Department of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, China Medical University, Taichung, Taiwan.
Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan.
Sci Rep. 2017 Mar 23;7(1):318. doi: 10.1038/s41598-017-00281-x.
Apoptosis is an essential physiological process that controls many important biological functions. However, apoptosis signaling in relation to secondary metabolite biosynthesis in plants and fungi remains a mystery. The fungus Ganoderma lucidum is a popular herbal medicine worldwide, but the biosynthetic regulation of its active ingredients (ganoderic acids, GAs) is poorly understood. We investigated the role of 3',5'-cyclic adenosine monophosphate (cAMP) signaling in fungal apoptosis and GA biosynthesis in G. lucidum. Two phosphodiesterase inhibitors (caffeine and 3-isobutyl-1-methylxanthine, IBMX) and an adenylate cyclase activator (sodium fluoride, NaF) were used to increase intracellular cAMP levels. Fungal apoptosis was identified by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay and a condensed nuclear morphology. Our results showed that GA production and fungal apoptosis were induced when the mycelium was treated with NaF, caffeine, or cAMP/IBMX. Downregulation of squalene synthase and lanosterol synthase gene expression by cAMP was detected in the presence of these chemicals, which indicates that these two genes are not critical for GA induction. Transcriptome analysis indicated that mitochondria might play an important role in cAMP-induced apoptosis and GA biosynthesis. To the best of our knowledge, this is the first report to reveal that cAMP signaling induces apoptosis and secondary metabolite production in fungi.
细胞凋亡是一种重要的生理过程，它控制着许多重要的生物学功能。然而，有关植物和真菌次生代谢产物生物合成与细胞凋亡信号之间的关系仍不清楚。灵芝是一种在全球范围内广泛应用的草药，但人们对其有效成分（灵芝酸，GA）的生物合成调控机制仍知之甚少。我们研究了环磷酸腺苷（cAMP）信号在灵芝细胞凋亡和 GA 生物合成中的作用。我们使用两种磷酸二酯酶抑制剂（咖啡因和 3-异丁基-1-甲基黄嘌呤，IBMX）和一种腺苷酸环化酶激活剂（氟化钠，NaF）来增加细胞内 cAMP 水平。通过末端脱氧核苷酸转移酶介导的 dUTP 缺口末端标记（TUNEL）测定和浓缩核形态学来鉴定真菌凋亡。结果表明，当用 NaF、咖啡因或 cAMP/IBMX 处理菌丝体时，会诱导 GA 产生和真菌凋亡。在这些化学物质存在的情况下，检测到 squalene synthase 和 lanosterol synthase 基因表达下调，这表明这两个基因对于 GA 的诱导并不是关键的。转录组分析表明，线粒体可能在 cAMP 诱导的凋亡和 GA 生物合成中发挥重要作用。据我们所知，这是首次报道 cAMP 信号诱导真菌细胞凋亡和次生代谢产物的产生。
