Plant & Animal Genome IX Conference

Poster: Sequencing & EST
P01_67.html

SEQUENCING OF A 350-KILOBASE REGION OF MAIZE CHROMOSOME 4S ENCOMPASSING THE 22-KDA ALPHA-ZEIN GENE SUBFAMILY

The Plant Genome Initiative at Rutgers, Waksman Institute Rutgers, The State University of New Jersey Piscataway, NJ 08854-8020. http://pgir.rutgers.edu

Analysis of the 22-kDa a-zein multigene family helps elucidating mechanisms involved in genome expansion and gene regulation in grasses. To determine the physical arrangement of the members of this gene family, a bacterial artificial chromosome (BAC) library was constructed from maize inbred BSSS53. Two overlapping BAC clones resulted in a 348-kb contiguous sequence containing 22 members of the 22-kDa a-zein gene family. All genes were tandemly arrayed within 200 kb, with the 5' member located 50 kb from the genetically linked marker php20725. Clones containing one additional 22-kDa a-zein gene, azs22;16, were not physically linked to this cluster. Genetic mapping placed this gene at the floury-2 locus, approximately 20 cM proximal to php20725. The zein gene azs22;16 appears to be the wild type allele of floury-2 because their encoded proteins differ at an amino acid that affects processing of the signal peptide. To study the evolution of the 22-kDa a zein gene family, the coding sequences for all members of the family were compared and a phylogenetic tree was constructed. Parsimony analysis suggests that azs22;13 is the oldest member of the family, predating the separation of sorghum and maize 16.5 million years ago. The significance of paralogous and orthologous sequence analysis in determining the evolution of clustered gene families will be discussed.