Transcriptomic analysis of engineered and improved Pichia pastoris for S-adenosyl-l-methionine (SAM) production

SAM is the principal methyl group donor in all living organisms, and has attracted much interest in clinical research. We improved SAM production in engineered P. pastoris strain GS115/DS56 by overexpression of the recombinant methionine adenosyltransferase (MAT) gene DS56, and further enhanced SAM prduction in G12-CBS by downregulation of the cystathionine β-synthase (CBS) gene CYS4 with a weak promoter G12. We performed the pairwise transcriptome comparisons between high-producing (HP) and low-producing (LP) strains, in order to understand the impact of SAM accumulation on the P. pastoris physiology and to identify genome-wide targets for further improving SAM production. A twelve array study using total RNA recovered from the LP control strain GS115/3.5K, and the HP strains GS115/DS56 and G12-CBS grown in shake flask at 72 h after methanol induction in the presence of L-Met, as well as from the strain G12-CBS just before L-Met feeding after methanol induction for 24 h. Each chip measures the expression levels of 5777 genes (8 probes per gene).