Research in my laboratory focuses on four broad areas: (1) Genome structure and evolution, (2) construction of physical maps and the development of necessary technology for the sequencing of wheat genomes, (3) the structure of genetic variation in polyploid wheat and its relatives, and (4) genetic control of pairing and recombination between homoeologous chromosomes in wheat.
and evolution. Gene distribution along eukaryotic
chromosomes is usually heterogeneous. In wheat, the distal regions of
chromosomes tend to be gene-rich whereas the proximal regions tend to be
gene-poor. The proximal regions are enriched for genes that are present only
once in a genome (unique genes) whereas distal regions are enriched for
multigene and duplicated loci. These patterns correlate with recombination rates
in wheat genomes, which on average increase with the square of the distance of
the chromosome region from the centromere. Our studies suggest that variation in
recombination rates has played a central role in the evolution of eukaryotic
genome structure (Genome Research, 2003) .
This pivotal role of recombination in the evolution of eukaryotic chromosomes is
illustrated by the finding that the erosion of synteny along wheat homoeologous
chromosomes highly correlates with the recombination rates along chromosomes (PNAS,
2003). Genomic approaches are used in the investigation of mechanisms by
which recombination influences chromosome structure and the evolution of
Physical mapping. Physical maps are an important resource for genomic studies. The construction of physical maps for large genomes, such as those of mammals and many plants, often require fingerprinting of hundreds of thousands of large insert clones, such as BACs. In response to this need, we developed a semi-automated, high-throughput BAC fingerprint technique that makes it possible to fingerprint a thousand or more BAC clones a day. We are currently using this technique in the construction of wheat, barley, and soybean BAC contigs. Our principal goal is to develop physical maps of the 21 wheat chromosomes and to map gene distribution along them. Accomplishing these goals will set the stage for the design of a coherent sequencing strategy for wheat genomes.
Molecular variation and wheat evolution. I am the principal investigator of a large multi-institutional project focusing on the development of single nucleotide polymorphisms (SNPs) for wheat and tools for their practical exploitation. In addition to this goal, this project is examining the structure of polyploid gene pools in relation to those of diploid ancestors, the levels of nucleotide polymorphism in wheat, and the structure and distribution of nucleotide polymorphisms along chromosomes.
Genetics of recombination between wheat homoeologous chromosomes. Recombination between wheat homoeologous chromosomes is prevented by the activity of the Ph1 locus. In the absence of this gene, wheat homoeologous chromosomes recombine with disastrous consequences for fitness. The gene has been the focus of intense interest since its discovery in the 1950's because of its great significance for the meiotic stability of polyploid wheat. In the past decade, my laboratory has reported several important findings about the action of this gene. We are currently focusing on the cloning of the suppressors of the Ph1 gene via a positional cloning strategy.