Functional Analysis of the Marigold (Tagetes erecta) Lycopene ε-cyclase (TeLCYe) Promoter in Transgenic Tobacco.

Lycopene ε-cyclases (LCYEs) are key enzymes in carotenoid biosynthesis converting red lycopene to downstream lutein. The flowers of marigold (Tagetes erecta) have been superior sources to supply lutein. However, the transcriptional regulatory mechanisms of LCYe in lutein synthesis are still unclear in marigold. In this work, the expression pattern of the TeLCYe gene in marigold indicated that TeLCYe mainly expressed in floral organs. To gain a better understanding of the expression and regulatory mechanism of TeLCYe gene, the TeLCYe promoter was isolated, sequenced, and analyzed through bioinformatics tools. The results suggested that the sequence of TeLCYe promoter contained various putative cis-acting elements responsive to exogenous and endogenous factors. The full-length TeLCYe promoter and three 5'-deletion fragments were fused to the GUS reporter gene and transferred into tobacco to test the promoter activities. A strong GUS activity was observed in stems of seedlings, leaves of seedlings, middle stems, top leaves, petals, stamens, and stigmas in transgenic tobacco containing full-length TeLCYe promoter LP0-2086. Deletion of - 910 to - 429 bp 5' to ATG significantly increased the GUS activity in chloroplast-rich tissues and floral organs, while deletion occurring from 1170 to 910 bp upstream ATG decreased the TeLCYe promoter strength in stems of seedlings, leaves of seedlings, top leaves and sepals. Functional characterization of the full-length TeLCYe promoter and its' deletion fragments in stable transgenic tobacco indicated that the LP0-2086 contains some specific cis-acting elements, which might result in the high-level expression of in floral organs, and LP2-910 might contain some specific cis-acting elements which improved GUS activities in vegetable tissues.