title: Evolution of the EKA family of powdery mildew avirulence-effector genes from the ORF 1 of a LINE retrotransposon.
abstract: BACKGROUND
  The Avrk1 and Avra10 avirulence (AVR) genes encode effectors that increase the pathogenicity of the fungus Blumeria graminis f.sp. hordei (Bgh), the powdery mildew pathogen, in susceptible barley plants. In resistant barley, MLK1 and MLA10 resistance proteins recognize the presence of AVRK1 and AVRA10, eliciting the hypersensitive response typical of gene for gene interactions. Avrk1 and Avra10 have more than 1350 homologues in Bgh genome, forming the EKA (Effectors homologous to Avr k 1 and Avr a 10) gene family.
  
  
  RESULTS
  We tested the hypothesis that the EKA family originated from degenerate copies of Class I LINE retrotransposons by analysing the EKA family in the genome of Bgh isolate DH14 with bioinformatic tools specially developed for the analysis of Transposable Elements (TE) in genomes. The Class I LINE retrotransposon copies homologous to Avrk1 and Avra10 represent 6.5 % of the Bgh annotated genome and, among them, we identified 293 AVR/effector candidate genes. We also experimentally identified peptides that indicated the translation of several predicted proteins from EKA family members, which had higher relative abundance in haustoria than in hyphae.
  
  
  CONCLUSIONS
  Our analyses indicate that Avrk1 and Avra10 have evolved from part of the ORF1 gene of Class I LINE retrotransposons. The co-option of Avra10 and Avrk1 as effectors from truncated copies of retrotransposons explains the huge number of homologues in Bgh genome that could act as dynamic reservoirs from which new effector genes may evolve. These data provide further evidence for recruitment of retrotransposons in the evolution of new biological functions.
authors.affiliation: INRA, UR1164 URGI Unité de Recherche Génomique-Info, Institut National de la Recherche Agronomique de Versailles-Grignon, Versailles, 78026, France. joelle.amselem@versailles.inra.fr.|INRA, UR1290 BIOGER, Biologie et gestion des risques en agriculture, Campus AgroParisTech, 78850, Thiverval-Grignon, France. joelle.amselem@versailles.inra.fr.
authors.forename: Joelle
authors.initials: J
authors.lastname: Amselem
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK. marielle.vigouroux@jic.ac.uk.
authors.forename: Marielle
authors.initials: M
authors.lastname: Vigouroux
authors.affiliation: Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland. simoneoberhaensli@gmail.com.
authors.forename: Simone
authors.initials: S
authors.lastname: Oberhaensli
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK. james.brown@jic.ac.uk.
authors.forename: James K M
authors.initials: JK
authors.lastname: Brown
authors.affiliation: School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK. Laurence.Bindschedler@rhul.ac.uk.
authors.forename: Laurence V
authors.initials: LV
authors.lastname: Bindschedler
authors.affiliation: Laboratory of Genetics, Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, TK 11855, Athens, Greece. skamnioti.pari@gmail.com.
authors.forename: Pari
authors.initials: P
authors.lastname: Skamnioti
authors.affiliation: Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland. wicker@botinst.uzh.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wicker
authors.affiliation: Department of Life Sciences, Imperial College London, London, UK. p.spanu@imperial.ac.uk.
authors.forename: Pietro D
authors.initials: PD
authors.lastname: Spanu
authors.affiliation: INRA, UR1164 URGI Unité de Recherche Génomique-Info, Institut National de la Recherche Agronomique de Versailles-Grignon, Versailles, 78026, France. hadi.quesneville@versailles.inra.fr.
authors.forename: Hadi
authors.initials: H
authors.lastname: Quesneville
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA) and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223, Madrid, Spain. soledad.sacristan@upm.es.
authors.forename: Soledad
authors.initials: S
authors.lastname: Sacristán
mesh_terms: D001203:Ascomycota / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D019295:Computational Biology; D016384:Consensus Sequence; D005656:Fungal Proteins / Q000235:genetics*; D016681:Genome, Fungal; D001467:Hordeum / Q000382:microbiology*; D020084:Long Interspersed Nucleotide Elements; D005810:Multigene Family; D016366:Open Reading Frames; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D040901:Proteomics
chemical_list: D005656:Fungal Proteins