ARS | Publication request: A One-Megabase Physical Map Provides Insights on Gene Organization in the Enormous Mitochondrial Genome of Cucumber

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2009
Publication Date: April 30, 2009
Citation: Bartoszewski, G., Gawronski, P., Szklarczyk, M., Verbakel, H., Havey, M.J. 2009. A One-Megabase Physical Map Provides Insights on Gene Organization in the Enormous Mitochondrial Genome of Cucumber. Genome. 52:299-307.

Interpretive Summary: Cucumber has one of the largest mitochondrial DNAs known among all plants and animals, due in part to the accumulation of short repetitive DNAs. Recombination among these repetitive DNAs produces rearrangements that negatively affect mitochondrial gene expression. In order to more efficiently identify rearrangements in the cucumber mitochondrial DNA, we built two non-overlapping 800 and 220 kilobase DNAs and assigned major mitochondrial genes to these DNAs. Mitochondrial genes were distributed across the regions and often were separated by long physical distances, although occasional clustering was observed. Non-coding regions (inrons) in the nad1, nad4, and nad7 genes were larger than those reported in other plants, indicating that increased intron sizes also contributed to mitochondrial DNA expansion in cucumber. These cloned DNAs will be useful for geneticists for the eventual sequencing of the cucumber mitochondrial DNA, which can be exploited to more efficiently screen for unique rearrangements affecting mitochondrial gene expression.

Technical Abstract: Cucumber has one of the largest mitochondrial genomes known among all eukaryotes, due in part to the accumulation of short repetitive-DNA motifs. Recombination among these repetitive DNAs produces rearrangements affecting organization and expression of mitochondrial genes. In order to more efficiently identify rearrangements in the cucumber mitochondrial DNA, we built two non-overlapping 800 and 220 kb BAC contigs and assigned major mitochondrial genes to these BACs. Polymorphism carried on the largest BAC contig was used to confirm paternal transmission. Mitochondrial genes were distributed across BACs and physically distant, although occasional clustering was observed. Introns in the nad1, nad4, and nad7 genes were larger than those reported in other plants, indicating that increased intron sizes have contributed to mitochondrial genome expansion in cucumber. Mitochondrial genes atp6 and atp9 are physically close to each other and co-transcribed. These physical contigs will be useful for eventual sequencing of the cucumber mitochondrial DNA, which can be exploited to more efficiently screen for unique rearrangements affecting mitochondrial gene expression.