Nuclear conditions of basidiospores and hyphal cells in the edible mushroom Oudemansiella aparlosarca

Abstract

Oudemansiella aparlosarca is an edible mushroom possessing medicinal and health benefits. Although there are studies on the cultivation of O. aparlosarca, only a few studies have focused on its genetics and life cycle. Therefore, the main objective of this study was to identify the nuclear conditions of basidiospores and homokaryotic and heterokaryotic hyphal cells and to determine the influence of different nuclear conditions on basidiospore diameter in O. aparlosarca. Two parental strains: strain-55 and strain-81 were used. Staining of basidiospores and hyphal cells in the apical region was performed. We observed the following nuclear conditions: non-nucleate, mononucleate, binucleate, and multinucleate. In both parental strains, binucleate spores were predominant, while the number of non-nucleate spores was the lowest. The diameter of non-nucleate spores was the smallest, being 11.52 µm and 12.15 µm in parental strain-81 and strain-55, respectively, while multinucleate spores had the largest diameter, being 14.78 µm in both parental strains. Both homokaryotic and heterokaryotic strains were identified in isolated single spores from parental strains. Binucleate cells were majorly present in heterokaryotic hyphal cells, and multinucleate cells were predominant in homokaryotic hyphal cells. We conclude that O. aparlosarca contains homokaryotic and heterokaryotic basidiospores, which indicates an amphithallic life cycle. The observed binucleate spores might be the result of post-meiotic mitosis.

Keywords: Oudemansiella aparlosarca; amphithallic life cycle; binucleate; multinucleate; post-meiotic mitosis; spore size.

FIGURE 1

Mature fruiting bodies of (a) Parental strain‐55 and (b) Parental strain‐81

FIGURE 2

Nuclear conditions of Oudemansiella aparlosarca basidiospores. (a) Basidiospores observed under a fluorescence microscope. Red circles indicate binucleate spores, which were high in number; (b) Non‐nucleate spore; (c) Mononucleate spore; (d) Binucleate spore; (e) Multinucleate spore. Bars: a = 20 μm; b–e = 10 μm

FIGURE 3

Different nuclear conditions of basidiospores of parental strains 55 and 81. Values are expressed as percentage means ± SD of five replicates, and 500 basidiospores were observed in each replicate. According to Duncan's multiple range test, means in the same‐colored bars followed by the same superscripted letter within the observed nuclear conditions in a parental strain are not significantly different at p < 0.05. Means in the different colored bars followed by the superscripted “*” symbol of the observed non‐nucleate condition between the parental strains are significantly different at p < 0.05, according to the paired‐sample t test. The error bars denote standard deviation

FIGURE 4

Nuclear conditions of heterokaryotic hyphal cells in the apical region of Oudemansiella aparlosarca strain‐55 and strain‐81, observed under a fluorescence microscope. Red arrow indicates the nucleus; yellow arrow indicates clamp connection; (a) Non‐nucleate heterokaryotic hyphal cell; (b) Mononucleate heterokaryotic hyphal cell; (c) Binucleate heterokaryotic hyphal cell; (d) Multinucleate heterokaryotic hyphal cell. Bar: 50 μm

FIGURE 5

Nuclear conditions of homokaryotic hyphal cells in the apical region of Oudemansiella aparlosarca strain‐55 and strain‐81, observed under a fluorescence microscope. Red arrow indicates the nucleus; yellow arrow indicates septa of hyphal cell; (a) Non‐nucleate homokaryotic hyphal cell; (b) Mononucleate homokaryotic hyphal cells; (c) Binucleate homokaryotic hyphal cell; (d) Multinucleate homokaryotic hyphal cell. Bar: 50 μm

FIGURE 6

Different nuclear conditions of Oudemansiella aparlosarca strains 55 and 81 in heterokaryotic and homokaryotic hyphal cells. (a) Nuclear conditions of the heterokaryotic hyphal cells of parental strains; (b) Nuclear conditions of the heterokaryotic hyphal cells of the progeny; (c) Nuclear conditions of the homokaryotic hyphal cells of the progeny. Values are expressed as means ± SD of three replicates, and 50 hyphal cells in the apical region were observed in each replicate. According to Duncan's multiple range test, means in the same‐colored bars followed by the same superscripted letter within the observed nuclear conditions in a parental strain/progeny are not significantly different at p < 0.05. Means in the different colored bars followed by the superscripted “*” symbol of the observed binucleate condition between the heterokaryotic progenies are significantly different at p < 0.05, according to the paired‐sample t test. The error bars denote standard deviation