Regulation of Seed Germination by GA signaling genes

本项目研究植物激素赤霉素(GA)如何调节种子萌发、休眠和后成熟。种子除了是一种主要的食物来源外，还可以繁殖、储存和传播植物。种子就像是胚胎植物的救生艇。至关重要的是，种子只有在允许幼苗茁壮成长和物种存活的条件下才能萌发。因此，种子萌发受到两种植物激素--脱落酸(ABA)和赤霉酸(GA)之间的平衡的精确调节。在胚胎成熟期间，ABA触发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萌发。休眠可以通过一段时间的干藏或后熟来解除。这种对后熟的要求确保了种子在时间和空间上的传播。GA促进种子萌发，并与成熟后的种子萌发有关。拟南芥和番茄等植物对GA的合成有绝对的要求才能萌发。这个项目使用拟南芥来确定GA信号是如何被感知到导致萌发的。萌发受到Della转录因子的抑制。在拟南芥中，GA通过引发della RGL2蛋白的破坏来刺激萌发。这种破坏需要GA受体GID1和F-box蛋白SLY1。有趣的是，当种子长时间后熟或GID1受体过度产生时，产生高水平Della蛋白的sly1突变体可以发生萌发。这表明一种新的机制控制种子萌发，并涉及GA受体。将测试三种机制：1)Della-通过平行途径绕过抑制；2)Della通过与GID1受体相互作用失活；3)Della通过磷酸化或泛素化失活。阐明这些机制将通过提供分子遗传学方法来提高作物的成苗率、产量和对小麦等谷类作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向华盛顿小麦种植者和小学的年度报告进行传播。该项目将通过培养博士后研究员、本科生和研究生来促进教育。

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.