A single meiotic product dominates inheritance in Mucor circinelloides

Abstract

Meiosis is a major source of genetic diversity, yet it remains poorly understood in many pathogenic fungi. In Mucorales, the causative agents of mucormycosis, sexual reproduction has been difficult to study, and reported inheritance patterns have appeared inconsistent with conventional meiosis. Here, meiosis in Mucor circinelloides was demonstrated at genome-wide resolution by generating telomere-to-telomere chromosome assemblies from compatible mating types and analyzing parental markers distributed across the genome. The results reveal meiotic recombination and independent chromosome assortment. However, the outcome of meiosis is strikingly unconventional: all sexual spores derived from a single zygospore share an identical nuclear genotype, even when germination produces distinct sporangia. This pattern suggests that the viable progeny of each zygospore is derived from a single meiotic product, rather than from the four products expected under conventional meiosis. Mitochondrial inheritance is also uniparental, with progeny mitochondria inherited from the (+) mating-type parent. Together, these findings show that sexual reproduction in M. circinelloides entails meiotic recombination, but restricts inheritance to a single viable nuclear product and a single mitochondrial lineage. This decoupling of recombination from equal meiotic contribution reveals a hidden layer of inheritance control in Mucorales, showing how pathogenic fungi can reshuffle chromosomes while producing genetically uniform sibling progeny, an outcome reminiscent of female meiosis in animals.