A Novel Gene, Le-Dd 10, Is Involved in Fruiting Body Formation of Lentinula Edodes

The cDNA library prepared from Lentinula edodes, Hokken 600 (H600), primordia was screened by using cDNA expressed specifically in Dictyostelium discoideum prestalk as a probe. Twenty-one clones, Le-Dd 1~21, were isolated from the L. edodes primordia cDNA library. Functional analysis of each gene was carried out by transformation into protoplast cells from L. edodes Mori 252 (M252) mycelia with the overexpression vector pLG-RasF1 of each gene because M252 protoplast cells were transformed with 11-fold higher efficiency than H600 cells. Transformants with the overexpression vector of Le-Dd10 formed a fruiting body at almost the same time as H600, a positive control, although M252, a negative control, did not form a fruiting body under culture conditions. This suggested that Le-Dd10 is involved in the formation of fruiting bodies. Single-strand conformation polymorphism analysis revealed that Le-Dd10 is located on No. 4 linkage group of L. edodes. The properties of Le-Dd10 products were investigated by Western blotting analysis using polyclonal antibodies against GST:Le-Dd10 fusion proteins. As a result, 56-kDa, 27-kDa, and 14-kDa protein bands appeared in primordial and fruiting body stages, although the expected molecular weight of the Le-Dd10 product was 50 kDa.

Cultivation of Edible Tropical Bolete, Phlebopus spongiosus, in Thailand and Yield Improvement by High-Voltage Pulsed Stimulation

Tropical bolete, Phlebopus spongiosus, is an edible ectomycorrhizal mushroom indigenous to northern Thailand. This mushroom has the ability to produce fruiting bodies without the need for a host plant. In this study, the technological cultivation of P. spongiosus was developed. Cultivation experiments indicated that fungal mycelia could completely colonize the cultivation substrate over a period of 85–90 days following inoculation of liquid inoculum. Primordia were induced under lower temperatures, high humidity and a 12-h photoperiod. Mature fruiting bodies were developed from young fruiting bodies within a period of one week. Consequently, yield improvement of P. spongiosus cultivation was determined by high-voltage pulsed stimulation. The results indicated that the highest degree of primordial formation, number of mature fruiting bodies and total weight values were obtained in cultivation experiments involving a high voltage of 40 kV. The total weight of the mushrooms increased by 1.4 times after applying high-voltage pulses when compared with the control. Additionally, the results revealed that the size of the fruiting body and the proximate composition of the fruiting bodies from high-voltage stimulation treatments were not different from the control. This research provides valuable information concerning successful cultivation techniques and yield improvement by high-voltage pulsed stimulation for the large-scale commercial fruiting body production of P. spongiosus.

Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes

Fruiting bodies of mushroom-forming fungi (Agaricomycetes) are among the most complex structures produced by fungi. Unlike vegetative hyphae, fruiting bodies grow determinately and follow a genetically encoded developmental program that orchestrates tissue differentiation, growth and sexual sporulation. In spite of more than a century of research, our understanding of the molecular details of fruiting body morphogenesis is limited and a general synthesis on the genetics of this complex process is lacking. In this paper, we aim to comprehensively identify conserved genes related to fruiting body morphogenesis and distill novel functional hypotheses for functionally poorly characterized genes. As a result of this analysis, we report 921 conserved developmentally expressed gene families, only a few dozens of which have previously been reported in fruiting body development. Based on literature data, conserved expression patterns and functional annotations, we provide informed hypotheses on the potential role of these gene families in fruiting body development, yielding the most complete description of molecular processes in fruiting body morphogenesis to date. We discuss genes related to the initiation of fruiting, differentiation, growth, cell surface and cell wall, defense, transcriptional regulation as well as signal transduction. Based on these data we derive a general model of fruiting body development, which includes an early, proliferative phase that is mostly concerned with laying out the mushroom body plan (via cell division and differentiation), and a second phase of growth via cell expansion as well as meiotic events and sporulation. Altogether, our discussions cover 1480 genes of Coprinopsis cinerea, and their orthologs in Agaricus bisporus, Cyclocybe aegerita, Armillaria ostoyae, Auriculariopsis ampla, Laccaria bicolor, Lentinula edodes, Lentinus tigrinus, Mycena kentingensis, Phanerochaete chrysosporium, Pleurotus ostreatus, and Schizophyllum commune, providing functional hypotheses for ~10% of genes in the genomes of these species. Although experimental evidence for the role of these genes will need to be established in the future, our data provide a roadmap for guiding functional analyses of fruiting related genes in the Agaricomycetes. We anticipate that the gene compendium presented here, combined with developments in functional genomics approaches will contribute to uncovering the genetic bases of one of the most spectacular multicellular developmental processes in fungi. Key words: functional annotation; comparative genomics; cell wall remodeling; development; fruiting body morphogenesis; mushroom; transcriptome

First report of Sarocladium kiliense causing brown rot of Hypsizygus marmoreus in China

Hyjpsizygus marmoreus (Peck) H.E. Bigelow is one of the most popular and widely cultivated edible mushrooms worldwide. In June 2021, an epidemic of H. marmoreus fruiting bodies infected with brown rot occurred at a cultivation facility in Yan’an (Shaanxi province), China, which resulted in a 90% economic loss. The fruiting body surface was covered with white-to-gray velvet-like mycelia, which gradually spread to the pileus, eventually covering the whole fruiting body (Fig. 1A). Brown rot, which is the most important factor limiting H. marmoreus fruiting body yield and quality, is responsible for severe economic losses in northern Shaanxi province. To identify the causal agent of this disease, small pieces of diseased tissue were collected from fruiting bodies, disinfected with 70% ethanol, and rinsed three times with sterile distilled water. They were then placed on potato dextrose agar (PDA) medium in plates and incubated at 26 °C. The colonies on the PDA medium after a 14-day incubation at 26 °C were 40–45 mm in diameter, orange–white on the surface (Fig. 1B), pale orange on the underside (Fig. 1C), slightly wrinkled or cerebriform, and glabrous or fasciculate. Vegetative hyphae were septate, hyaline, smooth, and thin-walled. The unicellular conidia were cylindrical with rounded ends (3.5 to 4.0 × 1.0 to 1.5 μm; n = 30). The cultural and morphological characteristics of the representative isolate MG1 were consistent with those of Sarocladium kiliense (Grütz) Summerbell (Giraldo et al. 2015). For the molecular identification, DNA was extracted from MG1. The internal transcribed spacer (ITS) region, a gene encoding the second largest RNA polymerase II subunit (RPB2), a β-tubulin gene (TUB2), and an actin gene (ACT) were amplified by PCR using primers ITS1/ITS4, fRPB2-5F/fRPB2-7cR, Bt2a/Bt2b, and ACT-512F/ACT-783R, respectively. The resulting ITS (MZ818340), RPB2 (MZ833454), TUB2 (MZ833455), and ACT (MZ833456) sequences from MG1 were 99.82%, 99.19%, 99.69%, and 99.22% identical to the corresponding sequences in S. kiliense isolate CBS 400.52 (ITS: KM231849, RPB2: KM232425, TUB2: KC479789, and ACT1: KM231258). On the basis of the morphological and molecular features, MG1 was identified as S. kiliense (Summerbell et al. 2011; Lombard et al. 2015; Giraldo et al. 2015). Pathogenicity tests, which were repeated three times, were conducted using conidial suspensions (approximately 1 × 105 spores/mL) prepared in sterile distilled water. The surface of 30 healthy H. marmoreus fruiting bodies maintained in a plastic box was sprayed with the MG1 conidial suspensions. Control H. marmoreus fruiting bodies were sprayed with sterile distilled water. The inoculated fruiting bodies were maintained in darkness at 25 °C and 95% relative humidity. The disease symptoms that developed in 3 days included the presence of gray mycelia on the fruiting body surface. Additionally, S. kiliense was reisolated from symptomatic pilei at 6 days post-inoculation. Disease symptoms were undetectable on the negative control. To the best of our knowledge, this is the first report of H. marmoreus infected with brown rot caused by S. kiliense in China.