hide
Free keywords:
-
Abstract:
Meiotic recombination is unevenly distributed throughout the genome. As a consequence, genetic and physical map distances do not have a simple linear relationship. Recombination hot spots and cold spots have been described in many fungi and recombination rates may in part reflect global features of chromosome structure. Here, we report that recombination is elevated adjacent to the mating type locus (MAT) in the pathogenic basidiomycete Cryptococcus neoformans. C. neoformans has an unusually large MAT locus, and recombination is suppressed between the alleles of this sexually dimorphic region of the genome. By introducing genetic markers at defined physical distances on both sides of MAT, we scored the meiotic recombination frequency on the MAT chromosome. The frequency of meiotic recombination is ~20% between the MAT locus and a flanking marker at 5, 10, 50 or 100 kb from the right or left border of MAT. This is approximately ten times higher than the recombination frequency between the markers at 10 and 100 kb from the MAT right border. Moreover, we found that recombination frequently occurs on both the left and the right sides of MAT. This result suggests that during meiosis, C. neoformans may exchange the MAT locus onto different genetic backgrounds and meanwhile, restrict the MAT locus from expanding to prevent capture of the entire chromosome. MAT linked recombinational enhancers may also have facilitated capture of genes into MAT by enabling rapid assimilation into both mating type alleles. W e are currently investigating whether recombinational enhancers flank MAT or reside in the a or alpha MAT allele, and testing if MAT heterozygosity is required to stimulate recombination.
