State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
Plant Cell Physiol. 2018 Jul 1;59(7):1415-1431. doi: 10.1093/pcp/pcy070.
Seed storage proteins (SSPs) provide free amino acids and energy for the process of seed germination. Although degradation of SSPs by the aspartic proteases isolated from seeds has been documented in vitro, there is still no genetic evidence for involvement of aspartic proteases in seed germination. Here we report that the aspartic protease ASPG1 (ASPARTIC PROTEASE IN GUARD CELL 1) plays an important role in the process of dormancy, viability and germination of Arabidopsis seeds. We show that aspg1-1 mutants have enhanced seed dormancy and reduced seed viability. A significant increase in expression of DELLA genes which act as repressors in the gibberellic acid signal transduction pathway were detected in aspg1-1 during seed germination. Seed germination of aspg1-1 mutants was more sensitive to treatment with paclobutrazol (PAC; a gibberellic acid biosynthesis inhibitor). In contrast, seed germination of ASPG1 overexpression (OE) transgenic lines showed resistant to PAC. The degradation of SSPs in germinating seeds was severely impaired in aspg1-1 mutants. Moreover, the development of aspg1-1 young seedlings was arrested when grown on the nutrient-free medium. Thus ASPG1 is important for seed dormancy, seed longevity and seed germination, and its function is associated with degradation of SSPs and regulation of gibberellic acid signaling in Arabidopsis.
种子贮藏蛋白（SSPs）为种子萌发过程提供游离氨基酸和能量。尽管已经在体外证明了从种子中分离出的天冬氨酸蛋白酶对 SSPs 的降解作用，但仍没有遗传证据表明天冬氨酸蛋白酶参与种子萌发。在这里，我们报告天冬氨酸蛋白酶 ASPG1（Guard Cell 中的天冬氨酸蛋白酶 1）在拟南芥种子的休眠、活力和萌发过程中起着重要作用。我们发现 aspg1-1 突变体具有增强的种子休眠和降低的种子活力。在 aspg1-1 种子萌发过程中，检测到作为赤霉素信号转导途径中抑制剂的 DELLA 基因的表达显著增加。aspg1-1 突变体的种子萌发对多效唑（PAC；赤霉素生物合成抑制剂）的处理更为敏感。相比之下，ASPG1 过表达（OE）转基因系的种子萌发对 PAC 表现出抗性。在 aspg1-1 突变体中，萌发种子中 SSPs 的降解严重受损。此外，当在无营养的培养基上生长时，aspg1-1 幼苗的发育被阻止。因此，ASPG1 对于种子休眠、种子寿命和种子萌发很重要，其功能与 SSPs 的降解和拟南芥中赤霉素信号的调节有关。
