Meiotic Recombination in Neurospora crassa Proceeds by Two Pathways with Extensive Holliday Junction Migration

• Published in: PloS one Vol. 11; no. 1; p. e0147815
• Main Authors: Yeadon, Patricia Jane, Bowring, Frederick James, Catcheside, David E A
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.01.2016; Public Library of Science (PLoS)
• Subjects: Alleles; Biology and Life Sciences; Chromosomes; Disjunction; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; DNA, Cruciform - genetics; DNA, Cruciform - metabolism; Fluorescence; Fluorescent indicators; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Genetic aspects; Genetic recombination; Homologous Recombination; Meiosis; Migration; Mutation; Neurospora; Neurospora crassa; Neurospora crassa - genetics; Phenotype; Physiological aspects; Recombination; Research and Analysis Methods; Restoration; Saccharomyces cerevisiae; Spores; Yeast; Australia; South Australia Australia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0147815

Analysis of thousands of Δmsh-2 octads using our fluorescent recombination system indicates that, as in other filamentous fungi, symmetric heteroduplex is common in the his-3 region of Neurospora crassa. Symmetric heteroduplex arises from Holliday junction migration, and we suggest this mechanism explains the high frequency of His+ spores in heteroallelic crosses in which recombination is initiated cis to the his-3 allele further from the initiator, cog+. In contrast, when recombination is initiated cis to the his-3 allele closer to cog+, His+ spores are mainly a result of synthesis-dependent strand annealing, yielding asymmetric heteroduplex. Loss of Msh-2 function increases measures of allelic recombination in both his-3 and the fluorescent marker gene, indicating that mismatches in asymmetric heteroduplex, as in Saccharomyces cerevisiae, tend to be repaired in the direction of restoration. Furthermore, the presence of substantial numbers of conversion octads in crosses lacking Msh-2 function suggests that the disjunction pathway described in S. cerevisiae is also active in Neurospora, adding to evidence for a universal model for meiotic recombination.