Genetic Analysis of Serpentine Adaptation and Endemism

对于生物体进化和适应各种环境的过程，人们知之甚少，而生物体正是通过这种过程才产生了地球上巨大的生物多样性（包括250 000种陆生植物）。地球表面罕见和不寻常的蛇纹石（或超镁铁质）岩石的出现造成了一些最极端的陆地环境，其特征是镍和铬等有毒重金属含量高，钙、氮、磷和钾等基本矿物营养素含量极低。蛇纹岩环境的特征还在于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，但极少数植物进化出对蛇纹石的显著耐受性，这为进化适应环境提供了一个明确而令人信服的例子。为了研究蛇纹植物耐蛇纹病的遗传基础，我们建立了一个以稀有蛇纹植物抱茎蕨（Caulanthus amlexicaulis var.）barbarae和密切相关的非蛇纹植物Caulanthus amlexicaulis var. amlexicaulis（两者都是研究充分的模式植物拟南芥的近亲）。使用该系统，将通过数量性状基因座（QTL）分析来估计赋予对蛇纹石的耐受性的基因的数量和染色体位置。在未来，这些基因可以识别和特征的比较基因组学方法使用的信息，从拟南芥。 该项目将深入了解植物矿物质营养和耐旱性，这可能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种策略的关键。最后，该项目将展示研究人员如何将从大量公共投资中获得的基因组信息应用于少数模式生物，以了解世界生物多样性和适应极端复杂环境。

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.