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

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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.