College of Life Sciences, Capital Normal University, and Beijing Key Laboratory of Plant Gene Resources and Biotechnology for Carbon Reduction and Environmental Improvement, Beijing 100048, China.
State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, and School of Life Sciences, Peking University, Beijing 100871, China.
Curr Biol. 2024 Jul 22;34(14):3152-3164.e6. doi: 10.1016/j.cub.2024.06.014. Epub 2024 Jul 5.
Seed germination represents a determinant for plants to enter ecosystems and is thus regarded as a key ecological and agronomic trait. It is tightly regulated by a variety of environmental cues to ensure that seeds germinate under favorable conditions. Here, we characterize BBX32, a B-box zinc-finger protein, as an imbibition-stimulated positive regulator of seed germination. Belonging to subgroup V of the BBX family, BBX32 exhibits distinct characteristics compared with its close counterparts within the same subgroup. BBX32 is transiently induced at both the transcriptional and post-transcriptional levels in the embryo upon water absorption. Genetic evidence indicates that BBX32 acts upstream of the master transcription factor PHYTOCHROME-INTERACTING FACTOR 1 (PIF1) to facilitate light-induced seed germination. BBX32 directly interacts with PIF1, suppressing its protein-interacting and DNA-binding capabilities, thereby relieving PIF1's repression on seed germination. Furthermore, the imbibition-stimulated BBX32 functions in parallel with the light-induced transcription regulator HFR1 to collectively attenuate the transcriptional activities of PIF1. The BBX32-PIF1 de-repression module serves as a molecular connection that enables plants to integrate signals of water availability and light exposure, effectively coordinating the initiation of seed germination.
种子萌发是植物进入生态系统的决定因素，因此被认为是一个关键的生态和农艺性状。它受到各种环境线索的严格调控，以确保种子在有利条件下萌发。在这里，我们将 BBX32 鉴定为一种吸胀刺激的种子萌发正调控因子，它是一种 B 盒锌指蛋白。属于 BBX 家族的亚组 V，与同一亚组内的密切对应物相比，BBX32 表现出独特的特征。在吸收水分后，BBX32 在胚胎中同时在转录和转录后水平上短暂诱导。遗传证据表明，BBX32 在上游作用于主转录因子 PHYTOCHROME-INTERACTING FACTOR 1（PIF1），以促进光诱导的种子萌发。BBX32 直接与 PIF1 相互作用，抑制其蛋白相互作用和 DNA 结合能力，从而解除 PIF1 对种子萌发的抑制。此外，吸胀刺激的 BBX32 与光诱导的转录调节剂 HFR1 平行发挥作用，共同减弱 PIF1 的转录活性。BBX32-PIF1 去阻遏模块作为一种分子连接，使植物能够整合水分可用性和光照暴露的信号，有效地协调种子萌发的启动。
