Organization and Unconventional Integration of the Mating-Type Loci in Morchella Species

Structure of the Mating-Type Genes and Mating Systems of Verpa bohemica and Verpa conica (Ascomycota, Pezizomycotina)

Verpa spp. are potentially important economic fungi within Morchellaceae. However, fundamental research on their mating systems, the key aspects of their life cycle, remains scarce. Fungal sexual reproduction is chiefly governed by mating-type genes, where the configuration of these genes plays a pivotal role in facilitating the reproductive process. For this study, de novo assembly methodologies based on genomic data from Verpa spp. were employed to extract precise information on the mating-type genes, which were then precisely identified in silico and by amplifying their single-ascospore populations using MAT-specific primers. The results suggest that the MAT loci of the three tested strains of V. bohemica encompassed both the MAT1-1-1 and MAT1-2-1 genes, implying homothallism. On the other hand, amongst the three V. conica isolates, only the MAT1-1-1 or MAT1-2-1 genes were present in their MAT loci, suggesting that V. conica is heterothallic. Moreover, bioinformatic analysis reveals that the three tested V. bohemica strains and one V. conica No. 21110 strain include a MAT1-1-10 gene in their MAT loci, while the other two V. conica strains contained MAT1-1-11, exhibiting high amino acid identities with those from corresponding Morchella species. In addition, MEME analysis shows that a total of 17 conserved protein motifs are present among the MAT1-1-10 encoded protein, while the MAT1-1-11 protein contained 10. Finally, the mating type genes were successfully amplified in corresponding single-ascospore populations of V. bohemica and V. conica, further confirming their life-cycle type. This is the first report on the mating-type genes and mating systems of Verpa spp., and the presented results are expected to benefit further exploitation of these potentially important economic fungi.

Large-Scale Field Cultivation of Morchella and Relevance of Basic Knowledge for Its Steady Production

Morels are one of the most highly prized edible and medicinal mushrooms worldwide. Therefore, historically, there has been a large international interest in their cultivation. Numerous ecological, physiological, genetic, taxonomic, and mycochemical studies have been previously developed. At the beginning of this century, China finally achieved artificial cultivation and started a high-scale commercial development in 2012. Due to its international interest, its cultivation scale and area expanded rapidly in this country. However, along with the massive industrial scale, a number of challenges, including the maintenance of steady economic profits, arise. In order to contribute to the solution of these challenges, formal research studying selection, species recognition, strain aging, mating type structure, life cycle, nutrient metabolism, growth and development, and multi-omics has recently been boosted. This paper focuses on discussing current morel cultivation technologies, the industrial status of cultivation in China, and the relevance of basic biological research, including, e.g., the study of strain characteristics, species breeding, mating type structure, and microbial interactions. The main challenges related to the morel cultivation industry on a large scale are also analyzed. It is expected that this review will promote a steady global development of the morel industry based on permanent and robust basic scientific knowledge.

Importance of appropriate genome information for the design of mating type primers in black and yellow morel populations

Morels are highly prized edible fungi where sexual reproduction is essential for fruiting-body production. As a result, a comprehensive understanding of their sexual reproduction is of great interest. Central to this is the identification of the reproductive strategies used by morels. Sexual reproduction in fungi is controlled by mating-type (MAT) genes and morels are thought to be mainly heterothallic with two idiomorphs, MAT1-1 and MAT1-2. Genomic sequencing of black (Elata clade) and yellow (Esculenta clade) morel species has led to the development of PCR primers designed to amplify genes from the two idiomorphs for rapid genotyping of isolates from these two clades. To evaluate the design and theoretical performance of these primers we performed a thorough bioinformatic investigation, including the detection of the MAT region in publicly available Morchella genomes and in-silico PCR analyses. All examined genomes, including those used for primer design, appeared to be heterothallic. This indicates an inherent fault in the original primer design which utilized a single Morchella genome, as the use of two genomes with complementary mating types would be required to design accurate primers for both idiomorphs. Furthermore, potential off-targets were identified for some of the previously published primer sets, but verification was challenging due to lack of adequate genomic information and detailed methodologies for primer design. Examinations of the black morel specific primer pairs (MAT11L/R and MAT22L/R) indicated the MAT22 primers would correctly target and amplify the MAT1-2 idiomorph, but the MAT11 primers appear to be capable of amplifying incorrect off-targets within the genome. The yellow morel primer pairs (EMAT1-1 L/R and EMAT1-2 L/R) appear to have reporting errors, as the published primer sequences are dissimilar with reported amplicon sequences and the EMAT1-2 primers appear to amplify the RNA polymerase II subunit (RPB2) gene. The lack of the reference genome used in primer design and descriptive methodology made it challenging to fully assess the apparent issues with the primers for this clade. In conclusion, additional work is still required for the generation of reliable primers to investigate mating types in morels and to assess their performance on different clades and across multiple geographical regions.