Nitric Oxide and Regulation of Seed Dormancy

许多植物的成熟种子不容易发芽。这被称为休眠。植物育种者试图选择种子在收获前处于休眠状态，但在种植时很容易发芽的作物。它们并没有完全成功，谷类作物过早发芽仍然是一个问题。许多有害杂草的种子有很强的休眠性，在整个生长季节都不规律地萌发。因此，杂草控制很困难，这可能导致作物产量或质量严重下降。然而，休眠对于维持自然生态系统是必不可少的。由休眠种子组成的种子库持续存在于土壤中。这些种子可能会休眠多年，只有在收到适当的环境提示后才会发芽。如何控制作物和野生物种的休眠引起了人们的极大兴趣。环境条件，如光和温度，土壤硝酸盐和亚硝酸盐，燃烧植物材料产生的烟雾，以及燃烧化石燃料产生的污染物，对于打破休眠和允许种子发芽非常重要。然而，栽培或野生植物的休眠是如何建立和维持的还不得而知。提出了一种假设，即一氧化氮气体(NO)在调节农业和自然生态系统休眠中起着关键作用。拟用拟南芥和水稻这两种植物进行实验。这些实验将提供对阔叶植物和牧草休眠的深入了解。这项研究的目标是揭示种子休眠和对NO反应的生化和分子机制。需要检验的假设是，拟南芥和大麦种子可以合成NO，而且NO可以克服这两个物种种子中的休眠。用能够清除NO的化合物进行的实验也表明了内源NO在调节这些种子萌发中的作用。NO的去除加强了种子休眠，减少了种子萌发。实验表明，拟南芥和大麦种子可以从亚硝酸盐合成NO，这支持了NO在种子中作为自然调节剂的作用。有人建议使用可控气氛进行实验，以确定克服种子休眠所需的NO含量。这些实验将确定何时一氧化氮作为一种有效的休眠剂是有效的，这些信息将有助于基因发现实验的设计。还提出了其他实验来确定拟南芥种子是如何合成NO的。将使用生化和分子/遗传学的方法来研究NO如何调节拟南芥的休眠。先进的分子生物学技术将被用来监测NO处理种子的基因表达。显示休眠缺陷的种子将被用来研究NO在休眠中的作用，并发现哪些基因是休眠所必需的。这项研究的更广泛的影响包括对农业的重要性，了解如何控制有害杂草的休眠。特别是，对无控制休眠的机制的阐明可以导致操纵策略的设计。该提案还将为本科生和研究生提供培训机会，以及为高中生和K-12课程开发提供培训机会。

Mature seeds of many plants do not sprout readily. This is referred to as dormancy. Plant breeders have attempted to select for crop plants whose seeds remain dormant until harvest, yet sprout readily when planted. They have not been completely successful, and premature sprouting of cereal crops remains a problem. The seeds of many noxious weeds have strong dormancy and sprout erratically throughout the growing season. Weed control is therefore difficult, and this can result in serious reductions in crop yield or quality. Dormancy, however, is essential for the maintenance of natural ecosystems. Seed banks that consist of dormant seeds persist in soils. These seeds may lie dormant for years and will only sprout after receiving appropriate environment cues. There is great interest in how dormancy of crops and wild species is controlled. Environment conditions such as light and temperature, soil nitrates and nitrites, smoke from burning plant material, and pollutants resulting from the burning of fossil fuels are important in breaking dormancy and allowing seeds to sprout. Yet, how dormancy of cultivated or wild plants is established and maintained is unknown. A hypothesis is advanced that nitric oxide gas (NO) has a key role in regulating dormancy in agricultural and natural ecosystems. Experiments are proposed with two plants, Arabidopsis and rice. These experiments will provide insights into dormancy in broad-leaf plants and the grasses. The goals of the research are to uncover the biochemical and molecular mechanisms that underlie dormancy and the response of seeds to NO. The hypothesis to be tested is that Arabidopsis and barley seeds can synthesize NO and that NO can overcome dormancy in the seeds of both species. A role for endogenous NO in regulating germination of these seeds is also indicated by experiments with compounds that can scavenge NO. Removal of NO strengthens seed dormancy and reduces seed sprouting. Support for a role of NO as a natural regulator in seeds has come from experiments showing that Arabidopsis and barley seeds can synthesize NO from nitrite. Experiments are proposed using controlled atmospheres to determine how much NO is required to overcome dormancy in seeds. These experiments will establish when NO is effective as a dormancy-breaking agent, information that will help in the design of gene discovery experiments. Other experiments are proposed to establish how Arabidopsis seeds synthesize NO. A biochemical and molecular/genetic approach will be used to investigate how NO regulates dormancy in Arabidopsis. Advanced molecular biology techniques will be used to monitor gene expression in seeds treated with NO. Seeds showing defects in dormancy will be used to investigate how NO functions in dormancy and to discover what genes are essential for dormancy.The Broader Impacts of this research include the importance for agriculture in understanding how the dormancy of noxious weeds is controlled. In particular, an elucidation of the mechanisms by which NO controls dormancy could lead to the design of strategies of manipulation. The proposal will also provide training opportunities for undergraduate and graduate students, as well as for the training of high school students and K-12 curricular development.