虎奶菇菌核含有大量的超支化β-葡聚糖和糖蛋白等活性成分,具有抗肿瘤,提高免疫力等多种功能,但仅靠袋料栽培存在周期长、效率低、成本高等问题。该文探究了平板培养过程中温度和pH对虎奶菇菌核形成的影响,发现在菌丝长满PDA平板后生成菌核的最适温度为25 ℃,最适pH值为5,经过30 d培养可获得菌核。研究发现,菌核中过氧化氢浓度显著低于菌丝,但过氧化氢酶活力则显著高于菌丝。培养基中适当浓度的过氧化氢可通过引发胞内的氧化应激而促进菌核的形成,但抗坏血酸则可消除胞内的氧化应激而抑制菌核的形成。实时荧光定量PCR(real-time quantitative polymerase chain reaction,RT-qPCR)试验表明,菌核的形成过程与过氧化氢酶、细胞壁合成和丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)均有一定关系。因此,温度、pH和氧化还原环境等外界条件的变化会引起菌丝细胞内活性氧浓度的升高,当升高至一定量时,胞内产生氧化应激,进而触发菌丝细胞的分化和菌核的形成。
Due to a mass of hyperbranched β-glucan, glycoprotein and other active substances in sclerotia of Pleurotus tuber-regium, it has several biological functions, such as anti-tumor, immuno-modulatory, and so on. However, they could only be produced by bag cultivation, which has the disadvantages of a long cultivation period, low efficiency, and high cost. This work used a petri dish containing potato dextrose agar to cultivate P. tuber-regium sclerotia in a simple and fast method. The sclerotia could be optimally developed after 30 days cultivation at 25 ℃ and pH 5. Although the quantity of H2O2 in sclerotia cells was lower than that in mycelia, catalase activity had the opposite effect. The findings showed that optimum quantity of H2O2 in culture medium might cause intracellular oxidative stress and promote sclerotia development, whereas ascorbic acid could prevent sclerotia formation by removing intracellular oxidative stress. RT-qPCR experiment revealed that catalase activity, cell wall synthesis and the MAPK pathway were all involved in the production of sclerotia. The concentration of reactive oxygen species (ROS) in mycelial cells would increase when the external temperature, pH and redox environment changed. When the quantity of ROS reached a particular threshold, intracellular oxidative stress would ensue, triggering the cell to differentiate into sclerotium.
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