整合了两种植物激素和期依赖信号。
In plants, basic helix-loop-helix (bHLH) transcription factors play important roles in the control of cell elongation. Two bHLH proteins, PACLOBTRAZOL RESISTANCE1 (PRE1) and Arabidopsis ILI1 binding bHLH1 (IBH1), antagonistically regulate cell elongation in response to brassinosteroid and gibberellin signaling, but the detailed molecular mechanisms by which these factors regulate cell elongation remain unclear. Here, we identify the bHLH transcriptional activators for cell elongation (ACEs) and demonstrate that PRE1, IBH1, and the ACEs constitute a triantagonistic bHLH system that competitively regulates cell elongation. In this system, the ACE bHLH transcription factors directly activate the expression of enzyme genes for cell elongation by interacting with their promoter regions. IBH1 negatively regulates cell elongation by interacting with the ACEs and thus interfering with their DNA binding. PRE1 interacts with IBH1 and counteracts the ability of IBH1 to affect ACEs. Therefore, PRE1 restores the transcriptional activity of ACEs, resulting in induction of cell elongation. The balance of triantagonistic bHLH proteins, ACEs, IBH1, and PRE1, might be important for determination of the size of plant cells. The expression of IBH1 and PRE1 is regulated by brassinosteroid, gibberellins, and developmental phase dependent factors, indicating that two phytohormones and phase-dependent signals are integrated by this triantagonistic bHLH system.