Characterizatons in brown film formation of edible mushroom Lentinula edodes
【摘要】：Lentinula edodes is the most production and trading mushroom in China. The agricultural cultivation of L. edodes includes the vegetative mycelial growth, brown film formation, primordium initiation, and fruiting body development. The formation of brown film is a process of pigment accumulation on the surface of mature mycelium, and this process is critical for maintaining water contents in the medium and ensuring a high quantity and quality of fruiting body formation. Additionally, it can protect inner mycelia from pathogenic organisms and ultraviolet radiation. In this study, UV, IR, and elemental analysis were used to reveal that the pigment composition in the brown film was melanin. SEM and TEM were used to systematically analyze melanin size,morphological characteristics, accumulations, melanogenesis, and a series of subcellular structural changes during brown film formation. The results indicated that L. edodes melanins were nearly nano particles, and present in cells in three forms, viz, melanin granules, melanin vesicles, and melanin polymer. The accumulations of melanin on the cell wall was followed plasmolysis, protoplast membrane broken, melanin accumulated in the interstitial space, and gradually accumulated on the outer cell wall. In addition, a fibrous melanosome-like body which was similar to melanosome in mammalian melanoma and melanocytes has been observed in melanogenesis of L.edodes. A series of dolipore septum degradations and autophagy phenomenon(autophagosome formation,mitophagy, ER-phagy) has been observed in browning process. In the final stage of browning, the dolipore septum was disappeared, moreover, the entire cell was usually left with the vesicles remaining after autophagy, as well as the fragmented ER. This study provided a foundation for further revealing the key factors and regulation of brown film formation in L. edodes.