Fig. 1

The overall metabolic engineering strategy employed for the construction of a genetically defined l-ABA producer. Central metabolic pathways that contribute to the biosynthesis of l-ABA together with competing pathways and regulatory circuits are shown. The orange shaded boxes represent mutations introduced into the genome. The black Xs indicate the deletion of genes and the red Xs indicate the removal of inhibition or repression. Dotted lines indicate the feedback inhibition. Gray lines indicate the transcriptional attenuation regulation. The red thick arrows indicate the increased flux or activity by directly overexpressing the corresponding genes