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Evolution of the Group 1 late embryogenesis abundant (Lea) genes: analysis of the Lea B19 gene family in barley
Authors:Robin A P Stacy  Mari Espelund  Stein Sæbøe-Larssen  Kristin Hollung  Even Helliesen  Kjetill S Jakobsen
Institution:(1) Division of General Genetics, University of Oslo, Blindern, P.O. Box 1031, N-0315 Oslo, Norway;(2) Division of Botany, University of Oslo, Blindern, P.O. Box 1045, N-0315 Oslo, Norway
Abstract:The highly conserved Group 1 late embryogenesis abundant (Lea) genes are present in the genome of most plants as a gene family. Family members are conserved along the entire coding region, especially within the extremely hydrophilic internal 20 amino acid motif, which may be repeated. Cloning of Lea Group 1 genes from barley resulted in the characterization of four family members named B19.1, B19.1b, B19.3 and B19.4 after the presence of this motif 1, 1, 3 and 4 times in each gene, respectively. We present here the results of comparative and evolutionary analyses of the barley Group 1 Lea gene family (B19). The most important findings resulting from this work are (1) the tandem clustering of B19.3 and B19.4, (2) the spatial conservation of putative regulatory elements between the four B19 gene promoters, (3) the determination of the relative lsquoagersquo of the gene family members and (4) the lsquochimericrsquo nature of B19.3 and B19.4, reflecting a cross-over or gene-conversion event in their common ancestor. We also show evidence for the presence of one or two additional expressed B19 genes in the barley genome. Based on our results, we present a model for the evolution of the family in barley, including the 20 amino acid motif. Comparisons of the relatedness between the barley family and all other known Group 1 Lea genes using maximum parsimony (PAUP) analysis provide evidence for the time of divergence between the barley genes containing the internal motif as a single copy and as a repeat. The PAUP analyses also provide evidence for independent duplications of Group 1 genes containing the internal motif as a repeat in both monocots and dicots.
Keywords:ABA-inducible genes  coding region repeats  embryo-specific gene family  evolution  Hordeum vulgare L    phylogenetic analysis
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