Limitation of nitrogen source facilitated the production of nonmeiotic recombinants in Aspergillus nidulans

Abstract

Aspergillus nidulans is a fungal model organism extensively used in genetic approaches. It may reproduce sexually and asexually, with a well‐defined parasexual cycle. The current paper demonstrates that the limitation of nitrogen source facilitates the production of A. nidulans's nonmeiotic recombinants directly from heterokaryons, without the recovery of the diploid phase. Heterokaryons formed between master strains were inoculated in sodium nitrate‐low (basal medium [BM]) and sodium nitrate‐rich media (minimal medium [MM]). All mitotic segregants produced by the heterokaryons were tested for their mitotic stability in the presence of benomyl, the haploidizing agent. Only mitotically stable haploid segregants were selected for subsequent analysis. Phenotypic analyses of such haploids favored the characterization of nonmeiotic recombinants. As the number of such recombinants was higher in BM than in MM, nitrogen limitation may have facilitated the isolation of nonmeiotic recombinants from heterokaryons by stimulating nuclear fusion still inside the heterokaryotic mycelium as a survival strategy.

Population genomics reveals meiotic recombination in Fusarium oxysporum

“…Fayyaz et al observe that meiosis-related genes are present in F. oxysporum and that recombination is more frequent toward the telomeres, which suggests sexual recombination. However, the same may hold for a type of parasexual recombination called parameiosis, in which unstable diploid nuclei in heterokaryotic mycelium undergo mitotic recombination and haploidization ( 17 ). In Candida albicans , recombination during parameiosis depends on at least two meiosis-specific genes ( 18 ).…”