Chromosome-Wide Characterization of Intragenic Crossover in Shiitake Mushroom, Lentinula edodes

Meiotic crossover plays a critical role in generating genetic variations and is a central component of breeding. However, our understanding of crossover in mushroom-forming fungi is limited. Here, in Lentinula edodes, we characterized the chromosome-wide intragenic crossovers, by utilizing the single-nucleotide polymorphisms (SNPs) datasets of an F₁ haploid progeny. A total of 884 intragenic crossovers were identified in 110 single-spore isolates, the majority of which were closer to transcript start sites. About 71.5% of the intragenic crossovers were clustered into 65 crossover hotspots. A 10 bp motif (GCTCTCGAAA) was significantly enriched in the hotspot regions. Crossover frequencies around mating-type A (MAT-A) loci were enhanced and formed a hotspot in L. edodes. Genome-wide quantitative trait loci (QTLs) mapping identified sixteen crossover-QTLs, contributing 8.5-29.1% of variations. Most of the detected crossover-QTLs were co-located with crossover hotspots. Both cis- and trans-QTLs contributed to the nonuniformity of crossover along chromosomes. On chr2, we identified a QTL hotspot that regulated local, global crossover variation and crossover hotspot in L. edodes. These findings and observations provide a comprehensive view of the crossover landscape in L. edodes, and advance our understandings of conservation and diversity of meiotic recombination in mushroom-forming fungi.