Section of Cell and Developmental Biology and Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093, USA.
New Phytol. 2018 Jun;218(4):1534-1542. doi: 10.1111/nph.15039. Epub 2018 Feb 20.
The plant hormone auxin regulates many aspects of plant growth and development. Auxin signaling involves hormone perception by the TRANSPORT INHIBITOR RESPONSE/AUXIN F-BOX (TIR1/AFB)-Aux/IAA co-receptor system, and the subsequent degradation of the Aux/IAA transcriptional repressors by the ubiquitin proteasome pathway. This leads to the activation of downstream gene expression and diverse physiological responses. Here, we investigate how the structural elements in the Aux/IAAs determine their function in Auxin perception and transcriptional repression. We took advantage of the facile genetics of the moss Physcomitrella patens to determine the activity of wild-type and mutant PpIAA1a proteins in a Δaux/iaa null background. In this way, Aux/IAA function was characterized at the molecular and physiological levels without the interference of genetic redundancy. We identified and characterized degron variants in Aux/IAAs that affect their stability and Auxin response. We also demonstrated that neither the Aux/IAA EAR motif nor Aux/IAA oligomerization is essential for the repressive function of Aux/IAA. Our study demonstrates how key elements within the Aux/IAA proteins fine tune stability and repressor activity, as well as the long-term developmental outcome.
植物激素生长素调节植物生长和发育的许多方面。生长素信号涉及激素感知通过运输抑制剂反应/生长素 F 盒 (TIR1/AFB)-Aux/IAA 共受体系统，以及随后的生长素/IAA 转录阻遏物通过泛素蛋白酶体途径降解。这导致下游基因表达和各种生理反应的激活。在这里，我们研究了 Aux/IAAs 的结构元件如何决定它们在生长素感知和转录抑制中的功能。我们利用苔藓植物Physcomitrella patens 的简便遗传学，在Δaux/iaa 缺失背景下确定野生型和突变型 PpIAA1a 蛋白的活性。通过这种方式，在没有遗传冗余干扰的情况下，在分子和生理水平上对 Aux/IAA 功能进行了表征。我们鉴定并表征了影响 Aux/IAAs 稳定性和生长素反应的降解物变体。我们还证明，Aux/IAA 的 EAR 基序或 Aux/IAA 寡聚化对于 Aux/IAA 的抑制功能不是必需的。我们的研究表明，Aux/IAA 蛋白内的关键元件如何微调稳定性和抑制剂活性，以及长期的发育结果。
