Novel approaches for understanding conifer seed dormancy and germination

有些种子只要遇到有利的环境条件，从亲本植物中释放出来就会立即发芽。然而，一些种子在有利的条件下无法萌发，即使它们是有活力的。这些休眠的种子必须暴露在环境信号中，如温暖干燥的条件，潮湿的冷藏，甚至是烟雾才能终止休眠。某些针叶(树)树种(如黄柏、西部白松和真冷杉)的种子产生明显的休眠，表现出扩散时萌发能力低的现象。农业和林业依赖发芽率高的种子；因此，休眠通常被认为是一种不受欢迎的特征。除了开发改进针叶种子萌发的工具外，我们还定义了一些强制和维持针叶种子休眠的因素。我们在这方面最引人注目的发现涉及发芽抑制物脱落酸(ABA)，以及一种名为ABI3的蛋白质，它有助于传递ABA信号。ABI3蛋白控制着许多对种子存活至关重要的事件。这包括食物储备的积累、休眠和种子组织对干燥的耐受性。在树木中，ABI3蛋白可能起到全球调节作用，调节其生命周期中的所有关键转变。拟议研究的目的是：(1)加深我们对ABI3在树木生命周期的重要转变中作为“守门人”的角色的理解：休眠到萌发、萌发到生长和营养生长到生殖生长(开花)的转变。(2)研究针叶树种子休眠和萌发的新调节因子。了解针叶树种深度休眠的机制将是一个重要的模型，并将产生关于这一关键适应特征所涉及的基因和蛋白质的进化保守或分化的新发现。

Some seeds germinate immediately upon their release from the parent plant as long as they encounter favorable environmental conditions. However, some seeds fail to germinate under favorable conditions, even though they are viable. These dormant seeds must be exposed to environmental cues such as periods of warm-dry conditions, moist chilling, or even smoke for dormancy to be terminated. The seeds of certain conifer (tree) species (e.g. yellow-cedar, western white pine and true firs) develop pronounced dormancy, exhibiting a low capacity for germination upon dispersal. The agricultural and forest industries rely upon seeds that exhibit high germination; hence dormancy is generally considered an undesirable trait. As well as developing tools for improving conifer seed germination, we have defined some of the factors that impose and maintain dormancy of conifer seeds. Our most striking discoveries in this regard concern the germination inhibitor abscisic acid (ABA), and a protein called ABI3, which helps to relay ABA signals. ABI3 proteins control many events that are critical to seed survival. This includes the deposition of food reserves, dormancy imposition and the acquisition of a tolerance of seed tissues to desiccation. In trees, the ABI3 protein may function as a global regulator, acting to regulate all key transitions during its lifecycle. The objectives of the proposed studies are: (1) To further our understanding of the role of ABI3 as a "gatekeeper" during important transitions of the lifecycle of trees: the dormancy-to-germination, germination-to-growth, and vegetative growth-to-reproductive growth (flowering) transitions. (2) To characterize novel regulators of dormancy and germination in conifer seeds. Understanding the mechanisms underlying the deep dormancy of conifer species will serve as an important model and will generate novel findings concerning the evolutionary conservation or divergence of genes and proteins involved in this critical adaptive trait.