Strain degeneration has been defined as a decrease or loss in the yield of important commercial traits resulting from subsequent culture, which ultimately leads to Reactive Oxygen Species (ROS) production. Pleurotus ostreatus is a lignin-producing nematophagous edible mushroom. Mycelia for mushroom production are usually maintained in subsequent culture in solid media and frequently show symptoms of strain degeneration. The dikaryotic strain P. ostreatus (DkN001) has been used in our lab as a model organism for different purposes. Hence, different tools have been developed to uncover genetic and molecular aspects of this fungus. In this work, strain degeneration was studied in a full-sib monokaryotic progeny of the DkN001 strain with fast (F) and slow (S) growth rates by using different experimental approaches (light microscopy, malondialdehyde levels, whole-genome transcriptome analysis, and chitosan effect on monokaryotic mycelia). The results obtained showed that: (i) strain degeneration in P. ostreatus is linked to oxidative stress, (ii) the oxidative stress response in monokaryons is genotype dependent, (iii) stress and detoxifying genes are highly expressed in S monokaryons with symptoms of strain degeneration, (iv) chitosan addition to F and S monokaryons uncovered the constitutive expression of both oxidative stress and cellular detoxifying genes in S monokaryon strains which suggest their adaptation to oxidative stress, and (v) the overexpression of the cell wall genes, Uap1 and Cda1, in S monokaryons with strain degeneration phenotype indicates cell wall reshaping and the activation of High Osmolarity Glycerol (HOG) and Cell Wall Integrity (CWI) pathways. These results could constitute a hallmark for mushroom producers to distinguish strain degeneration in commercial mushrooms.

Truffles are ascomycete hypogeous fungi belonging to the Tuberaceae family of the Pezizales order that grow in ectomycorrhizal symbiosis with tree roots, and they are known for their peculiar aromas and flavors. The axenic culture of truffle mycelium is problematic because it is not possible in many cases, and the growth rate is meager when it is possible. This limitation has prompted searching and characterizing new strains that can be handled in laboratory conditions for basic and applied studies. In this work, a new strain of Tuber borchii (strain SP1) was isolated and cultured, and its transcriptome was analyzed under different in vitro culture conditions. The results showed that the highest growth of T. borchii SP1 was obtained using maltose-enriched cultures made with soft-agar and in static submerged cultures made at 22 °C. We analyzed the transcriptome of this strain cultured in different media to establish a framework for future comparative studies, paying particular attention to the central metabolic pathways, principal secondary metabolite gene clusters, and the genes involved in producing volatile aromatic compounds (VOCs). The results showed a transcription signal for around 80% of the annotated genes. In contrast, most of the transcription effort was concentrated on a limited number of genes (20% of genes account for 80% of the transcription), and the transcription profile of the central metabolism genes was similar in the different conditions analyzed. The gene expression profile suggests that T. borchii uses fermentative rather than respiratory metabolism in these cultures, even in aerobic conditions. Finally, there was a reduced expression of genes belonging to secondary metabolite clusters, whereas there was a significative transcription of those involved in producing volatile aromatic compounds.

The search for new compounds of plant origin with antimicrobial activity has been the goal of many research groups, due to the increase in the number of microorganisms resistant to antimicrobials. The objective of this study was to evaluate the antimicrobial and antioxidant activity of two plant species, Tabebuia aurea (“paratudo”) and Cordia glabrata (“louro branco”), present in the state of Mato Grosso. The plant material (leaves and flowers) was extracted by maceration in 70% ethanol (Et) and polar hexane (Hex) (non-polar solvent). The determination of the antimicrobial activity was carried out by broth microdilution technique, and the antioxidant potential determined by the DPPH free radical method. In the evaluation of the antibacterial activity, the ethanolic extract of C. glabrata leaves presented better antibacterial potential for Staphylococcus aureus, revealing a minimum inhibitory concentration (MIC) of 125 μg / mL. However, for strains of Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium, all extracts of C. glabrata showed MICs of 2000 μg / mL or higher. The ethanolic and hexanic extracts of T. aurea flowers and leaves did not show promising antibacterial potential for any of the tested strains. In the evaluation of antifungal activity against Candida albicans and Candida parapsilosis, the hexanic extract of C. glabrata leaves presented weak to moderate activity only for the C. albicans strain (MIC = 1000 μg / mL). The remaining extracts of C. glabrata and the extracts of T. aurea were not promising against the tested yeasts, showing inhibitory concentrations equal to or greater than 2000 μg / mL. In the determination of the antioxidant potential, the polar extracts (Et 70%) had a higher capacity to sequester the DPPH radical than the capacity obtained for the apolar extracts (Hex). The tests revealed promising antibacterial activity for Staphylococcus aureus and high antioxidant potential of the hydroethanolic extracts of leaves and flowers of C. glabrata, respectively.

Truffles are ascomycete hypogeous fungi belonging to the Tuberaceae family of the Pezizales order that grow in ectomycorrhizal symbiosis with tree roots and are known for their peculiar aromas and flavors. Axenic culture of truffle mycelium is problematic because it is not possible in many cases, and the growth rate is meager when it is possible. This limitation prompts searching and characterizing new strains that can be handled in laboratory conditions for basic and applied studies. In this work, a new strain of Tuber borchii (strain SP1) has been isolated and cultured, and its transcriptome has been analyzed under different in vitro culture conditions. The results show that the best T. borchii SP1 growth was obtained using maltose-enriched cultures made with soft-agar and in static submerged cultures made at 22ºC. The transcriptome analysis of this strain cultured in different media indicated that most of the gene transcription effort is due to a limited number of genes (20% of genes account for 80% of the transcription), that the transcription profile of the central metabolism genes was similar in the different conditions analyzed with a transcription signal detected for around 80% of the annotated genes. The gene expression profile suggests that T. borchii uses a fermentative rather than respiratory metabolism, even in aerobic conditions. Finally, there is a reduced expression of genes belonging to secondary metabolite clusters, whereas there is a significative transcription of those involved in producing volatile aromatic compounds.