Fig. 6

a Diagram of the proposed model for β-carotene synthesis in GR-host, b gene construct of β-carotene synthesis, which includes CrtE (GGPP synthase), CrtB (phytoene synthase), CrtI (phytoene desaturase), and CrtY (lycopene cyclase), all together abbreviated as CrtEBIY. (c) β-carotene production in GR-host and its wildtype control (CrtEBIY) and vector control (CrtEBIY/pET32a) (****: p-value < 0.0001, done with t-test, average based on five technological repeats). The product of β-carotene was extracted with acetone and measured in the absorbance wavelength (458 nm). The comparison between wildtype control and vector control with GR-host suggested that GR altogether facilitated the synthesis of β-carotene