Life cycle transcriptomics of the homothallic cultivated morel (Morchella rufobrunnea)

Morels (Morchella spp.) are iconic edible spring mushrooms renowned for their unique, meaty and earthy flavor profile. Wild-foraged morels are heavily relied upon to meet consumer demands, but optimizing cultivation is becoming critical as popularity continues to grow. The mating systems of Morchella spp. are of particular interest given their relevance to cultivation. Both heterothallic (outcrossing) and homothallic (self-fertile) life cycles have been reported. Here, we sequenced the genome of a commercial strain of Morchella rufobrunnea (GMI-8) to examine the genomic architecture surrounding the mating-type (MAT) loci and to provide a reference for transcriptomic analyses across its life cycle. To investigate gene regulation across developmental stages, we generated transcriptomes from six tissue types (sclerotia, mycelium, conidia, fundament, stipe, and hymenium) representing five key life stages. This sampling allowed us to profile the expression of mating-related, growth, and developmental associated genes across these life stages. Our analyses revealed a haploid genome size of 58 Mb, and co-localization of both MAT genes as required for sexual reproduction, confirming homothallism in this species. MAT genes (MAT1-1-1, 1-1-10, and 1-2-1) were highly expressed in conidial, fundament, and hymenial tissues, supporting the hypothesis that conidia may function as a nuclear donor/spermatia. This work improves our understanding of sexual reproduction and the life cycle of Morchella, and establishes a genomic and transcriptomic foundation for future studies of Morchella developmental biology.