Effect of glucose on the expression of carotenogenesis genes in mutant strains incapable of synthesizing astaxanthin. Strains: T-YBHH2 (crtYB-/-, white inverted triangle), T-I21H1H (crtI-/-, black square) and T-SHH2 (crtS-/-, white diamond). Levels of mRNA for mature crtYB (a), alternative crtYB (b), mature crtI (c), alternative crtI (d) and crtS (e) in glucose-treated cultures (20 g/l) were determined for each strain relative to the control. The values from wild-type strain UCD-67 385 (wt, black circle) were taken from Figure 1 and are included here as a reference. The dotted line corresponds to the expression value in the control condition. The error bars correspond to standard deviation (n = 3). The negative values on the y-axis denote decreases relative to the control.