Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria.
Department of Plant Physiology and Biotechnology, Nicolaus Copernicus University in Toruń, Toruń, Poland.
Nature. 2022 Nov;611(7934):133-138. doi: 10.1038/s41586-022-05369-7. Epub 2022 Oct 26.
The phytohormone auxin is the major coordinative signal in plant development, mediating transcriptional reprogramming by a well-established canonical signalling pathway. TRANSPORT INHIBITOR RESPONSE 1 (TIR1)/AUXIN-SIGNALING F-BOX (AFB) auxin receptors are F-box subunits of ubiquitin ligase complexes. In response to auxin, they associate with Aux/IAA transcriptional repressors and target them for degradation via ubiquitination. Here we identify adenylate cyclase (AC) activity as an additional function of TIR1/AFB receptors across land plants. Auxin, together with Aux/IAAs, stimulates cAMP production. Three separate mutations in the AC motif of the TIR1 C-terminal region, all of which abolish the AC activity, each render TIR1 ineffective in mediating gravitropism and sustained auxin-induced root growth inhibition, and also affect auxin-induced transcriptional regulation. These results highlight the importance of TIR1/AFB AC activity in canonical auxin signalling. They also identify a unique phytohormone receptor cassette combining F-box and AC motifs, and the role of cAMP as a second messenger in plants.
植物激素生长素是植物发育过程中的主要协调信号，通过已建立的经典信号通路介导转录重编程。运输抑制剂反应 1（TIR1）/生长素信号 F -box（AFB）生长素受体是泛素连接酶复合物的 F -box 亚基。在生长素的响应下，它们与Aux/IAA 转录抑制剂结合，并通过泛素化将其靶向降解。在这里，我们确定腺苷酸环化酶（AC）活性是跨陆地植物 TIR1/AFB 受体的另一个功能。生长素与 Aux/IAAs 一起刺激 cAMP 的产生。TIR1 C 端区域的 AC 基序中的三个独立突变，都消除了 AC 活性，使 TIR1 无法介导向重力性和持续的生长素诱导的根生长抑制，也影响生长素诱导的转录调控。这些结果强调了 TIR1/AFB AC 活性在经典生长素信号中的重要性。它们还确定了一个独特的植物激素受体盒，结合了 F 盒和 AC 基序，以及 cAMP 作为植物中第二信使的作用。
