The Physiological Basis of Natural Variation in Germination Responses of Arabidopsis Thaliana

拟南芥萌发响应自然变异的生理基础在拟南芥和许多其他物种的生命周期中，两个发育开关决定了整个生活史和随之而来的种群生物学：萌发开关和开花开关。关于开花时间适应的相关基因、开花的分子遗传途径和开花时间自然变异的地理分布，我们已经了解得很多。研究萌发时间的类似努力有可能对整个生活史时间表的适应和种群变异的遗传基础提供重要的见解。因此，本研究的重点是发芽时间的遗传基础和进化生态学。最近发现，光感受器基因家族，即光敏色素，在发芽过程中具有重要的功能，可能使它们能够调节发芽的季节。新的数据表明光敏色素既参与萌发，也参与其相反的性状：休眠。此外，不同光敏色素对种子萌发的贡献取决于温度。本研究将通过突变体研究来检验光敏色素是否能调控种子萌发温度，比较不同光敏色素突变体的基因表达，并检验种子萌发的自然变异是否涉及这些相同途径的表达变异。对发芽反应自然变化的地理分析将在区域尺度上检验自然选择对发芽的影响。除了测试光敏色素调控发芽的基本机制外，拟议的研究还将测试光敏色素调控的发芽途径的自然变化，并测试这种自然变化是由于光敏色素调控基因的表达变化还是由于光敏色素序列本身的变化。这些对发芽响应的遗传基础和发芽变异的地理分布的研究，将有助于我们理解随着环境变化而发生的范围扩展和分布变化的过程。通过结合开花时间和发芽物候的建模，目标是预测生活史和人口统计作为不断变化的环境条件的函数。表型调查和微阵列研究的结果将向社区提供，并为未来发芽自然变异的遗传基础研究奠定基础。这项研究还支持在基因组、生理和计算技术的各个层面上的国际合作和培训。

The physiological basis of natural variation in germination responses of Arabidopsis thalianaIn the life cycle of Arabidopsis thaliana and many other species, two developmental switches determine overall life history and consequent population biology: the switch to germination and the switch to flowering. Much is known about genes associated with adaptation in flowering time, molecular genetic pathways of flowering, and geographic distribution of natural variation in flowering time. Comparable effort devoted to understanding germination timing has the potential to provide significant insight into adaptation of entire life history schedules and the genetic basis of population variation. This research therefore focuses on the genetic basis and evolutionary ecology of germination timing. It has recently been found that the gene family of photoreceptors, the phytochromes, have important functions during germination that may give them the ability to regulate the season of germination. New data indicate that phytochromes are involved in both germination and its opposite trait: dormancy. Moreover, contributions of different phytochromes to germination depend on temperature. This research will test whether phytochrome can regulate the temperature of germination through mutant studies, compare gene expression in different phytochrome mutants, and test whether natural variation in germination involves variation in the expression of these same pathways. A geographic analysis of natural variation in germination responses will test for evidence of natural selection on germination on a regional scale. In addition to testing fundamental mechanisms of phytochrome regulation of germination, the proposed research will test for natural variation in the germination pathways regulated by phytochromes and test whether that natural variation is due to variation in expression of phytochrome-regulated genes or due to variation in phytochrome sequence itself. These studies of the genetic basis of germination responses and the geographic distribution of variation in germination will contribute significantly to our understanding of processes of range expansion and distributional changes accompanying environmental change. By combining modeling of flowering time and germination phenology, the goal is to predict life history and demography as a function of changing environmental conditions. Results of the phenotypic survey and microarray studies will be made available to the community and provide a foundation for future studies of the genetic basis of natural variation in germination. This research also supports international collaboration and training at various levels in genomic, physiological, and computational techniques.