Characterization of 15--ζ-Carotene Isomerase Z-ISO in Cultivated and Wild Tomato Species Differing in Ripe Fruit Pigmentation.

Isomerization of 9,15,9'-tri--ζ-carotene mediated by 15--ζ-carotene isomerase Z-ISO is a critical step in the biosynthesis of carotenoids, which define fruit color. The tomato clade ( section Lycopersicon) comprises the cultivated tomato () and 12 related wild species differing in fruit color and, thus, represents a good model for studying carotenogenesis in fleshy fruit. In this study, we identified homologous genes, including 5'-UTRs and promoter regions, in 12 cultivars and 5 wild tomato species (red-fruited , yellow-fruited , and green-fruited , , and ). homologs had a highly conserved structure, suggesting that Z-ISO performs a similar function in tomato species despite the difference in their fruit color. transcription levels positively correlated with the carotenoid content in ripe fruit of the tomatoes. An analysis of the promoter and 5'-UTR sequences revealed over 130 -regulatory elements involved in response to light, stresses, and hormones, and in the binding of transcription factors. Green- and red/yellow-fruited species differed in the number and position of -elements, indicating changes in the transcriptional regulation of expression during tomato evolution, which likely contribute to the difference in fruit color.