Fig. 3

CRISPR–Cas9 system mediated asm25 gene inactivation in A. pretiosum. A Sanger sequencing chromatograms for mutant MD01, the ΦC31 attB replaced asm25 gene sequence showing in grey. B Comparison of AP-3 production of mutant MD01 and parent strain L40. MD01, mutant with asm25 deletion. A roughly 14.5% increase in AP-3 production for MD01 compared to that of strain L40. C Marker-free mutant screening. Colonies were inoculated into YMG plate with thiostrepton and without antibiotics, respectively, to verify the curing of plasmid