title: Genome structure impacts molecular evolution at the AvrLm1 avirulence locus of the plant pathogen Leptosphaeria maculans.
abstract: Leptosphaeria maculans, a dothideomycete fungus causing stem canker on oilseed rape, develops gene-for-gene interactions with its host plants. It has the ability to rapidly adapt to selection pressure exerted by cultivars harbouring novel resistance genes as exemplified recently by the 3-year evolution towards virulence at the AvrLm1 locus in French populations. The AvrLm1 avirulence gene was recently cloned and shown to be a solo gene within a 269 kb non-coding, heterochromatin-like region. Here we describe the sequencing of the AvrLm1 genomic region in one avirulent and two virulent isolates to investigate the molecular basis of evolution towards virulence at the AvrLm1 locus. For these virulent isolates, the gain of virulence was linked to a 260 kb deletion of a chromosomal segment spanning AvrLm1 and deletion breakpoints were identical or similar. Among the 460 isolates analysed from France, Australia and Mexico, a similar large deletion was apparent in > 90% of the virulent isolates. Deletion breakpoints were also strongly conserved in most of the virulent isolates, which led to the hypothesis that a unique deletion event leading to the avrLm1 virulence has diffused in pathogen populations. These data finally suggest that retrotransposons are key drivers in genome evolution and adaptation to novel selection pressure in L. maculans.
authors.affiliation: INRA, UMR1290 BIOGER-CPP, F-78026 Versailles, France. gout@versailles.inra.fr
authors.forename: Lilian
authors.initials: L
authors.lastname: Gout
authors.forename: Marie Line
authors.initials: ML
authors.lastname: Kuhn
authors.forename: Lucie
authors.initials: L
authors.lastname: Vincenot
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bernard-Samain
authors.forename: Laurence
authors.initials: L
authors.lastname: Cattolico
authors.forename: Martin
authors.initials: M
authors.lastname: Barbetti
authors.forename: Onésimo
authors.initials: O
authors.lastname: Moreno-Rico
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Balesdent
authors.forename: Thierry
authors.initials: T
authors.lastname: Rouxel
mesh_terms: D001203:Ascomycota / Q000235:genetics / Q000472:pathogenicity*; D001483:Base Sequence; D029688:Brassica napus / Q000382:microbiology*; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D005828:Genetics, Population; D016681:Genome, Fungal / Q000235:genetics*; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D014774:Virulence / Q000235:genetics
chemical_list: D005656:Fungal Proteins