title: Comparative and evolutionary analysis of major peanut allergen gene families.
abstract: Peanut (Arachis hypogaea L.) causes one of the most serious food allergies. Peanut seed proteins, Arah1, Arah2, and Arah3, are considered to be among the most important peanut allergens. To gain insights into genome organization and evolution of allergen-encoding genes, approximately 617 kb from the genome of cultivated peanut and 215 kb from a wild relative were sequenced including three Arah1, one Arah2, eight Arah3, and two Arah6 gene family members. To assign polarity to differences between homoeologous regions in peanut, we used as outgroups the single orthologous regions in Medicago, Lotus, common bean, chickpea, and pigeonpea, which diverged from peanut about 50 Ma and have not undergone subsequent polyploidy. These regions were also compared with orthologs in many additional dicot plant species to help clarify the timing of evolutionary events. The lack of conservation of allergenic epitopes between species, and the fact that many different proteins can be allergenic, makes the identification of allergens across species by comparative studies difficult. The peanut allergen genes are interspersed with low-copy genes and transposable elements. Phylogenetic analyses revealed lineage-specific expansion and loss of low-copy genes between species and homoeologs. Arah1 syntenic regions are conserved in soybean, pigeonpea, tomato, grape, Lotus, and Arabidopsis, whereas Arah3 syntenic regions show genome rearrangements. We infer that tandem and segmental duplications led to the establishment of the Arah3 gene family. Our analysis indicates differences in conserved motifs in allergen proteins and in the promoter regions of the allergen-encoding genes. Phylogenetic analysis and genomic organization studies provide new insights into the evolution of the major peanut allergen-encoding genes.
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia Directorate of Soybean Research, Indian Council of Agriculture Research (ICAR), Indore, (M.P.), India.
authors.forename: Milind B
authors.initials: MB
authors.lastname: Ratnaparkhe
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Tae-Ho
authors.initials: TH
authors.lastname: Lee
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Xu
authors.initials: X
authors.lastname: Tan
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia Center for Genomics and Computational Biology, School of Life Sciences, School of Sciences, Hebei United University, Tangshan, Hebei, China.
authors.forename: Xiyin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Jingping
authors.initials: J
authors.lastname: Li
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Changsoo
authors.initials: C
authors.lastname: Kim
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Rainville
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lemke
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Rosana O
authors.initials: RO
authors.lastname: Compton
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia.
authors.forename: Jon
authors.initials: J
authors.lastname: Robertson
authors.affiliation: Department of Molecular Biosciences and Bioengineering, University of Hawaii at Mānoa.
authors.forename: Maria
authors.initials: M
authors.lastname: Gallo
authors.affiliation: University of Brasília, Campus Universitário Darcy Ribeiro, DF, Brazil.
authors.forename: David J
authors.initials: DJ
authors.lastname: Bertioli
authors.affiliation: Plant Genome Mapping Laboratory, University of Georgia paterson@plantbio.uga.edu.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Paterson
mesh_terms: D000485:Allergens / Q000235:genetics* / Q000276:immunology; D000595:Amino Acid Sequence; D010367:Arachis / Q000145:classification / Q000235:genetics* / Q000276:immunology; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000276:immunology; D010944:Plants / Q000145:classification / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment
chemical_list: D000485:Allergens; D010940:Plant Proteins
keywords: Arachis hypogaea L.; allergens; evolution; gene synteny; genome organization; homologs