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Enhanced production of perylenequinones in the endophytic fungus Shiraia sp. Slf14 by calcium/calmodulin signal transduction
- Liu, Bin, Bao, Jianying, Zhang, Zhibin, Yan, Riming, Wang, Ya, Yang, Huilin, Zhu, Du
- Applied microbiology and biotechnology 2018 v.102 no.1 pp. 153-163
- biosynthesis, calcium, calcium signaling, calmodulin, endophytes, gene expression regulation, genes, mycotoxins, plant pathogenic fungi, polyketides, reactive oxygen species
- Perylenequinones (PQ) that notably produce reactive oxygen species upon exposure to visible light are a class of photoactivated polyketide mycotoxins produced by fungal plant pathogens such as Shiraia sp. The involvement of Ca²⁺/calmodulin (CaM) signalling in PQ biosynthesis was investigated by submerged culturing of Shiraia sp. Slf14, a species that produces hypocrellins HA and HB and elsinochromes EA, EB, and EC. Our results showed that the total content of PQ reached 1894.66 ± 21.93 mg/L under optimal conditions of Ca²⁺ addition, which represents a 5.8-fold improvement over controls. The addition of pharmacological Ca²⁺ sensor inhibitors strongly inhibited PQ production, which indicates that Ca²⁺/CaM signalling regulates PQ biosynthesis. The expression levels of Ca²⁺ sensor and PQ biosynthetic genes were downregulated following addition of inhibitors but were upregulated upon addition of Ca²⁺. Inhibition was partially released by external Ca²⁺ supplementation. Fluo-3/AM experiments revealed that similar cytosolic Ca²⁺ variation occurred under these conditions. These results demonstrated that Ca²⁺ signalling via the CaM transduction pathway plays a pivotal role in PQ biosynthesis.