Overexpression of RmLCYB from Rhododendron molle increases carotenoid in Nicotiana tabacum

Rhododendron molle G. Don is a deciduous species of Rhododendron with unique yellow flowers. Carotenoids play a major role in flower coloration. Lycopene β-cyclase (LCYB) is an essential enzyme which catalyzes the synthesis of β-carotene from lycopene in the carotenoid biosynthesis pathway. However, the molecular function of the LCYB gene in R. molle remains unknown. In this study, the RmLCYB gene was first isolated from R. molle . The RmLCYB protein sequence showed high similarity with LCYB in other plant species. RmLCYB is expressed in petals during flower development and reaches the highest level at the initial flowering stage . The main content of carotenoid in R. molle flower is β-carotene. To verify the function of RmLCYB , we overexpressed RmLCYB in tobacco. We found that the total content of carotenoid in the transgenic tobacco with overexpression of RmLCYB gene increased 1.73-fold compared with the wild-type tobacco. The results indicate that the RmLCYB gene can enhance the carotenoid content and alter flower color. This gene has the potential to promote carotenoid synthesis and improve our ability to create evergreen azaleas with desirable yellow flower.