Overexpression of S-R enhances the accumulation of biomass, fatty acids, and β-carotene in Schizochytrium.

Strategies for enhancing biomass accumulation and increasing the production of fatty acids and β-carotene in Schizochytrium are hindered by the lack of suitable targets. In this study, S-R, a RING (really interesting new gene) finger domain-containing protein, was identified in Schizochytrium, with homologs found in the family Thraustochytriaceae. Transgenic strains overexpressing S-R showed a minor improvement in cell growth but a significant increase in total fatty acids content by 1.29- to 1.36-fold. Almost all individual saturated fatty acids exhibited significant increases, with the greatest increase observed in the C14:0 content, by 1.52- to 1.78-fold. Additionally, the β-carotene content of S-R strains was significantly upregulated. Overexpression of s-r conferred hypersaline tolerance in Schizochytrium, with a significant increase in dry cell weight, total fatty acids and β-carotene, likely due to the upregulation of glycerol and proline. This study provides a feasible strategy to engineer Thraustochytriaceae for efficient biomass and biochemical production.