Abstract
Background Polyporus umbellatus sclerotia have been used as a diuretic agent in China for over two thousand years. A shortage of the natural P. umbellatus has prompted researchers to induce sclerotial formation in the laboratory.Methodology/Principal Finding P. umbellatus cultivation in a sawdust-based substrate was investigated to evaluate the effect of low temperature conditions on sclerotial formation. A phenol-sulfuric acid method was employed to determine the polysaccharide content of wild P. umbellatus sclerotia and mycelia and sclerotia grown in low-temperature treatments. In addition, reactive oxygen species (ROS) content, expressed as the fluorescence intensity of mycelia during sclerotial differentiation was determined. Analysis of ROS generation and sclerotial formation in mycelia after treatment with the antioxidants such as diphenyleneiodonium chloride (DPI), apocynin (Apo), or vitamin C were studied. Furthermore, macroscopic and microscopic characteristics of sclerotial differentiation were observed. Sclerotia were not induced by continuous cultivation at 25°C. The polysaccharide content of the artificial sclerotia is 78% of that of wild sclerotia. In the low-temperature treatment group, the fluorescent intensity of ROS was higher than that of the room temperature (25°C) group which did not induce sclerotial formation all through the cultivation. The antioxidants DPI and Apo reduced ROS levels and did not induce sclerotial formation. Although the concentration-dependent effects of vitamin C (5–15 mg mL−1) also reduced ROS generation and inhibited sclerotial formation, using a low concentration of vitamin C (1 mg mL−1) successfully induced sclerotial differentiation and increased ROS production.Conclusions/SignificanceExposure to low temperatures induced P. umbellatus sclerotial morphogenesis during cultivation. Low temperature treatment enhanced ROS in mycelia, which may be important in triggering sclerotial differentiation in P. umbellatus. Moreover, the application of antioxidants impaired ROS generation and inhibited sclerotial formation. Our findings may help to provide new insights into the biological mechanisms underlying sclerotial morphogenesis in P. umbellatus.
Highlights
Polyporus umbellatus (Pers.) Fr., one of the most precious and widely used medicinal fungi, belong to the Polyporaceae family of Basidiomycota phylum [1,2]
On the 90th day, the initial sclerotia with spherical or irregular forms increased in size and were often accompanied with transparent exudate droplet; the surface color turned to grey-white, and the mycelia on the surface were much denser compared with the sclerotial initiation (SI) stage
Temperature shift treatment was used to induce the formation of P. umbellatus sclerotia
Summary
Polyporus umbellatus (Pers.) Fr., one of the most precious and widely used medicinal fungi, belong to the Polyporaceae family of Basidiomycota phylum [1,2]. P. umbellatus sclerotia have been shown to possess pharmacological activities for the treatment of conditions such as acute nephritis and edema [3]. The antitumor properties of polysaccharides isolated from P. umbellatus sclerotia have been well documented for over 30 years [4]. Many reports have focused on the treatment of certain cancers, including leukemia [5], liver cancer [6], using active constituents isolated from P. umbellatus. Polyporus umbellatus polysaccharide has been demonstrated to possess the immunostimulating, anti-inflammatory and hepatoprotective properties [9,10,11,12,13]. Polyporus umbellatus sclerotia have been used as a diuretic agent in China for over two thousand years. A shortage of the natural P. umbellatus has prompted researchers to induce sclerotial formation in the laboratory
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