Street Ian H, Mathews Dennis E, Yamburkenko Maria V, Sorooshzadeh Ali, John Roshen T, Swarup Ranjan, Bennett Malcolm J, Kieber Joseph J, Schaller G Eric
Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA.
Development. 2016 Nov 1;143(21):3982-3993. doi: 10.1242/dev.132035. Epub 2016 Oct 3.
Hormonal interactions are crucial for plant development. In Arabidopsis, cytokinins inhibit root growth through effects on cell proliferation and cell elongation. Here, we define key mechanistic elements in a regulatory network by which cytokinin inhibits root cell elongation in concert with the hormones auxin and ethylene. The auxin importer AUX1 functions as a positive regulator of cytokinin responses in the root; mutation of AUX1 specifically affects the ability of cytokinin to inhibit cell elongation but not cell proliferation. AUX1 is required for cytokinin-dependent changes of auxin activity in the lateral root cap associated with the control of cell elongation. Cytokinin regulates root cell elongation through ethylene-dependent and -independent mechanisms, both hormonal signals converging on AUX1 as a regulatory hub. An autoregulatory circuit is identified involving the control of ARR10 and AUX1 expression by cytokinin and auxin, this circuit potentially functioning as an oscillator to integrate the effects of these two hormones. Taken together, our results uncover several regulatory circuits controlling interactions of cytokinin with auxin and ethylene, and support a model in which cytokinin regulates shootward auxin transport to control cell elongation and root growth.
激素相互作用对植物发育至关重要。在拟南芥中，细胞分裂素通过影响细胞增殖和细胞伸长来抑制根的生长。在此，我们确定了一个调控网络中的关键机制元件，通过该网络，细胞分裂素与生长素和乙烯协同抑制根细胞伸长。生长素输入载体AUX1作为根中细胞分裂素反应的正调控因子发挥作用；AUX1突变特异性地影响细胞分裂素抑制细胞伸长的能力，但不影响细胞增殖。AUX1是侧根冠中与细胞伸长控制相关的生长素活性依赖于细胞分裂素变化所必需的。细胞分裂素通过依赖乙烯和不依赖乙烯的机制调节根细胞伸长，这两种激素信号都汇聚到AUX1作为一个调控枢纽。我们鉴定出一个自调控回路，涉及细胞分裂素和生长素对ARR10和AUX1表达的控制，该回路可能作为一个振荡器来整合这两种激素的作用。综上所述，我们的结果揭示了几个控制细胞分裂素与生长素和乙烯相互作用的调控回路，并支持了一个模型，即细胞分裂素调节向地上部的生长素运输以控制细胞伸长和根的生长。
