Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Comparative-Sequence And Genetic Analyses Of The Asparagus, Onion, And Rice Reveal Similar Structures, But No Microsynteny

Michael J. Havey¹ , Jernej Jakse² , Foo Cheung³ , Go Suzuki⁴ , John McCallum⁵ , Christopher D. Town³

¹  Agricultural Research Service, USDA, Dep. of Horticulture, 1575 Linden Drive, University of Wisconsin, Madison, WI 53706 USA

²  Agronomy Department, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, Ljubljana 1000, Slovenia

³  The Institute for Genomic Research, 9712 Medical Center Dr., Rockville, MD 20850 USA

⁴  Laboratory of Plant Molecular Genetics, Division of Natural Science, Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, 582-8582 Osaka, Japan

⁵  Crop & Food Research, Private Bag 4704, Christchurch, New Zealand

The Poales (includes the grasses) and Asparagales [includes onion (Allium cepa) and asparagus (Asparagus officinalis)] are the two most economically important monocot orders. Comparative genomic analyses among the grass genomes revealed a high degree of synteny; however it is not known if this synteny extends to other major monocot groups with enormous variation for genome sizes, such as the Asparagales. We sequenced asparagus and onion BACs and observed long tracts of degenerated retroviral elements and transposons similar to other larger plant genomes. As expected, gene densities in asparagus and onion were less than the smaller grass genomes. Physically linked sequences on the asparagus BACs showed significant similarities to rice genes on different chromosomes, revealing no microsynteny between asparagus and rice across the sequenced regions. Physically linked asparagus sequences were used to select highly similar (e<-20) expressed sequence tags of onion, which mapped to different onion chromosomes and no relationship was observed between physical linkages in asparagus and genetic linkages in onion. These results demonstrate that the smaller genomes of rice and asparagus are not appropriate models for the enormous nuclear genome of onion, and that genomic resources must be independently developed for the Alliums.