The approaches, applied jointly in efforts to determine the gene sequences in maize, are described in the Dec. 19 issue of the journal Science. The evaluation of these methods and the assembly of the resulting sequences were undertaken by two groups led by researchers from The Institute for Genomic Research (TIGR) in Rockville, Md., and Cold Spring Harbor Laboratory in New York.
The research was funded by the National Science Foundation's Plant Genome Research Program.
Only about a quarter of the maize genome codes for genes, and these are found in small clusters scattered through a mixture of non-coding DNA and transposons (mobile DNA segments). Two different methods tested by the TIGR group successfully captured parts of the maize genome containing genes. The gene-sequences are of most interest because they provide the specific blueprint for an organism's development, structure and physiology.
With so much non-gene sequence to deal with, it has not been feasible to sequence and assemble the whole maize genome with current technologies. Thus, it is a major shortcut to capture only the portion of the maize sequence containing its genes without having to sequence the entire genome.
"Collecting the maize genes for sequencing is like panning for gold," said Jane Silverthorne, program director for NSF's plant genome program. "Just as gold can be separated from the surrounding rock because it is denser, maize genes can be separated from the surrounding DNA by their chemical and sequence properties."
The first method tested, called methylation filtration, removes sequences that contain a chemical modification (methylation) found on most of the repeated sequences and transposons, leaving behind the proverbial gold of genes.
Contact: Sean Kearns
National Science Foundation