Department of Life Sciences, Korea University, Seoul, Korea.
Department of Bioenergy Science and Technology, Chonnam National University, Gwangju, 61186, Korea.
Nat Commun. 2020 Feb 26;11(1):1053. doi: 10.1038/s41467-020-14905-w.
In plants, an elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, PIF4. Although PIF4 is expressed in all aerial tissues including the epidermis, mesophyll, and vascular bundle, its tissue-specific functions in thermomorphogenesis are not known. Here, we show that epidermis-specific expression of PIF4 induces constitutive long hypocotyls, while vasculature-specific expression of PIF4 has no effect on hypocotyl growth. RNA-Seq and qRT-PCR analyses reveal that auxin-responsive genes and growth-related genes are highly activated by epidermal, but not by vascular, PIF4. Additionally, inactivation of epidermal PIF4 or auxin signaling, and overexpression of epidermal phyB suppresses thermoresponsive growth, indicating that epidermal PIF4-auxin pathways are essential for the temperature responses. Further, we show that high temperatures increase both epidermal PIF4 transcription and the epidermal PIF4 DNA-binding ability. Taken together, our study demonstrates that the epidermis regulates thermoresponsive growth through the phyB-PIF4-auxin pathway.
在植物中，环境温度的升高会诱导适应性的形态变化，包括伸长的下胚轴，这主要是由 bHLH 转录因子 PIF4 调控的。虽然 PIF4 在包括表皮、叶肉和维管束在内的所有气生组织中表达，但它在热形态发生中的组织特异性功能尚不清楚。在这里，我们表明 PIF4 在表皮中的特异性表达诱导了组成型长下胚轴，而 PIF4 在脉管系统中的特异性表达对下胚轴生长没有影响。RNA-Seq 和 qRT-PCR 分析表明，生长素反应基因和生长相关基因在表皮中被高度激活，但在脉管系统中没有被激活。此外，表皮 PIF4 或生长素信号的失活，以及表皮 phyB 的过表达，都抑制了热响应性生长，表明表皮 PIF4-生长素途径对于温度响应是必不可少的。此外，我们还表明，高温增加了表皮 PIF4 的转录和表皮 PIF4 的 DNA 结合能力。总之，我们的研究表明，表皮通过 phyB-PIF4-生长素途径来调节热响应性生长。
