Improving antistress capacity and lipid productivity in the green alga Chlorella pyrenoidosa by adding abscisic acid under salt stress conditions

In this study, the regulation of abscisic acid (ABA) on cell growth and lipid biosynthesis was investigated under saltinduced stress in <i>Chlorella</i> pyrenoidosa. It is found that as suffering from only salt stress, although the lipid content of single cell was improved, the inhibitory effects of stress on cell proliferation was visible. When the algal cells were exposed to salt stress and ABA conditions, lipid productivity was increased (45.35 mg L<sup>-1</sup> d<sup>-1</sup>) by 1.17-fold compared to that of control cells (20.91 mg L<sup>-1</sup> d<sup>-1</sup>), and the inhibition to cell growth was relieved. Transcriptomic analysis revealed that after adding ABA, these genes involved in antioxidant activity, jasmonic acid (JA) biosynthesis, and lipid biosynthesis were upregulated. Subsequently, we observed that the levels of glutathione, total antioxidant capacity, trehalose, and JA were elevated and the levels of reactive oxygen species were reduced. This study presents an effective approach to improve lipid production in algal cells, a new mechanism on that ABA alleviates intracellular oxidative stress through JA signaling pathway was elaborated.