Plasmid construction and gene knockout related to tryptophan accumulation. The black dotted line indicates repression. The red cross indicates the target genes to be knocked out. The pink and blue colors indicate the upstream pathway of tryptophan accumulation, which was improved, and the downstream pathway of violacein production from tryptophan, which was introduced, respectively. E4P, erythrose 4-phosphate; PEP, phosphoenolpyruvate; DS, 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase; DAHP, 3-deoxy-D-arabinoheptulosonate 7-phosphate; CM, chorismate mutase; CA, chorismic acid; Phe, phenylalanine; Tyr, tyrosine; Trp, tryptophan; Vio, violacein, Devio, deoxyviolacein.