Protein degradation is essential in plant growth and development. The stability of Cullin3 substrate adaptor protein BPM1 is regulated by multiple environmental cues pointing on manifold control of targeted protein degradation. A small family of six MATH-BTB genes (BPM1-6) is described in Arabidopsis thaliana. BPM proteins are part of the Cullin E3 ubiquitin ligase complexes and are known to bind at least three families of transcription factors: ERF/AP2 class I, homeobox-leucine zipper and R2R3 MYB. By targeting these transcription factors for ubiquitination and subsequent proteasomal degradation, BPMs play an important role in plant flowering, seed development and abiotic stress response. In this study, we generated BPM1-overexpressing plants that showed an early flowering phenotype, resistance to abscisic acid and tolerance to osmotic stress. We analyzed BPM1-GFP protein stability and found that the protein has a high turnover rate and is degraded by the proteasome 26S in a Cullin-dependent manner. Finally, we found that BPM1 protein stability is environmentally conditioned. Darkness and salt stress triggered BPM1 degradation, whereas elevated temperature enhanced BPM1 stability and accumulation in planta.

中文翻译：

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拟南芥 BPM1 的蛋白质周转参与调控开花时间和非生物胁迫反应。

蛋白质降解对植物的生长和发育至关重要。Cullin3 底物衔接蛋白 BPM1 的稳定性受到多种环境线索的调节，这些环境线索指向目标蛋白质降解的多种控制。在拟南芥中描述了一个由六个 MATH-BTB 基因 (BPM1-6) 组成的小家族。BPM 蛋白是 Cullin E3 泛素连接酶复合物的一部分，已知可结合至少三个转录因子家族：ERF/AP2 I 类、同源盒-亮氨酸拉链和 R2R3 MYB。通过靶向这些转录因子进行泛素化和随后的蛋白酶体降解，BPM 在植物开花、种子发育和非生物胁迫反应中发挥着重要作用。在这项研究中，我们产生了 BPM1 过表达的植物，这些植物表现出早期开花表型、对脱落酸的抗性和对渗透胁迫的耐受性。我们分析了 BPM1-GFP 蛋白质的稳定性，发现该蛋白质具有高周转率，并被蛋白酶体 26S 以 Cullin 依赖性方式降解。最后，我们发现 BPM1 蛋白的稳定性受环境影响。黑暗和盐胁迫引发 BPM1 降解，而升高的温度增强了 BPM1 在植物中的稳定性和积累。