Functional Genomics of Maize Centromeres

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PI: R. Kelly Dawe (University of Georgia-Athens) Co-PIs: James A. Birchler (University of Missouri-Columbia) and Jiming Jiang (University of Wisconsin-Madison) All plant genomes contain centromeres, structural regions that ensure chromosomes segregate properly during cell division. Centromeres are a challenge to study because they contain repetitive DNA sequences and few genes. The goal of this project is to develop an understanding of how the sequences in centromeres relate to their function, and how changes in centromere size or changes in a key centromere binding protein (CENH3) can alter the behavior of centromeres. In particular the project will study genetic crosses and mutants that can induce centromere failure and chromosome loss in hybrids. Chromosome loss induced by centromere modification can result in haploid plants, which are of great value to corn breeders, as they can rapidly accelerate the production of new inbred lines. It is anticipated that the information and technology generated will have direct applications to agriculture - not only in maize but all other crops that utilize haploids as a breeding tool. With regards to training and outreach, the project will provide research training for undergraduate and graduate students as well as postdoctoral fellows in plant genomics and biotechnology. In addition, a series of training workshops will be held to disseminate techniques and materials generated in this project. All project outcomes will be made available to the research community through a dedicated project web site and through dissemination by long-term repositories that include NCBI, MaizeGDB and Gramene. The overall goals of the project are to understand the genetic and epigenetic components of maize centromeres and to reveal the role of centromere size in uniparental chromosome elimination which leads to haploid formation. The specific objectives are to: 1) determine whether common centromere repeat sequences are sufficient to induce centromere function using novel chromosome painting probes, chromosome visualization tools that dramatically improve the ability to detect changes in chromosome structure; 2) determine how a suite of chromatin markers are affected by changes in centromere size and location using maize chromosomes transferred into oat as well as B chromosomes that have undergone a cycle of inactivation and reactivation; 3) test whether centromere size disparity can cause uniparental genome elimination by screening lines with centromeres whose size have been modified by manipulating genome size, and by using cenh3 mutants with specialized transgenes; and 4) determine how maize centromeres behave in situations of uniparental genome elimination, particularly in wheat X maize and oat X maize crosses that are regularly used in haploid breeding schemes.