Fu Weihao, Shen Juan, He Liming, Wang Ling, Li Jia, Chang Jinke
Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
Guangdong Provincial Key Laboratory of Plant Adaptation and Molecular Design, School of Life Sciences, Guangzhou University, Guangzhou 510006, China.
Plant Physiol. 2025 Mar 28;197(4). doi: 10.1093/plphys/kiaf129.
Roots exhibit hydrotropism in response to moisture gradients to avoid drought stress. Several proteins have been reported to regulate this process, with MIZU-KUSSEI 1 (MIZ1) being identified as a pivotal regulator. Although most studies on the regulatory mechanisms of root hydrotropism have focused on MIZ1, the molecular mechanisms of MIZ1 are poorly understood. Here, we report that MIZ1 plays an essential role in regulating cytokinin signal transduction by interacting with cytokinin receptors, ARABIDOPSIS HISTIDINE KINASEs (AHKs), in Arabidopsis (Arabidopsis thaliana). The miz1-2 mutant exhibited a decreased response to cytokinins, whereas overexpressors of MIZ1 showed an increased response to cytokinins. The expression levels of 2 Type-A Arabidopsis response regulators (ARRs) of cytokinins, ARR16 and ARR17, were downregulated, and their upregulation by cytokinins was substantially attenuated in miz1-2 compared with those in Col-0. Overexpression of MIZ1 partially rescued the decreased response of the ahk2-5 ahk3-7 double mutant to cytokinins. MIZ1 can physically interact with AHKs, as revealed by yeast 2-hybrid, bimolecular fluorescence complementation (BiFC), and co-immunoprecipitation (co-IP) assays. Mutants of cytokinin signal transduction, such as ahk2-5 ahk3-7 ahk4-2 and arr3 arr4 arr5 arr6 arr8 arr9 arr16-C arr17-C, showed a greatly reduced hydrotropic response, similar to miz1-2. Additionally, MIZ1 also regulates the homeostasis of cytokinins by controlling the expression of genes encoding their biosynthetic and catabolic enzymes. Our results reveal the critical role of MIZ1 in regulating the cytokinin signaling response, which is essential for the root hydrotropic response.
根会响应水分梯度表现出向水性，以避免干旱胁迫。据报道，有几种蛋白质参与调控这一过程，其中水势感应蛋白1（MIZ1）被确定为关键调节因子。尽管大多数关于根向水性调控机制的研究都聚焦于MIZ1，但其分子机制仍知之甚少。在此，我们报道MIZ1在拟南芥中通过与细胞分裂素受体拟南芥组氨酸激酶（AHK）相互作用，在调控细胞分裂素信号转导中发挥着重要作用。miz1-2突变体对细胞分裂素的反应减弱，而MIZ1过表达植株对细胞分裂素的反应增强。细胞分裂素的2个A型拟南芥反应调节因子（ARR），即ARR16和ARR17的表达水平下调，与Col-0相比，miz1-2中细胞分裂素对它们的上调作用显著减弱。MIZ1过表达部分挽救了ahk2-5 ahk3-7双突变体对细胞分裂素反应减弱的现象。酵母双杂交、双分子荧光互补（BiFC）和免疫共沉淀（co-IP）分析表明，MIZ1能与AHK发生物理相互作用。细胞分裂素信号转导突变体，如ahk2-5 ahk3-7 ahk4-2和arr3 arr4 arr5 arr6 arr8 arr9 arr16-C arr17-C，表现出与miz1-2类似的大幅减弱的向水反应。此外，MIZ1还通过控制编码其生物合成和分解代谢酶的基因表达来调节细胞分裂素的稳态。我们的结果揭示了MIZ1在调控细胞分裂素信号反应中的关键作用，这对根的向水反应至关重要。
