State Key Laboratory of Crop Gene Resources and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
Plant Physiol. 2023 Sep 22;193(2):1580-1596. doi: 10.1093/plphys/kiad353.
Brassinosteroids play an essential role in promoting skotomorphogenesis, yet the underlying mechanisms remain unknown. Here we report that a plant-specific BLISTER (BLI) protein functions as a positive regulator of both BR signaling and skotomorphogenesis in Arabidopsis (Arabidopsis thaliana). We found that the glycogen synthase kinase 3 (GSK3)-like kinase BRASSINOSTEROID INSENSITIVE2 interacts with and phosphorylates BLI at 4 phosphorylation sites (Ser70, Ser146, Thr256, and Ser267) for degradation; in turn, BR inhibits degradation of BLI. Specifically, BLI cooperates with the BRASSINAZOLE RESISTANT1 (BZR1) transcription factor to facilitate the transcriptional activation of BR-responsive genes. Genetic analyses indicated that BLI is essentially required for BZR1-mediated hypocotyl elongation in the dark. Intriguingly, we reveal that BLI and BZR1 orchestrate the transcriptional expression of gibberellin (GA) biosynthetic genes to promote the production of bioactive GAs. Our results demonstrate that BLI acts as an essential regulator of Arabidopsis skotomorphogenesis by promoting BR signaling and GA biosynthesis.
油菜素内酯在促进暗形态建成中起着至关重要的作用，但其中的作用机制尚不清楚。在这里，我们报道了一个植物特异性的 BLISTER（BLI）蛋白作为拟南芥（Arabidopsis thaliana）中 BR 信号和暗形态建成的正调节剂。我们发现，糖原合酶激酶 3（GSK3）样激酶 BRASSINOSTEROID INSENSITIVE2 与 BLI 相互作用，并在 4 个磷酸化位点（Ser70、Ser146、Thr256 和 Ser267）处磷酸化使其降解；而 BR 则抑制 BLI 的降解。具体而言，BLI 与 BRASSINAZOLE RESISTANT1（BZR1）转录因子合作，促进 BR 响应基因的转录激活。遗传分析表明，BLI 对于 BZR1 介导的暗下胚轴伸长是必不可少的。有趣的是，我们揭示了 BLI 和 BZR1 协调赤霉素（GA）生物合成基因的转录表达，以促进生物活性 GA 的产生。我们的研究结果表明，BLI 通过促进 BR 信号和 GA 生物合成，作为拟南芥暗形态建成的重要调节剂。
