Fig. 3

Nitrate-dependent β-carotene production in A. nidulans. a Schematic overview of A. nidulans carotenoid production strain TJSF3.1 that harbors the stcM-driven F. fujikuroi ggs1 gene at the yA locus and the stcA/B-driven F. fujikuroi carRA/B genes at the wA locus. b Northern blot expression analysis of indicated genes in the indicated strains. The strains were grown in duplicate for 24 h in 50 mL of GMM with 35 mM glutamine (Gln) as nitrogen source for 24 h at 250 rpm at 37 °C. The mycelia were washed and shifted into new media containing either Gln or NO₃⁻ as nitrogen sources and grown at 250 rpm and 37 °C for 1 h before RNA extraction. RNA was visualized as loading control. c Growth on solid medium demonstrating carotene expression from strain TJSF3.1 and control strain TPMW8.2 grown for 72 h at 37 °C on solidified GMM media containing nitrate as nitrogen source. Bottom picture shows mycelia of the same strains collected from liquid stationary GMM media containing nitrate as nitrogen source grown for 72 h at 37 °C. d HPLC chromatograms at 453 nm of β-carotene extracted from indicate strains grown as described in panel (c). e Quantification of β-carotene produced by TJSF3.1 grown on either NO₃⁻ or glutamine (Gln)