Hancock Lab


C. Nathan Hancock Laboratory

University of South Carolina Aiken
Science 205        803-641-3390         
nathanh@usca.edu

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Purpose

Plants supply the food, fiber, and fuel that are critical to human survival and quality of life. Plant domestication and breeding technology have greatly improved the yield and quality of plant products. Additional improvements in plant technology are needed to continue to meet the growing worldwide demand. Currently breeding technology, including genetic engineering, requires an understanding of which genes control important traits and how these genes function. Although crop genome sequences are now available, the functional characterization of most of the identified genes is lacking.

Background

Determination of gene function relies primarily on analysis of plants harboring mutated forms of the gene. In addition, gene function can be identified by determining the mutations responsible for a particular abnormal phenotype. The most effective strategies to induce traceable mutations involve inserting sequence "tags" into genes, allowing researchers to quickly identify which genes have been mutated. Traditional tagging studies are not feasible in most crop species because of the difficulty of transformation. Thus, we are utilizing a tagging strategy that relies on insertion of a transposable element to induce mutations.

mPing

We study a small transposable element from rice called mPing. This element has been shown to induce mutations and reach high copy number (>1000) in the genome of some rice cultivars. Our objective is to develop this element into a transposon tagging tool that can be used for gene discovery in crop species. We are performing experiments to understand mPing's transposition characteristics and testing its ability to transpose in other species.

Approach

Yeast provides a platform to quickly assess the transposition characteristics of the mPing element. In this assay, we use a reporter construct that indicates whether mPing has transposed or not. When mPing has not transposed, the cells cannot grow on plates lacking adenine, but when the genes required for mPing mobilization are expressed, mPing can be mobilized. Transposition allows growth on plates lacking adenine, producing a colony. Each colony represents a unique transposition event, thus, counting the colonies indicates the transposition frequency. By modifying the element, the mobilization proteins, or the yeast strain and measuring the effect on the transposition frequency, we can determine how these components function together.

Approach

Similarly, a transposition assay was developed in Arabidopsis. This small fast growing plant provides a platform for us to study how mPing transposition is regulated in the plant. In this assay, gfp gene is used as a reporter of mPing transposition. You only observe GFP fluorescence if mPing excises and is mobilized to a new location. These experiments take longer than the yeast, but are an important step in testing constructs for transposon tagging in crop species.

Applications

In collaboration with the University of Georgia and the University of Nebraska-Lincoln, we are assessing the transposition of mPing in soybean. Transgenic lines with active transposition have been identified and characterized. Populations of these plants have been grown out in the field and heritable phenotypes have been identified. Efforts are underway to characterize these mutants and make these resources available to the research community (see https://soymutants.uga.edu). In addition, we are preparing to test the mPing transposition in wheat.

For further information on working in Dr. Hancock's lab, contact him at 803/641-3390 or nathanh@usca.edu