Meiosis Drives Extraordinary Genome Plasticity in the Haploid Fungal Plant Pathogen Mycosphaerella graminicola
Open Access
- 10 June 2009
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLOS ONE
- Vol. 4 (6), e5863
- https://doi.org/10.1371/journal.pone.0005863
Abstract
Meiosis in the haploid plant-pathogenic fungus Mycosphaerella graminicola results in eight ascospores due to a mitotic division following the two meiotic divisions. The transient diploid phase allows for recombination among homologous chromosomes. However, some chromosomes of M. graminicola lack homologs and do not pair during meiosis. Because these chromosomes are not present universally in the genome of the organism they can be considered to be dispensable. To analyze the meiotic transmission of unequal chromosome numbers, two segregating populations were generated by crossing genetically unrelated parent isolates originating from Algeria and The Netherlands that had pathogenicity towards durum or bread wheat, respectively. Detailed genetic analyses of these progenies using high-density mapping (1793 DArT, 258 AFLP and 25 SSR markers) and graphical genotyping revealed that M. graminicola has up to eight dispensable chromosomes, the highest number reported in filamentous fungi. These chromosomes vary from 0.39 to 0.77 Mb in size, and represent up to 38% of the chromosomal complement. Chromosome numbers among progeny isolates varied widely, with some progeny missing up to three chromosomes, while other strains were disomic for one or more chromosomes. Between 15–20% of the progeny isolates lacked one or more chromosomes that were present in both parents. The two high-density maps showed no recombination of dispensable chromosomes and hence, their meiotic processing may require distributive disjunction, a phenomenon that is rarely observed in fungi. The maps also enabled the identification of individual twin isolates from a single ascus that shared the same missing or doubled chromosomes indicating that the chromosomal polymorphisms were mitotically stable and originated from nondisjunction during the second division and, less frequently, during the first division of fungal meiosis. High genome plasticity could be among the strategies enabling this versatile pathogen to quickly overcome adverse biotic and abiotic conditions in wheat fields.Keywords
This publication has 48 references indexed in Scilit:
- Genome instability: a mechanistic view of its causes and consequencesNature Reviews Genetics, 2008
- Dothideomycete–Plant Interactions Illuminated by Genome Sequencing and EST Analysis of the Wheat Pathogen Stagonospora nodorumPlant Cell, 2007
- Validation of the high-throughput marker technology DArT using the model plant Arabidopsis thalianaMolecular Genetics and Genomics, 2005
- The genome sequence of the rice blast fungus Magnaporthe griseaNature, 2005
- Chromosomal Translocation and Segmental Duplication in Cryptococcus neoformansEukaryotic Cell, 2005
- Effects of genotyping errors, missing values and segregation distortion in molecular marker data on the construction of linkage mapsHeredity, 2003
- Technical NoteMolecular Ecology, 1998
- Construction of integrated genetic linkage maps by means of a new computer package: JoinMapThe Plant Journal, 1993
- Observations on the Effects of a Chromosome Duplication in Aspergillus NidulansJournal of General Microbiology, 1966
- THE CYTOLOGY OF THE FUNGIAnnual Review of Microbiology, 1951