Brassinosteroids Dominate Hormonal Regulation of Plant Thermomorphogenesis via BZR1
Brassinosteroids Dominate Hormonal Regulation of Plant Thermomorphogenesis via BZR1
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DOI：
10.1016/j.cub.2017.11.077
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发表时间：
2018-01-22
期刊：
影响因子：
9.2
通讯作者：
Quint, Marcel
中科院分区：
文献类型：
--
作者：
Ibanez, Carla;Delker, Carolin;Quint, Marcel
热形态建成被定义为一系列形态变化，这些变化共同可能有助于适应性生长适应通常升高的环境温度[1，2]。虽然温暖诱导的信号转导的许多细节仍然难以捉摸，但与光信号传导的相似之处最近变得明显（在[3]中综述）。它涉及光感受器，也可以感知环境温度的变化[3-5]，并通过抑制温度信息的中心整合者植物色素相互作用因子4（PIF 4）的蛋白质活性来发挥作用[6]。此外，PIF 4转录物的积累受到夜间复合体成员EARLY FLOWARLY 3的严格控制[7，8]。根据目前的理解，PIF 4直接激活生长促进基因，但也通过诱导生长素生物合成和信号传导，导致细胞伸长。基于突变筛选的模式植物拟南芥的突变体与温度诱导下胚轴伸长的缺陷，我们在这里表明，PIF 4和生长素的功能依赖于油菜素类固醇。遗传和药理学分析将油菜素类固醇置于PIF 4和生长素的下游。我们发现油菜素类固醇通过转录因子油菜素耐药1（BZR 1）起作用，该转录因子在高温下积累在细胞核中，在那里它诱导生长促进基因的表达。此外，我们表明，在高温下BZR 1结合到PIF 4的启动子，诱导其表达。这些发现表明，BZR 1在参与PIF 4激活的放大前馈回路中发挥作用。尽管已经描述了许多PIF 4的负调控因子，但我们在这里将BZR 1确定为PIF 4的真正温度依赖性正调控因子，作为主要的生长协调剂。
Thermomorphogenesis is defined as the suite of morphological changes that together are likely to contribute to adaptive growth acclimation to usually elevated ambient temperature [1, 2]. While many details of warmth-induced signal transduction are still elusive, parallels to light signaling recently became obvious (reviewed in [3]). It involves photoreceptors that can also sense changes in ambient temperature [3-5] and act, for example, by repressing protein activity of the central integrator of temperature information PHYTOCHROME-INTERACTING FACTOR 4 (PIF4 [6]). In addition, PIF4 transcript accumulation is tightly controlled by the evening complex member EARLY FLOWERING 3 [7, 8]. According to the current understanding, PIF4 activates growth-promoting genes directly but also via inducing auxin biosynthesis and signaling, resulting in cell elongation. Based on a mutagenesis screen in the model plant Arabidopsis thaliana for mutants with defects in temperature-induced hypocotyl elongation, we show here that both PIF4 and auxin function depend on brassinosteroids. Genetic and pharmacological analyses place brassinosteroids downstream of PIF4 and auxin. We found that brassinosteroids act via the transcription factor BRASSINAZOLE RESISTANT 1 (BZR1), which accumulates in the nucleus at high temperature, where it induces expression of growth-promoting genes. Furthermore, we show that at elevated temperature BZR1 binds to the promoter of PIF4, inducing its expression. These findings suggest that BZR1 functions in an amplifying feedforward loop involved in PIF4 activation. Although numerous negative regulators of PIF4 have been described, we identify BZR1 here as a true temperature-dependent positive regulator of PIF4, acting as a major growth coordinator.