Onion has a huge amount of DNA, more than six times the amount of humans. This enormous amount of DNA has hindered efforts to sequence the onion’s DNA and develop genomic resources for this economically important specialty crop. Pilot sequencing of the onion DNA revealed very low gene densities and long tracts of repetitive DNA, which indicates that widely used approaches to genome sequencing would be inefficient and expensive. To get around this obstacle, researchers reduced the frequency of redundant DNA by selecting against DNA with an additional methyl group attached. Methylated DNA tends to be repetitive in plant genomes.
NIFA-funded researchers at the University of Wisconsin, The J. Craig Venter Institute, and partner institutions have completed pilot sequencing of random and methyl-filtered DNA fragments from one highly inbred onion population. Their results indicate that methyl-filtration of onion DNA was very effective in reducing the proportion of both self-replicated (transposons) and anonymous sequences, and identified increased non-organellar proteins. These results are the highest so far reported for any plant and indicate that sequencing of methyl-filtered DNA fragments is an efficient approach to mapping the enormous onion genome.
This research was supported by a NIFA Initiative for Future Agricultural and Food Systems grant and
was published in October 2008
in the journal Molecular Genetics and Genomics.
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