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Open Access Research article

Comparative sequence analysis of Solanum and Arabidopsis in a hot spot for pathogen resistance on potato chromosome V reveals a patchwork of conserved and rapidly evolving genome segments

Agim Ballvora1*, Anika Jöcker1, Prisca Viehöver12, Hirofumi Ishihara23, Jürgen Paal1, Khalid Meksem3, Rémy Bruggmann4, Heiko Schoof1, Bernd Weisshaar12 and Christiane Gebhardt1

Author Affiliations

1 Max-Planck Institut für Züchtungsforschung, Carl von Linné Weg 10, 50829 Köln, Germany

2 Institut für Genomforschung, Universität Bielefeld, Universitätsstrasse 25, 33615 Bielefeld, Germany

3 Southern Illinois University at Carbondale, Dept. of Plant, Soil and General Agriculture, Carbondale, IL62901-4415, USA

4 GSF Forschungszentrum für Umwelt und Gesundheit, Institut für Bioinformatik, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany

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BMC Genomics 2007, 8:112  doi:10.1186/1471-2164-8-112

Published: 2 May 2007

Abstract

Background

Quantitative phenotypic variation of agronomic characters in crop plants is controlled by environmental and genetic factors (quantitative trait loci = QTL). To understand the molecular basis of such QTL, the identification of the underlying genes is of primary interest and DNA sequence analysis of the genomic regions harboring QTL is a prerequisite for that. QTL mapping in potato (Solanum tuberosum) has identified a region on chromosome V tagged by DNA markers GP21 and GP179, which contains a number of important QTL, among others QTL for resistance to late blight caused by the oomycete Phytophthora infestans and to root cyst nematodes.

Results

To obtain genomic sequence for the targeted region on chromosome V, two local BAC (bacterial artificial chromosome) contigs were constructed and sequenced, which corresponded to parts of the homologous chromosomes of the diploid, heterozygous genotype P6/210. Two contiguous sequences of 417,445 and 202,781 base pairs were assembled and annotated. Gene-by-gene co-linearity was disrupted by non-allelic insertions of retrotransposon elements, stretches of diverged intergenic sequences, differences in gene content and gene order. The latter was caused by inversion of a 70 kbp genomic fragment. These features were also found in comparison to orthologous sequence contigs from three homeologous chromosomes of Solanum demissum, a wild tuber bearing species. Functional annotation of the sequence identified 48 putative open reading frames (ORF) in one contig and 22 in the other, with an average of one ORF every 9 kbp. Ten ORFs were classified as resistance-gene-like, 11 as F-box-containing genes, 13 as transposable elements and three as transcription factors. Comparing potato to Arabidopsis thaliana annotated proteins revealed five micro-syntenic blocks of three to seven ORFs with A. thaliana chromosomes 1, 3 and 5.

Conclusion

Comparative sequence analysis revealed highly conserved collinear regions that flank regions showing high variability and tandem duplicated genes. Sequence annotation revealed that the majority of the ORFs were members of multiple gene families. Comparing potato to Arabidopsis thaliana annotated proteins suggested fragmented structural conservation between these distantly related plant species.