Hypocrellins are main perylenequinone pigments isolated from fruit-bodies of bambusicolous Shiraia fungi, which have been used in traditional Chinese medicine. Hypocrellin A (HA) and B (HB) are developed as new non-porphyrin and reactive oxygen species (ROS)-generating photosensitizers in photodynamic therapy (PDT) for cancers, viruses and infectious microbes [1]
[2]. Shiraia mycelium culture has become a promising production process of the new PDT agents [3]
[4]. Nitric oxide (NO) is an important signal molecule to elicit the production of secondary metabolites in plant stress responses [5]. In this study, sodium nitroprusside (SNP) was used as a NO donor to induce hypocrellin production in Shiraia mycelium cultures. SNP application could not only enhance HA content by 178.96% in mycelia, but also stimulate its efflux to the medium. SNP acted as a pro-oxidant by up-regulating the gene expression and activity of (ROS) generating NADPH oxidase (NOX) and antioxidant enzymes. Moreover, SNP treatment increased the proportion of total unsaturated fatty acids in the hypha membranes and enhanced membrane permeability. Gene ontology (GO) analysis revealed that SNP treatment could up-regulate biosynthetic genes for hypocrellins and activate the transporter protein major facilitator superfamily (MFS) for the exudation. The results can facitate further understanding signaling moleculues in the hypocrellin biosynthesis and provide a practical biotechnological strategy for enhanced hypocrellin production.
