Ithaca, New York
Cornell University
Mystic Connecticut
Monsanto Company
Regional mutagenesis utilizing Activator (Ac) in maize --Conrad, L, Hardeman, K, Lewis, P, Lebjko, S, Farmer, P, Ahern, K, Chomet, P, Brutnell, T As demonstrated in numerous studies, the Ac/Ds family of transposable elements can serve as powerful mutagens in the cloning and characterization of genes (see Dellaporta and Moreno in: The Maize Handbook, pp. 219-233, 1994). Nevertheless, the propensity of Ac for short-range transposition has limited its use in genome-wide mutagenesis experiments. The comprehensive goal of this NSF-funded Plant Genome Research project is to overcome this limitation and provide the maize research community with a series of Ac-containing lines for use in regional mutagenesis. We are in the process of creating a collection of approximately 200 near-isogenic lines each containing a single active anchor Ac (aAc). Each aAc will be positioned on publicly available recombinant inbred populations to identify those elements at roughly 10 cM intervals throughout the entire genome. Importantly, the maintenance of this Ac population in a well-characterized genetic inbred, W22, will permit screens for subtle phenotypic changes associated with Ac insertion. These phenotypes are likely to arise when a single gene contributing to a multigenic quantitative trait is disrupted or when a single member of a multigene family is inactivated. In addition, it will be possible to exploit the tendency of Ac to move to linked sites to create an allelic series of a target gene.

To date, we have cloned sequences flanking 64 Ac elements and confirmed 39 as linked to an active, germinally-inherited Ac element. We have placed 18 on the genetic map, and are continually cloning, mapping, and generating additional active Acís at unique locations throughout the genome (Figure 1).

Figure 1.

In addition to the development of the technology and protocols for regional mutagenesis, we plan to calculate the efficiency of localized Ac-mutagenesis. Utilizing several aAc lines positioned on chromosome 1, we are generating transpositions and screening the F2 progeny for Ac- induced mutations. This will allow us to determine the frequency of Ac-induced mutations and to examine the relationship between proximity of a target locus and the donor Ac line.

Finally, an important objective of this project is to develop a summer genetics program involving senior researchers, graduate students, undergraduate students, high school teachers, and high school students. This program is designed to facilitate interactions between often isolated groups in both research and education. It is our hope that this will give researchers a chance to familiarize themselves with the use of these aAc lines, while at the same time educating young students about maize genetics, and increasing the public understanding of science. The Emerson Summer Genetics Program officially began in June 2001. The participants included: five high school students (local and national), one high school teacher, three undergraduates (local and international), two post-docs, two graduate students, and two senior researchers. The participants cooperated on various projects in the field and lab and have developed a web site detailing the program activities at: (http://bti.cornell.edu /Brutnell_lab2/Projects/ESGP/ESGP-Program.html). Importantly, the students participating in this program helped generate 3,000 transpositions from Acís positioned on chromosome 1 that will be used in determining the frequency of Ac-induced mutations.
 
 


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