Cross-talk between gama-aminobutyric acid and calcium ion regulates lipid biosynthesis in Monoraphidium sp. QLY-1 in response to combined treatment of fulvic acid and salinity stress.

In this study, the cross-talk between gama-aminobutyric acid (GABA) and calcium ion (Ca2+) signalling in the regulation of lipid production and cell growth in microalgae under fulvic acid and salinity stress (FA-salinity treatment) was investigated. GABA enhanced the lipid content and lipid productivity rate considerably, which were 1.27 and 1.29 times higher than those of the control, respectively. The levels of biosynthetic gene transcription, GSH, Ca2+ and cellular GABA were promoted by GABA addition, but decreased the ROS levels. Furthermore, the application of Ca2+ also increased lipid synthesis by regulating ROS and GABA signalling and lipogenesis-related genes. These results indicated that cytosolic GABA and Ca2+ levels exert crucial cross-talk in the modulation of cell growth and lipid accumulation induced by FA-salinity treatment. Collectively, this study demonstrated the beneficial effects caused by induction of the combination of chemical compounds on lipid production and provided new insights into lipid synthesis in microalgae.