Identification and Characterization of Transcription Factors Regulating Carotenoid Pigmentation During Mimulus Flower Development

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Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers (e.g., daffodils, daylilies, sunflowers) and fruits (e.g., oranges, tomatoes, mangos). They serve an important function in the ecology and evolution of plants as visual pigments to attract animals for pollination and seed dispersal. The tremendous diversity of carotenoid pigmentation patterns found in flowers and fruits is primarily determined by regulatory genes that control when and where the carotenoid pigments are produced. However, little is known about the identity and function of these regulatory genes. This study employs a new plant genetic model system, monkeyflowers, to identify carotenoid-regulating genes and to characterize their function. The discovery and characterization of these regulatory genes are crucial to understanding how carotenoid production is controlled during flower development and how carotenoid-based flower color variation is generated during evolution. From a practical perspective, because carotenoids are also essential components of human diets as precursors for vitamin A biosynthesis, the regulatory genes discovered in this study have the potential for high translational impact in plant breeding to enhance carotenoid production in crop plants. The plant materials will be incorporated into a live plant exhibit at the University of Connecticut to demonstrate concepts of genetics and evolution for student and public education. Furthermore, the flower images, pollination videos, and interactive, multimedia illustrations resulting from this project will be developed into a new Plant Biology section on the nationally and internationally recognized Learn.Genetics website as online educational resources. This study leverages recently developed genomic resources, stable transgenic tools, and chemically induced mutants of monkeyflowers (Mimulus) to identify and characterize transcription factors that regulate flower carotenoid pigmentation. Results from preliminary work in the PIs laboratory allows the formulation of the central hypothesis: a transcriptional regulatory complex, containing at least an R2R3-MYB and a tetratricopeptide repeat (TPR) protein, directly activates carotenoid biosynthetic genes during flower development in Mimulus, and differential expression of the regulatory genes contributes to pigment pattern variation between species. In this proposed project, additional components of the transcriptional regulatory complex will be identified by bulk segregant analysis of another non-allelic mutant and by yeast two-hybrid screening using the MYB and TPR proteins as baits. The functional mechanisms of the MYB and TPR genes in the regulation of carotenoid pigmentation will be determined by protein-protein and protein-DNA interaction assays. The role of these regulatory genes in producing flower color variation will be examined by gene expression analysis and transgenic experiments in Mimulus species that display distinct carotenoid pigmentation patterns.