State Key Laboratory of Crop Stress Adaptation and Improvement, Key Laboratory of Plant Stress Biology, School of Life Sciences, Henan University, Kaifeng, 475001, China.
Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, China.
J Integr Plant Biol. 2022 Apr;64(4):930-941. doi: 10.1111/jipb.13234. Epub 2022 Apr 5.
The transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) plays a crucial role in abscisic acid (ABA) signaling during seed germination. However, how ABI5 is regulated during this process is poorly understood. Here, we report that the ubiquitin E3 ligase MIEL1 and its target transcription factor MYB30 modulate ABA responses in Arabidopsis thaliana during seed germination and seedling establishment via the precise regulation of ABI5. MIEL1 interacts with and ubiquitinates ABI5 to facilitate its degradation during germination. The transcription factor MYB30, whose turnover is mediated by MIEL1 during seed germination, also interacts with ABI5 to interfere with its transcriptional activity. MYB30 functions downstream of MIEL1 in the ABA response, and both are epistatic to ABI5 in ABA-mediated inhibition of seed germination and postgerminative growth. ABA treatment induces the degradation of MIEL1 and represses the interaction between MIEL1 and ABI5/MYB30, thus releasing both ABI5 and MYB30. Our results demonstrate that MIEL1 directly mediates the proteasomal degradation of ABI5 and inhibits its activity via the release of its target protein MYB30, thus ensuring precise ABA signaling during seed germination and seedling establishment.
转录因子 ABA 不敏感 5（ABI5）在种子萌发过程中的 ABA 信号转导中发挥着关键作用。然而，ABI5 在这个过程中是如何被调控的还知之甚少。在这里，我们报告说泛素 E3 连接酶 MIEL1 及其靶转录因子 MYB30 通过精确调控 ABI5 来调节拟南芥种子萌发和幼苗建立过程中的 ABA 反应。MIEL1 与 ABI5 相互作用并泛素化 ABI5，以促进其在萌发过程中的降解。转录因子 MYB30 的周转由 MIEL1 在种子萌发过程中介导，它也与 ABI5 相互作用，干扰其转录活性。MYB30 在 ABA 反应中位于 MIEL1 的下游，并且在 ABA 介导的抑制种子萌发和萌发后生长中与 ABI5 都是上位性的。ABA 处理诱导 MIEL1 的降解，并抑制 MIEL1 与 ABI5/MYB30 之间的相互作用，从而释放 ABI5 和 MYB30。我们的结果表明，MIEL1 通过释放其靶蛋白 MYB30 直接介导 ABI5 的蛋白酶体降解并抑制其活性，从而确保种子萌发和幼苗建立过程中 ABA 信号的精确性。
