An MSH4 Homolog, stpp1 , from Pleurotus pulmonarius Is a “Silver Bullet” for Resolving Problems Caused by Spores in Cultivated Mushrooms

Abstract

The enormous number of spores produced by fruiting bodies during cultivation of mushrooms can lead to allergic reactions of workers, reduction of commercial value, spread of mushroom disease, pollution of facilities, and depletion of genetic diversity in natural populations. A cultivar harboring a sporulation-deficient (sporeless) mutation would be very useful for preventing these problems, but sporeless commercial cultivars are very limited in usefulness because sporeless traits are often linked with traits that are unfavorable for commercial cultivation. Thus, identifying a causal gene of a sporeless phenotype not linked to the adverse traits in breeding and cultivation is crucial for the establishment of sporeless breeding using a strategy employing targeting induced local lesions in genomes (TILLING) in cultivated mushrooms. We used a Pleurotus pulmonarius (Fr.) Quél. sporeless strain to identify and characterize the single recessive gene controlling the mutation. The 3,853-bp stpp1 gene encodes a protein of 854 amino acids and belongs to the MutS homolog (MSH) family associated with mismatch repair in DNA synthesis or recombination in meiosis. Gene expression analysis of the fruiting body showed that this gene is strongly expressed in the gills. Phenotypic analysis of disruptants formed by gene targeting suggested a reproducible sporeless phenotype. Mutants deficient in a functional copy of this gene have no unfavorable traits for sporeless cultivar breeding, so this gene will be an extremely useful target for efficient and versatile sporeless breeding in P. pulmonarius and various other cultivated mushrooms.

Comparative Analysis of Sporulating and Spore-Deficient Strains of Agrocybe salicacola Based on the Transcriptome Sequences

“…In the current study, transcriptome analyses revealed that a large number of genes related to metabolic, cellular, and other biological processes might be involved in spore development were up-or down-regulated in the test strains. The majority of these genes encoded enzymes involved in DNA repair or homologous recombination were down-regulated in the mutant strains; these finding differ from those of previous reports [25]. Additional studies identified the gene fragments CL11 and 11355 as homologs of the DNA repair gene rad 8 in C. cinerea, and these fragments were not expressed in the mycelia or fruiting bodies of the three mutant strains.…”

“…Although some genetic sites were identified as potentially related to the regulation of spore development, few genes were discovered in these sequences [15,16,25], and only the single gene stpp1, which is an MSH4 homolog in P. pulmonarius, had a verified function after genetic transformation [25]. Therefore, the identification of additional genes that are related to spore generation will provide important evidence for studying the sexual development and breeding of edible fungi.…”

“…According to previous reports [15,16,25], some differentially expressed genes that potentially participate in homologous recombination, mismatch repair, nucleotide excision repair, base excision repair, and DNA replication were examined as the potential candidate targets. In addition, some gene fragments with obvious differential expression between the wild and mutant strains were also verified.…”

“…In the model species P. ostreatus, rad51, and dmc1 were isolated and recognized as the genes that play roles in spore formation based on their expression patterns [15,16]. However, only one gene, stpp1, which is an MSH4 homolog clone based on the AFLP marker [23,24] from P. pulmonarius, has been assessed using gene knockout [25].…”

How do Agaricomycetes shape their fruiting bodies? 1. Morphological aspects of development

“…Omissions of one or the other subroutine or chances within a subroutine will not inevitably fully break down the whole process of fruiting whose ultimate biological target is genetic recombination and the production of meiotic basidiospores. Noteworthy for commercial mushroom cultivation, a block in basidiospore production for example can still give perfectly shaped mushrooms and these can overcome the problems of spore-induced allergies for mushroom growers and consumers (Hasebe et al, 1991;K€ ues et al, 2007;Okuda et al, 2013).…”