Flavonol-regulating MYB underlies the evolution of red flowers in Iochroma (Solanaceae)

This is a Preprint and has not been peer reviewed. This is version 5 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 5 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Anthocyanins, the pigments that give rise to blue, purple, red and pink colors in many flowers and fruits, are produced by the deeply conserved flavonoid biosynthesis pathway. The regulation of this pathway is thus fundamental for species differences in color across flowering plants, and a growing body of evidence implicates MYB transcription factors as key players activating or suppressing the production of different pigments. Nevertheless, the potential role of MYBs genes in determining the type of pigment produced (as opposed to the overall amount) is unknown. Here we demonstrate that a lineage of R2R3 MYBs that is closely related to well- known flavonol regulators (MYB12 members in subgroup 7) is the primary determinant of the shift from blue to red flowers in the genus Iochroma. Similar to its ortholog in Capsicum, this Iochroma MYB12-like gene controls the expression of flavonoid-3’-hydroxylase, the pathway branch point between red and blue pigments, and when down-regulated, results in redirection of flux toward red pigments. These results underscore the importance of transcription factor evolution in generating phenotypic novelty as well as the competitive nature of interactions among flavonoid pathway branches. In addition, our study demonstrates the effectiveness of RNAseq of segregating populations, in combination with other lines of evidence, for identifying novel functional variation. https://doi.org/10.32942/X22P85 Ecology and Evolutionary Biology, Genetics and Genomics, Life Sciences, Plant Sciences Transcriptomics, flavonoid biosynthesis, pigmentation, flower color, pelargonidin, gene regulation, flavonoid biosynthesis, pigmentation, flower color, pelargonidin, gene regulation Published: 2025-03-13 17:14 Last Updated: 2025-09-22 15:00 CC-By Attribution-ShareAlike 4.0 International Conflict of interest statement: None Data and Code Availability Statement: RNA-seq data from the backcross individuals have been uploaded to the SRA under Bioproject PRJNA1092111. Data for the other six species have been uploaded to SRA Bioproject PRJNA1102413. Code and additional data used in the analyses are available at https://osf.io/j5m8f/. Language: English