Oligomerization of SCFTIR1 Is Essential for Aux/IAA Degradation and Auxin Signaling in Arabidopsis.
Oligomerization of SCFTIR1 Is Essential for Aux/IAA Degradation and Auxin Signaling in Arabidopsis.
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DOI：
10.1371/journal.pgen.1006301
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发表时间：
2016-09
期刊：
影响因子：
4.5
通讯作者：
Crosby WL
中科院分区：
文献类型：
--
作者：
Dezfulian MH;Jalili E;Roberto DK;Moss BL;Khoo K;Nemhauser JL;Crosby WL
植物激素生长素是植物生长和发育的关键调节剂。拟南芥中的分子研究表明，生长素的感知和信号转导是通过TIR 1/AFB-Aux/IAA共受体介导的，TIR 1/AFB-Aux/IAA共受体组装为SCFTIR 1/AFB E3泛素连接酶复合物的一部分，并指导生长素调节的Aux/IAA转录抑制因子的降解。尽管生长素信号的重要性，很少有人知道的功能调控的TIR 1/AFB受体家族。在这里，我们表明，TIR 1可以寡聚体在植物通过一组空间聚集的氨基酸残基。虽然没有一个被鉴定的残基存在于TIR 1-Aux/IAA降解决定子的相互作用界面中，但是它们调节TIR 1与Aux/IAA底物蛋白的结合以及它们随后在体内的降解，作为生长素信号传导的一个重要方面。我们提出TIR 1的寡聚化作为一种新的调节机制，在生长素介导的植物模式和发展的调节。植物激素生长素在植物生长发育中起着多种重要作用。在拟南芥中，F-box蛋白质TIR 1是E3 SCF泛素连接酶复合物的组分，其充当生长素受体并指导生长素信号传导的阻遏物（称为Aux/IAA蛋白）的泛素依赖性降解。关于构成SCFTIR 1复合物的SKP 1、CUL 1、RBX 1和TIR 1亚基的化学计量知之甚少。在这里，我们表明，TIR 1能够在植物中寡聚化。我们还表明，突变等位基因，废除TIR 1寡聚化损害已知的SCFTIR 1底物的降解，并未能恢复生长素信号和响应的TIR 1功能丧失的遗传背景。结果表明，TIR 1同源寡聚化是SCFTIR 1功能和生长素信号转导调节的一个重要方面。
The phytohormone auxin is a key regulator of plant growth and development. Molecular studies in Arabidopsis have shown that auxin perception and signaling is mediated via TIR1/AFB–Aux/IAA co-receptors that assemble as part of the SCFTIR1/AFB E3 ubiquitin-ligase complex and direct the auxin-regulated degradation of Aux/IAA transcriptional repressors. Despite the importance of auxin signaling, little is known about the functional regulation of the TIR1/AFB receptor family. Here we show that TIR1 can oligomerize in planta via a set of spatially clustered amino acid residues. While none of the residues identified reside in the interaction interface of the TIR1-Aux/IAA degron, they nonetheless regulate the binding of TIR1 to Aux/IAA substrate proteins and their subsequent degradation in vivo as an essential aspect of auxin signaling. We propose oligomerization of TIR1 as a novel regulatory mechanism in the regulation of auxin-mediated plant patterning and development. The phytohormone auxin plays a diverse and critical role in plant growth and development. In Arabidopsis, the F-box protein TIR1 is a component of an E3 SCF ubiquitin-ligase complex that serves as the auxin receptor and directs the ubiquitin-dependent degradation of repressors of auxin signaling known as the Aux/IAA proteins. Little is known regarding the stoichiometry of the SKP1, CUL1, RBX1 and TIR1 subunits that comprise the SCFTIR1 complex. Here, we show that TIR1 is capable of oligomerization in planta. We also show that mutant alleles that abolish TIR1 oligomerization impair the degradation of known SCFTIR1 substrates and fail to restore auxin signaling and response in tir1 loss-of-function genetic backgrounds. The results suggest that TIR1 homo-oligomerization is an important aspect of the regulation of SCFTIR1 function and auxin signaling.
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