Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

COMPARATIVE GENOMIC MAPPING BETWEEN A 4-CM REGION FLANKING DREB1A IN ARABIDOPSIS THALIANA AND MAIZE

VAN BUUREN M. L., SERHANI B.

Department of Agroenvironmental Science and Technology, University of Bologna

marianne@kaiser.alma.unibo.it

Arabidopsis thaliana, colinearity, comparative mapping, orthology, Zea mays

The comparative mapping between model plant species for which the complete genome sequence is known and crop species may provide a new strategy for the isolation of agronomically valuable genes.

In this study, we tested whether comparative mapping between Arabidopsis and maize of a small region (4 cM) surrounding the DREB1A gene in Arabidopsis could lead to the identification of an orthologous region in maize containing the DREB1A homolog. The genomic sequence information available for Arabidopsis allowed for the selection of conserved, single-copy genes that were used for the identification of maize homologs in a large EST database. In total, 18 maize homologs were mapped. A second BLAST comparison of these genes to the recently completed Arabidopsis sequence revealed that 15 homologs are likely to be orthologous as the highest similarity score was obtained either with the original Arabidopsis gene or with a highly similar Arabidopsis gene localized on a duplication of this region present on chromosome 5. These duplicated regions are a remainder of a large scale genomic duplication in Arabidopsis that occurred after the divergence of monocots and dicots. Therefore, highest sequence similarity of a maize gene to either of two duplicated genes in these regions can be considered as indicative of orthology.

The map position of these genes showed significant colinearity with the Arabidopsis contig. Five genes of these genes map to chromosome 10: three genes in bin 03 within 2.4 cM, one gene (9) in bin 04 at 4.5 cM from the closest gene in bin 03, and one gene in bin 07. Furthermore, the position of three genes is colinear with that found for the corresponding homologs in Arabidopsis. DREB1A and another gene were assigned to bins 01 and 02, respectively, on chromosome 6 in a 15 cM interval. These results indicate that comparative mapping of conserved genes present in single or low copy is a valid approach to generate cross-species reference maps. Nevertheless, frequent duplications and rearrangements in the Arabidopsis genome as well as the evolutionary distance between Arabidopsis and maize make it unlikely that orthology and colinearity between these two species are sufficient to aid gene prediction and cloning in maize.