The role of the oxylipin OPDA in the seasonal sensitivity of seed dormancy

季节性植物生长通常始于春季萌芽或种子萌发，并在秋季至冬季的过程中随着休眠的开始而终止，这是一种公认的自然现象，可以影响全球范围内的年度大气气体交换。众所周知，环境因素如日照长度和温度直接影响植物的生长和发育，但关于植物如何利用这些因素在主要季节变化之前建立休眠却知之甚少。人们越来越有兴趣了解这些预测性反应的潜在机制，尤其是因为这些知识将帮助我们预测野生植物和作物将如何应对环境变化。我们最近取得了两个重要的发现，指向脂质信号分子，OPDA，具有核心作用，在控制种子休眠，并参与信息转移管理季节性生长控制从一代到下一代。这两个发现都是在模式植物拟南芥中发现的，但所获得的知识将适用于其他植物物种。在第一个发现中，我们发现OPDA升高是几个拟南芥突变体种子休眠增加的原因。外源OPDA的应用抑制发芽，我们有证据表明，它涉及至少一个下游目标，一个转录因子蛋白ABI 5，在OPDA的存在下增加的丰度，是必不可少的OPDA施加休眠的β-氧化突变体种子。在第二个发现中，我们发现拟南芥植物生长的日照长度对营养组织中OPDA的水平和下一代种子的休眠状态有显著影响。这种对OPDA和种子休眠的影响依赖于一种称为开花位点T（FT）的蛋白质，该蛋白质参与调节营养组织中参与OPDA合成的关键基因的表达。现在需要解决的一个主要问题是，营养组织中对日照长度的“记忆”如何传递给下一代，并表现在种子的休眠状态中。我们的初步研究表明，OPDA在从植物材料到种子的世代记忆保持中起着核心作用。此外，最近的其他研究表明，在多年生植物（如白杨）中，FT蛋白控制营养芽休眠的机制类似。我们的研究目的是通过改变营养芽和种子的休眠状态来建立环境信号影响季节性生长的机制。为了实现这一目标，我们将首先建立FT蛋白如何调节营养组织中的OPDA水平，并建立FT依赖的信息从一代转移到下一代的机制。最有可能的机制是涉及DNA的表观遗传非永久性修饰的机制，这种修饰可以影响基因表达，从而影响一代又一代的性状和表型。在这项工作的同时，我们将建立在种子发育过程中的环境信号如何影响休眠状态和OPDA水平。我们还将阐明参与OPDA介导的种子休眠控制的信号转导途径。最后，建立在我们显着的观察，在种子设置过程中经历的环境影响来自该种子的植物的生长速度，我们将调查是否涉及种子成熟环境的表观遗传OPDA依赖的记忆。这项研究的结果将影响我们预测植物生态系统如何应对环境变化的方式。它还可能影响改进农艺做法的发展，以生产休眠较少和/或生长更旺盛的作物的种子。

Seasonal plant growth, typically initiated with the onset of bud burst or seed germination in the spring and terminated with the onset of dormancy in the progression through autumn to winter, is a well recognised natural phenomenon that can affect annual atmospheric gas exchange on a global scale. Environmental cues such as day-length and temperature are well known to directly affect plant growth and development, but much less is known about how such cues are used by plants to establish dormancy in advance of major seasonal change. There is a growing interest in understanding the underlying mechanism responsible for these predictive responses, not least because such knowledge will help us to predict how wild plants and crops will respond to environmental change. We have recently made two important discoveries that point to a lipid signalling molecule, OPDA, having a central role in controlling dormancy in seeds and being involved in the transfer of information governing seasonal growth control from one generation to the next. Both of these discoveries were made in the model plant species Arabidopsis thaliana, but knowledge gained will be applicable to other plant species. In the first discovery we found that elevated OPDA is responsible for increased seed dormancy in several Arabidopsis mutants. Exogenous OPDA application inhibits germination and we have evidence to show it involves at least one downstream target, a transcription factor protein called ABI5 that increases in abundance in the presence of OPDA and is essential for the OPDA imposed dormancy in beta-oxidation mutant seeds. In the second discovery we found that the day-length in which Arabidopsis plants are grown has a dramatic effect on the levels of OPDA in vegetative tissues and the dormancy state of seeds in the next generation. This effect on OPDA and seed dormancy is dependent on a protein called Flowering Locus T (FT) that is involved in regulating expression in vegetative tissues of a key gene involved in the synthesis of OPDA. A major question that now needs to be addressed is how the 'memory' of day-length in vegetative tissues is transmitted to the next generation and manifested in the dormancy status of seeds. Our preliminary studies indicate that OPDA plays a central role in the memory retention across generations from vegetative material to seeds. Furthermore, other recent work suggests a similar mechanism involving the FT protein controls dormancy in vegetative buds in perennial species such as poplar trees. The aim of our research is to establish the mechanism by which environmental signals influence seasonal growth by modification of the dormancy state of vegetative buds and seeds. To achieve this aim we will first establish how the FT protein regulates OPDA levels in vegetative tissues and establish the mechanism by which FT-dependent information is transferred from one generation to the next. The most likely mechanism is one involving epigenetic non-permanent modification of DNA that can affect gene expression and hence traits and phenotypes from one generation to the next. In parallel with this work we will establish how environmental signals during seed development influence dormancy state and OPDA levels. We will also elucidate the signal transduction pathway involved in the OPDA mediated control of seed dormancy. Finally, building on our remarkable observation that the environment experienced during seed set influences the growth rate of plants derived from that seed, we will investigate if an epigenetic OPDA-dependent memory of the seed maturation environment is involved. The outputs of this research will impact on the way we predict how plant ecosystems respond to environmental change. It may also impact on the development of improved agronomic practice for the production of seeds that are less dormant and/or give rise to crops that grow more vigorously.