Format: ORAL

Estefania Elejalde-Baena1, Favio Gonzalez2, Juan F. Alzate3, Natalia Pabon-Mora1

1 University of Antioquia, Medellin, Colombia, 2 National University of Colombia, Bogota, Colombia, 3 National Center of Genomic Sequencing – CNSG, Medellin, Colombia

Chlorophylls, carotenoids, flavonoids, and betalains generate colors in plants. Anthocyanins, a type of flavonoids, are the pigments responsible for red, pink, and purple hues in vegetative and reproductive tissues of plants. The synthesis of these pigments is primarily regulated at the transcriptional level by R2R3-MYB transcription factors assigned to subgroup 6. These genes have extensively studied in model plants such as Arabidopsis thaliana, Antirrhinum majus, and Petunia hybrida. In this study, we focused on a system composed by the endoholoparasite Pilostyles boyacensis and its exclusive host Dalea cuatrecasasii, both exhibiting purple perianth organs. Two R2R3-MYB homologs from subgroups 5 and 7 were identified in P. boyacensis, and four homologs from subgroup 6 were isolated from Dalea cuatrecasasii. We found that R2R3 MYB genes from subgroups 5 and 7 are actively expressed in the endophyte, flowers, and fruits of P. boyacensis. Meanwhile, R2R3 MYB subgroup 6 homologs are expressed in the in the D. cuatrecasasii inflorescences, as expected. Interestingly, R2R3 MYB S6 homologs were also found expressed in the P. boyacensis endophyte. These results suggest that anthocyanin synthesis in the flowers and fruits of the holoparasite P. boyacensis may be mediated by host-specific R2R3 MYB S6 genes, which are known to be mobile at least, from Citrus to Cuscuta. Alternatively, anthocyanins in P. boyacensis can be endogenously produced R2R3 MYB genes from subgroups 5 and 7. We discuss our results in the broader context of convergent floral pigments and the resulting color hues in parasites with significant reduction in their body plan and complete dependence upon their hosts.