title: The pgip family in soybean and three other legume species: evidence for a birth-and-death model of evolution.
abstract: BACKGROUND
  Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) plant cell wall glycoproteins involved in plant immunity. They are typically encoded by gene families with a small number of gene copies whose evolutionary origin has been poorly investigated. Here we report the complete characterization of the full complement of the pgip family in soybean (Glycine max [L.] Merr.) and the characterization of the genomic region surrounding the pgip family in four legume species.
  
  
  RESULTS
  BAC clone and genome sequence analyses showed that the soybean genome contains two pgip loci. Each locus is composed of three clustered genes that are induced following infection with the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary, and remnant sequences of pgip genes. The analyzed homeologous soybean genomic regions (about 126 Kb) that include the pgip loci are strongly conserved and this conservation extends also to the genomes of the legume species Phaseolus vulgaris L., Medicago truncatula Gaertn. and Cicer arietinum L., each containing a single pgip locus. Maximum likelihood-based gene trees suggest that the genes within the pgip clusters have independently undergone tandem duplication in each species.
  
  
  CONCLUSIONS
  The paleopolyploid soybean genome contains two pgip loci comprised in large and highly conserved duplicated regions, which are also conserved in bean, M. truncatula and C. arietinum. The genomic features of these legume pgip families suggest that the forces driving the evolution of pgip genes follow the birth-and-death model, similar to that proposed for the evolution of resistance (R) genes of NBS-LRR-type.
authors.forename: Raviraj M
authors.initials: RM
authors.lastname: Kalunke
authors.forename: Alberto
authors.initials: A
authors.lastname: Cenci
authors.forename: Chiara
authors.initials: C
authors.lastname: Volpi
authors.forename: Donal M
authors.initials: DM
authors.lastname: O'Sullivan
authors.forename: Luca
authors.initials: L
authors.lastname: Sella
authors.forename: Francesco
authors.initials: F
authors.lastname: Favaron
authors.forename: Felice
authors.initials: F
authors.lastname: Cervone
authors.forename: Giulia
authors.initials: G
authors.lastname: De Lorenzo
authors.forename: Renato
authors.initials: R
authors.lastname: D'Ovidio
mesh_terms: D005075:Biological Evolution; D007887:Fabaceae / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000235:genetics / Q000378:metabolism*
chemical_list: C081479:PGIP protein, plant; D010940:Plant Proteins