Identification and Characterization of Mutations that can be used to Engineer Aluminum Tolerance in Agriculturally Relevant Plants.

酸性土壤中的铝（Al）毒性严重限制了全球农业，因为世界上30%以上的可耕地被认为具有抑制根系生长从而抑制作物产量的铝水平。铝有毒土壤在世界上由许多发展中国家组成的热带地区特别普遍。目前对铝的毒性以及一些植物如何在其环境中抵抗或耐受铝的了解仍然有限。通过进一步了解铝毒性和抗性的机制，可以开发出在铝毒性环境中生长和茁壮成长的作物基因工程的新策略。拟南芥已被植物科学家用作确定植物基因功能的模式遗传系统，并随后将这些基因与植物生命周期中的特定现象联系起来。虽然不是作物物种，但拟南芥的独特优势使科学家能够迅速将基因归因于特定功能，为植物生长发育的各个方面提供坚实的知识基础。这也适用于鉴定植物在恶劣环境（包括铝中毒土壤）中生长所依赖的基因。利用诱变方法，即引入破坏基因功能的核苷酸变化，已经确定了植物在铝中毒环境中生长所需的基因产物。这些Al （Al敏感）突变在缺Al的情况下对拟南芥的生长影响不大，但在有Al的情况下会导致极端的根生长抑制。其中一种als突变体，als1 -1，其表型提供了一个独特的机会，使用抑制因子分析来识别在Al存在下赋予生长能力增加的遗传变化。对于抑制因子方法，als1 -1突变体遭受随机突变。据预测，这将产生一小部分突变植物亚群，这些突变植物的遗传变化掩盖了als3-1表型，并恢复了als3-1根在Al存在下的生长能力。使用这种方法，鉴定了12个als3-1抑制突变体，它们不仅逆转了als3-1突变的影响，而且使根的生长能力远远大于野生型未突变的拟南芥植物。本项目的目的是分离这些突变，并确定为什么它们在存在铝的情况下比野生型根系生长得更好。最终，分离的突变将被单独或组合引入模式作物物种，以确定它们是否对工程作物有用，这些作物可以在目前由于铝毒性而无法维持重要农业的地区生长。更广泛的影响：这项工作不仅在制定解决铝毒性问题的策略方面有希望，而且为未来的科学家提供了一个极好的培训机会。来自美国国家科学基金会资助的加州少数民族参与联盟（CAMP）， UCR指导暑期研究实习计划（MSRIP）和UCR哥白尼项目（旨在增加加州少数民族高中科学教师的数量）的学生现在和将来都将积极参与该项目。这些学生将由项目主任和一名博士后直接指导，博士后也将通过参与本项目进行培训。有了这个机会，代表性不足的群体将得到方法和理论方面的培训，使他们有能力从事科学事业，解决他们这一代人所面临的问题。

Aluminum (Al) toxicity in acidic soils severely limits global agricultural since more than 30% of the world's arable land is considered to have levels of Al that are inhibitory to root growth and consequently crop yield. Al toxic soils are particularly common in the world's tropical regions, which are comprised of many of the world's developing countries. The current understanding of Al toxicity and how some plants can either resist or tolerate Al in their environment remains limited. By gaining further knowledge of the mechanisms underlying Al toxicity and resistance, new strategies for genetic engineering of crop plants that can grow and thrive in an Al toxic environment can be developed. Arabidopsis thaliana has been used by plant scientists as a model genetic system to determine the function of plant genes and subsequently link these to particular phenomena in a plant's life cycle. Although not a crop species, Arabidopsis' unique advantages have allowed scientists to quickly attribute genes to specific functions, giving a solid knowledge base regarding all aspects of plant growth and development. This is also true for identification of genes that plants rely on for growth in inhospitable environments, including Al toxic soils. Using a mutagenesis approach, whereby nucleotide changes that disrupt gene function are introduced, genes whose products are required by plants for growth in an Al toxic environment have been identified. These als (Al sensitive) mutations have little effect on growth of Arabidopsis in the absence of Al, but result in extreme root growth inhibition when Al is present.One of the als mutants, als3-1, has a phenotype that offers a unique opportunity using suppressor analysis to identify genetic changes that confer increased growth capability in the presence of Al. For the suppressor approach, the als3-1 mutant was subjected to random mutagenesis. This was predicted to generate a small sub-population of mutant plants that have genetic changes that mask the als3-1 phenotype and restore the capability of als3-1 roots to grow in the presence of Al. Using this approach, twelve als3-1 suppressor mutants were identified that not only reverse the effects of the als3-1 mutation but also give root growth capability that is far greater than what is found for wild type, unmutagenized Arabidopsis plants. The purpose of the present project is to isolate these mutations and to determine why they confer greater than wild type root growth in the presence of Al. Ultimately, the isolated mutations will be introduced into model crop species either singly or in combination in order to determine if they will be useful for engineering crops that can grow in regions that currently cannot sustain significant agriculture due to Al toxicity.Broader Impacts: Not only does this work have promise with regard to developing strategies for addressing the issue of Al toxicity, it also represents an excellent training opportunity for future scientists. Students from NSF-funded California Alliance for Minority Participation (CAMP), the UCR Mentoring Summer Research Internship Program (MSRIP), and the UCR Copernicus project, which seeks to increase the number of minority high school science teachers in California, are currently and will in the future be active participants in this project. These students will be directly mentored by the project director and a post-doctoral associate, who will also be trained through participation in this project. By having this opportunity, underrepresented groups will be given both methodological and theoretical training that will give them the ability to pursue careers in science for addressing and solving concerns that are presented to their generation.