Integration of a multi-step heterologous pathway in Saccharomyces cerevisiae for the production of abscisic acid

Abstract

AbstractBackgroundThe sesquiterpenoid abscisic acid (ABA) is mostly known for regulating developmental processes and abiotic stress responses in higher plants. Recent studies show that ABA also exhibits a variety of pharmacological activities. Affordable and sustainable production will be required to utilize the compound in agriculture and as a potential pharmaceutical.Saccharomyces cerevisiaeis an established workhorse for the biotechnological production of chemicals. In this study, we constructed and characterised an ABA-producingS. cerevisiaestrain using the ABA biosynthetic pathway fromBotrytis cinerea.ResultsExpression of theB. cinereagenesbcaba1,bcaba2,bcaba3andbcaba4was sufficient to establish ABA production in the heterologous host. We characterised the ABA-producing strain further by monitoring ABA production over time and, since the pathway contains two cytochrome P450 enzymes, by investigating the effects of overexpressing the nativeS. cerevisiaeor theB. cinereacytochrome P450 reductase. Both, overexpression of the native or heterologous cytochrome P450 reductase, led to increased ABA titres. We were able to show that ABA production was not affected by precursor or NADPH supply, which suggested that the heterologous enzymes were limiting the flux towards the product. TheB. cinereacytochrome P450 monooxygenases BcABA1 and BcABA2 were identified as pathway bottlenecks and balancing the expression levels of the pathway enzymes resulted in 4.1-fold increased ABA titres while reducing by-product formation.ConclusionThis work represents the first step towards a heterologous ABA cell factory for the commercially relevant sesquiterpenoid.