Alleles of tangerine Differentially Alter Carotenoid Profiles in Tomato Fruit

Carotenoids are naturally occurring pigments that give tomato (Solanum lycopersicum) fruits their color. Many carotenoids have nutritional benefits as vitamin A precursors, and their consumption is associated with decreased risk for many diseases. Structural and regulatory genes affecting biosynthesis, development and ripening alter the accumulation of specific carotenoids. Alleles of tangerine interrupt the carotenoid pathway by disabling carotenoid isomerase (CRTISO) resulting in the accumulation of bioavailable tetra-cis-lycopene. The tangerine allele t is a deletion spanning the first exon of CRTISO while tangerine virescent (t^v) is a single nucleotide insertion generating a premature stop codon after the second exon. Alleles of the transcription factor RIN regulate the onset of ripening and therefore flux through the carotenoid pathway. To test hypotheses about the effect of allelic variation for tangerine with and without the rin mutation, a segregating population was created, selfed to F5, and analyzed using high performance liquid chromatography. Fruits with t^v accumulated ~1.5x more carotenoids than those with t, with the differential effect detected in both wild-type and rin backgrounds. The rin mutation reduced fruit carotenoid concentrations by ~10x. We hypothesize that alleles of tangerine differentially affect carotenoid pathway flux as a result of a transcript regulated mechanism. Characterization of other metabolic pathways affected by tangerine alleles due to metabolic crosstalk is underway. Studies investigating the transcriptome differences that occur due to allelic variation in tangerine will also help elucidate mechanisms underlying changes in carotenoid biosynthesis and related pathways.