State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences, and School of Life Sciences, Peking University, Beijing 100871, China.
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.
Nat Commun. 2016 Jun 10;7:11868. doi: 10.1038/ncomms11868.
Light and gibberellins (GAs) antagonistically regulate hypocotyl elongation in plants. It has been demonstrated that DELLAs, which are negative regulators of GA signalling, inhibit phytochrome-interacting factors 3 and 4 (PIF3 and PIF4) by sequestering their DNA-recognition domains. However, it is unclear whether there are other mechanisms of regulatory crosstalk between DELLAs and PIFs. Here, we demonstrate that DELLAs negatively regulate the abundance of four PIF proteins through the ubiquitin-proteasome system. Reduction of PIF3 protein abundance by DELLAs correlates closely with reduced hypocotyl elongation. Both sequestration and degradation of PIF3 by DELLAs contribute to a reduction in PIF3 binding to its target genes. Thus, we show that promotion of PIF degradation by DELLAs is required to coordinate light and GA signals, and the dual regulation of transcription factors by DELLAs by both sequestration and degradation may be a general mechanism.
光和赤霉素（GAs）拮抗调节植物下胚轴的伸长。已经证明，作为 GA 信号负调控因子的 DELLAs 通过隔离它们的 DNA 识别结构域来抑制光敏色素相互作用因子 3 和 4（PIF3 和 PIF4）。然而，DELLAs 和 PIFs 之间是否存在其他调节串扰机制尚不清楚。在这里，我们证明 DELLAs 通过泛素-蛋白酶体系统负调控四种 PIF 蛋白的丰度。DELLAs 降低 PIF3 蛋白丰度与下胚轴伸长减少密切相关。DELLAs 对 PIF3 的隔离和降解都有助于减少 PIF3 与其靶基因的结合。因此，我们表明，DELLAs 促进 PIF 降解对于协调光和 GA 信号是必需的，并且通过隔离和降解对转录因子的双重调控可能是一种普遍机制。
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