Genetic Analysis of Serpentine Adaptation and Endemism

人们对生物体进化和适应广泛环境的过程知之甚少，这些过程造就了地球上巨大的生物多样性(包括25万种陆地植物)。地球表面罕见和不寻常的蛇纹岩(或超镁铁质)岩石的出现导致了一些最极端的陆地环境，其特点是镍和铬等有毒重金属含量高，而钙、氮、磷和钾等基本矿物营养物质含量极低。蛇形环境的特点还包括土壤发育不良和干旱胁迫。大多数植物被排除在蛇纹石土壤之外，但极少数植物已经进化出对蛇纹石的非凡耐受性，这提供了一个清晰而令人信服的进化适应环境的例子。为了研究蛇纹草耐性的遗传基础，我们以稀有蛇纹草为材料，建立了分子遗传学实验系统。Barbarae和与其关系密切的非蛇纹石植物Caulantus pliciaulis var.Pliciaulis(两个都是研究得很好的模式植物拟南芥的近亲)。利用这一系统，将通过数量性状基因座(QTL)分析来估计与蛇纹石耐受有关的基因的数量和染色体位置。在未来，这些基因可以通过使用来自拟南芥的信息的比较基因组学方法来识别和表征。该项目将深入了解植物矿物质营养和抗旱性，这可能会对全球气候变化中的可持续农业生产力产生重大影响。此外，更好地了解植物对有毒重金属的耐受机制是金属污染环境生物修复的几个战略的关键。最后，这个项目将展示研究人员如何应用从对少数模式生物的大量公共投资中获得的基因组信息来了解世界的生物多样性和对极端和复杂环境的适应。

Little is known about the processes by which organisms evolve and adapt to a broad range of environments, giving rise to the Earth's vast biological diversity (including 250,000 species of terrestrial plants). Occurrences of the rare and unusual serpentine (or ultra-mafic) rocks on the Earth's surface give rise to some of the most extreme terrestrial environments, characterized by high levels of toxic heavy metals such as nickel and chromium, and by extremely low levels of essential mineral nutrients such as calcium, nitrogen, phosphorus and potassium. The serpentine environment is also characterized by poor soil development and drought stress. Most plants are excluded from serpentine soils, but a very few plants have evolved remarkable tolerance to serpentine, providing a clear and compelling example of evolutionary adaptation to the environment. In order to study the genetic basis of serpentine tolerance we have developed a molecular-genetic experimental system based on the rare serpentine plant Caulanthus amplexicaulis var. barbarae and the closely related non-serpentine plant Caulanthus amplexicaulis var. amplexicaulis (both close relatives of the well-studied model plant Arabidopsis thaliana). Using this system, the number and chromosomal locations of genes that confer tolerance to serpentine will be estimated by quantitative trait locus (QTL) analysis. In the future, these genes can be identified and characterized by a comparative-genomics approach using information from Arabidopsis. This project will yield insights into plant mineral nutrition and drought tolerance that may have significant implications for sustainable agricultural productivity in a changing global climate. In addition, greater understanding of the mechanisms of plant tolerance to toxic heavy metals is key to several strategies for bioremediation of metal-contaminated environments. Finally, this project will demonstrate how researchers can apply the genomic information gained from substantial public investments in a small number of model organisms toward understanding the world's biological diversity and adaptation to extreme and complex environments.