State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.
Plant Cell Physiol. 2017 Nov 1;58(11):1891-1900. doi: 10.1093/pcp/pcx125.
The plant hormone auxin controls many aspects of plant growth and development by promoting the degradation of Auxin/Indole-3-acetic acid (Aux/IAA) proteins. The domain II (DII) of Aux/IAA proteins is sufficient for eliciting the degradation by directly interacting with the auxin receptor F-box protein TIR1 to form a TIR1/AFBs-Aux/IAA complex in an auxin-dependent manner. However, the underlying mechanisms of fine-tuning Aux/IAA degradation by auxin stimuli remain to be elucidated. Here, we show that OsIPK2, a rice (Oryza sativa) inositol polyphosphate kinase, directly interacts with an Aux/IAA protein OsIAA11 to repress its degradation. In a rice protoplast transient expression system, the auxin-induced degradation of Myc-OsIAA11 fusion was delayed by co-expressed GFP-OsIPK2 proteins. Furthermore, expressing additional OsIPK2 or its N-terminal amino acid sequence enhanced the accumulation of OsIAA11 proteins in transgenic plants, which in turn caused defects in lateral root formation and auxin response. Taken together, we identify a novel co-factor of Aux/IAA in auxin signaling and demonstrate its role in regulating lateral root development.
植物激素生长素通过促进Auxin/Indole-3-acetic acid（Aux/IAA）蛋白的降解来控制植物生长和发育的许多方面。Aux/IAA 蛋白的结构域 II（DII）足以通过直接与生长素受体 F-box 蛋白 TIR1 相互作用，以生长素依赖的方式形成 TIR1/AFBs-Aux/IAA 复合物，从而引发其降解。然而，生长素刺激精细调节 Aux/IAA 降解的潜在机制仍有待阐明。在这里，我们表明，水稻（Oryza sativa）肌醇多磷酸激酶 OsIPK2 直接与 Aux/IAA 蛋白 OsIAA11 相互作用，从而抑制其降解。在水稻原生质体瞬时表达系统中，共表达 GFP-OsIPK2 蛋白延迟了生长素诱导的 Myc-OsIAA11 融合蛋白的降解。此外，表达额外的 OsIPK2 或其 N 端氨基酸序列增强了转基因植物中 OsIAA11 蛋白的积累，这反过来又导致侧根形成和生长素反应缺陷。总之，我们鉴定出生长素信号转导中 Aux/IAA 的一种新的共因子，并证明其在调节侧根发育中的作用。
