Figure 7.

A model of carotenogenesis under the effect of three alleles of CmOr and of a dysfunctional CRTISO. In the presence of both OR-His and OR-Arg, carotenoid pathway flux occurs at high levels (green arrows) but only OR-His prevents further metabolism downstream of β-carotene (red arrow), resulting in strongly increased β-carotene accumulation in OR-His melon fruits but not in OR-Arg. In contrast, low PSY protein levels, caused by a truncated OR-lowβ, results in a weak pathway flux (red arrow) and, hence, low carotenoid levels in OR-lowβ fruit. Dysfunctional CRTISO in yofi melons results in metabolic arrest downstream of prolycopene (red arrow). Accordingly, prolycopene is accumulated in yofi genotypes regardless of the golden SNP, which operates downstream in the pathway.