Understanding the inhibitory mechanism of antialgal allelochemical flavonoids from genetic variations: Photosynthesis, toxin synthesis and nutrient utility

Flavonoids are natural polyphenolic compounds from plants. As a new biotechnological algaecide, the molecular mechanism of plant flavonoids on the inhibition of Microcystis aeruginosa is still unknown. Therefore, in this study, we analyzed the variation of expressions of photosynthesis-related genes, microcystin synthesis-related genes and the genes involved in N and P acquisition in M. aeruginosa under the flavonoids stress. The results showed that the expression of psb D1, psa B and rbc L related to photosynthesis were influenced by three flavonoids but with different changing tendencies. The transcription of mcy A, mcy D and mcy H related to microcystin synthesis were decreased after 5-d of exposure, which could block microcystin synthesis. Meanwhile, flavonoids treatments resulted in the inhibition of N and P acquisition related genes transcription to affect the absorption of N and P in algal cells, and further influenced the physiological metabolic process of M. aeruginosa .