Genomic analysis of adaptation to an extreme terrestrial environment

生物已经适应了我们星球上惊人的多样性栖息地。最极端的陆地栖息地之一是地质暴露的蛇纹岩，这是地球地幔物质的化学和水文变化的产物。蛇纹石（和从这些岩石中提取的土壤）含有极其有限的一些必需的矿物质营养素，包括氮，磷，钾和钙。此外，它们天然含有高水平的有毒“重”金属，如镍和铬。由于这些多重化学挑战，蛇纹石环境的特点是土壤发育不良，有机质含量低，易受干旱影响。只有少数植物、动物和微生物的生命形式适应了严酷的蛇纹岩环境。圣巴巴拉珠宝花，C。抱茎变种枸杞是一种适应（实际上限于）蛇纹地质的芥菜科野生植物。为了研究蛇纹岩藻对蛇纹岩藻生境适应的遗传、生理和分子机制，将其与近缘种C.抱尾变种Amlexicaulis，它生长在花岗岩土壤上，在蛇纹石上显示100%的死亡率。从这个交叉的后代被用来创建一个实验群体，显示遗传分离的几个耐蛇形性状，包括低钙，低氮，低磷，以及高镍浓度的增长。这些遗传资源将沿着下一代所有表达基因测序（转录组学）和全基因组重测序，以确定适应蛇形环境的基因和遗传相互作用。蛇纹石分类群C.抱茎变种在低氮、低磷条件下，枸杞的生长上级非蛇纹石枸杞。抱茎变种抱茎了解这些遗传差异背后的分子机制，将刺激开发需要较少施用氮肥和磷肥以实现最佳产量的作物的新方法，从而有助于解决人类面临的一些最紧迫的农业环境问题：平衡全球粮食生产与过量施用氮肥和磷肥造成的污染（导致富营养化、沿海“死区”、珊瑚礁破坏和其他生态退化）。在实验室条件下，C.抱茎变种枸杞对有毒镍显示出上级耐受性，并且实际上过量积累镍至异常水平（~1%干重）。了解重金属耐受性和积累的遗传机制将提供基础科学，促进金属污染场地高效植物修复系统的开发。与一所教育创新的高中合作，该高中包括一个天然的蛇形露头，当地人口为Caulanthus amplexicaulis var。barbarae，该项目将探索一种新的模式，让学生和教师参与真正的合作研究，并与数学，空间科学，地球科学和生物学的教学相结合。

Organisms have adapted to an astonishing diversity of habitats on our planet. One of the most extreme terrestrial habitats is the result of geological exposures of serpentine rocks, which are the product of chemical and hydrological modification of materials from the Earth's mantle. Serpentine rocks (and soils derived from these rocks) have extremely limited amounts of a number of essential mineral nutrients, including nitrogen, phosphorous, potassium, and calcium. In addition, they have naturally high levels of toxic 'heavy' metals such as nickel and chromium. As a result of these multiple chemical challenges, serpentine environments are characterized by poor soil development, low levels of organic matter, and susceptibility to drought. Only a small number of plant, animal and microbial life forms have adapted to the harsh serpentine environment. The Santa Barbara Jewelflower, C. amplexicaulis var. barbarae is a wild plant in the mustard family that is adapted to (and in fact restricted to) serpentine geology. To study the genetic, physiological and molecular mechanisms that underlie adaptation to serpentine habitats, this plant was crossed to its close relative C. amplexicauis var. amplexicaulis, which grows on granite soils and shows 100% mortality on serpentine. Progeny from this cross were used to create an experimental population that showed genetic segregation for several serpentine-tolerance traits, including growth on low calcium, low nitrogen, and low phosphorous, as well as high nickel concentrations. These genetic resources will be used along with next-generation sequencing of all expressed genes (transcriptomics) and whole-genome resequencing to identify the genes and genetic interactions that underlie adaptation to the serpentine environment. The serpentine taxon C. amplexicaulis var. barbarae shows superior growth in low nitrogen and low phosphorous conditions, compared to the non-serpentine C. amplexicaulis var. amplexicaulis. Knowledge of the molecular mechanisms underlying these genetic differences will stimulate new approaches to the development of crops that require smaller applications of nitrogen and phosphorous fertilizers to achieve optimum productivity, and thus help address some of the most pressing agro-environmental issues facing humankind: balancing global food production against pollution by excess application of nitrogen and phosphorous fertilizers (leading to eutrophication, coastal 'dead zones', coral reef destruction, and other ecological degradation). Further, in laboratory experiments, C. amplexicaulis var. barbarae shows superior tolerance to toxic nickel, and actually hyper-accumulates nickel to extraordinary levels (~1% dry weight). Understanding the genetic mechanisms of heavy metal tolerance and accumulation will provide the foundational science that will foster the development of efficient phytoremediation systems for metal contaminated sites. In collaboration with an educationally innovative high school that encompasses a natural serpentine outcrop with a native population of Caulanthus amplexicaulis var. barbarae, this project will explore a new paradigm for involving students and faculty in authentic collaborative research that is integrated with teaching in mathematics, spatial sciences, earth sciences, and biology.