It is becoming clear that simple sequence repeats (SSRs) play a significant role in fungal genome organization, and they are a large source of genetic markers for population genetics and meiotic maps. We identified SSRs in the Laccaria bicolor genome by in silico survey and analyzed their distribution in the different genomic regions. We also compared the abundance and distribution of SSRs in L. bicolor with those of the following fungal genomes: Phanerochaete chrysosporium,Coprinopsis cinerea, Ustilago maydis, Cryptococcus neoformans, Aspergillus nidulans, Magnaporthe grisea, Neurospora crassa and Saccharomyces cerevisiae. Using the MISA computer program, we detected 277,062 SSRs in the L. bicolor genome representing 8% of the assembled genomic sequence. Among the analyzed basidiomycetes, L. bicolor exhibited the highest SSR density although no correlation between relative abundance and the genome sizes was observed. In most genomes the short motifs (mono- to trinucleotides) were more abundant than the longer repeated SSRs. Generally, in each organism, the occurrence, relative abundance, and relative density of SSRs decreased as the repeat unit increased. Furthermore, each organism had its own common and longest SSRs. In the L. bicolor genome, most of the SSRs were located in intergenic regions (73.3%) and the highest SSR density was observed in transposable elements (TEs; 6,706 SSRs/Mb). However, 81% of the protein-coding genes contained SSRs in their exons, suggesting that SSR polymorphism may alter gene phenotypes. Within a L. bicolor offspring, sequence polymorphism of 78 SSRs was mainly detected in non-TE intergenic regions. Unlike previously developed microsatellite markers, these new ones are spread throughout the genome; these markers could have immediate applications in population genetics.
SSR density on the larger linkage groups (pseudochromosomes v.2.0) of L. bicolor containing the main part of the SSRs. The density is graphically represented as the SSRs found in a window of 10 kb
Percentage and density of genes, transposable elements and SSRs found on the linkage group 1 (LG1 v.2.0) of L. bicolor. a Percentage of genes (blue), TEs (red) and SSRs (yellow). 1 Relative percentage of genes, TEs and SSRs. 2 Relative percentage of genes and SSRs. 3 Relative percentage of TEs and SSRs. b The density is graphically represented as the number of genes, TEs and SSRs found in a window of 10 kb
Labbé J, Murat C, Morin E, Le Tacon F, Martin F. Survey and analysis of simple
sequence repeats in the Laccaria bicolor genome, with development of
microsatellite markers. Curr Genet. 2011 Apr;57(2):75-88. doi:
10.1007/s00294-010-0328-9. Epub 2010 Dec 4. PubMed PMID: 21132299.