Engineering an Efficient Expression Using Heterologous Promoters and Transcriptional Activators in .

Galactose-inducible () promoters have been widely used in metabolic engineering in for production of valuable products. Endogenous promoters and transcription factors have often been engineered to improve promoter activities. Heterologous promoters and activator (Gal4p-like transcriptional activators), although existing in other yeasts or fungi, have not been well explored. In this study, we comprehensively characterized the activation effects of Gal4p activators from different yeasts or fungi on a variant of promoters. Overexpressing endogenous Gal4p driven by P increased the activities of native P and heterologous P by 131.20% and 72.45%, respectively. Furthermore, eight transcriptional activators from different organisms were characterized and most of them exhibited functions that were consistent with Gal4p. Expression of Lac9p from further increased the activity of P and P by 41.56% and 100.63%, respectively, compared to Gal4p expression, and was able to evade Gal80p inhibition. This optimized expression system can be used to increase the production of β-carotene by 9.02-fold in . Our study demonstrated that a combination of heterologous transcriptional activators and promoters provided novel insights into the optimization of the expression system.