Regulation of Seed Germination by GA signaling genes

本计画探讨植物激素赤霉素（GA）如何调节种子发芽、休眠及后熟。种子除了是主要的食物来源外，还能繁殖、贮藏和传播植物。种子就像植物胚胎的救生艇。至关重要的是，种子只有在允许幼苗茁壮成长和物种生存的条件下才能发芽。因此，种子萌发是由两种植物激素，脱落酸（阿坝）和GA之间的平衡微妙地调节。在胚成熟过程中，阿坝触发了一种称为种子休眠的条件，即使在有利的条件下，这种条件也会阻止种子发芽。休眠是解除一段时间的干燥储存或后熟。这种后熟的要求保证了种子随时间和空间的传播。GA刺激种子萌发，并已涉及后熟。植物如拟南芥和番茄的发芽对GA合成有绝对的要求。这个项目使用拟南芥来确定GA信号是如何被感知导致发芽的。萌发被DELLA转录因子抑制。在拟南芥中，GA通过触发DELLA RGL 2蛋白的破坏来刺激发芽。这种破坏需要GA受体GID 1和F-box蛋白质SLY 1。有趣的是，当种子长时间后熟或当GID 1受体过度产生时，萌发可以发生在产生高水平DELLA蛋白的sly 1突变体中。这表明，一种新的机制控制种子萌发和牵连GA受体。将测试三种机制：1）DELLA抑制被平行途径绕过; 2）DELLA通过与GID 1受体的相互作用而失活;以及3）DELLA通过磷酸化或泛素化而失活。阐明这些机制将通过提供分子遗传方法来改善作物幼苗建立、产量和对小麦等谷物收获前发芽的抗性，从而造福社会。有关种子生物学的知识将通过每年向华盛顿小麦种植者和小学的介绍传播。该项目将通过培训一名博士后研究员、一名本科生和一名研究生来促进教育。

This project examines how the plant hormone gibberellin (GA) regulates seed germination, dormancy, and after-ripening. Besides being a major food source, seeds propagate, store, and disperse plants. Seeds are like lifeboats for embryonic plants. It is essential that seeds germinate only under conditions that will allow the seedlings to thrive and the species to survive. Thus seed germination is exquisitely regulated by the balance between two plant hormones, abscisic acid (ABA) and GA. During embryo maturation ABA triggers a condition called seed dormancy which prevents seed germination, even under favorable conditions. Dormancy is relieved by a period of dry storage or afterripening. This requirement for after-ripening assures seed dispersal over time as well as space. GA stimulates seed germination and has been implicated in after ripening. Plants such as Arabidopsis and tomato have an absolute requirement for GA synthesis to germinate. This project uses Arabidopsis to determine how the GA signal is perceived leading to germination. Germination is repressed by DELLA transcription factors. In Arabidopsis, GA stimulates germination by triggering destruction of the DELLA RGL2 protein. This destruction requires the GA receptor GID1 and the F-box protein SLY1. Interestingly, germination can occur in sly1 mutants that produce high levels of DELLA protein when seeds have been after-ripened a long time or when the GID1 receptor is over-produced. This suggests that a new mechanism controls seed germination and implicates the GA receptor. Three mechanisms will be tested: 1) DELLA-repression is bypassed by a parallel pathway; 2) DELLA is inactivated by interaction with the GID1 receptor; and 3) DELLA is inactivated by phosphorylation or ubiquitination. Elucidating these mechanisms will benefit society by providing molecular genetic methods to improve crop seedling establishment, yield, and resistance to preharvest sprouting in cereals like wheat. Knowledge about seed biology will be disseminated through annual presentations to Washington wheat growers and elementary schools. The project will promote education through training a postdoctoral fellow, an undergraduate and graduate student.