Once in a blue moon: an unexpected evolutionary route to blue floral pigmentation in orchids
- 1Adelaide University
Abstract
Blue flowers are rare in the hyperdiverse orchid family, and the genetic mechanisms enabling their blue delphinidin-based pigmentation remain poorly understood. Within the Australian orchid subtribe Caladeniinae (~350 spp.), repeated transitions from maroon to blue flowers, followed by reversions to maroon, provide a unique opportunity to investigate blue flower evolution. Using phylotranscriptomics, anthocyanin profiling, molecular evolutionary analyses, and gene expression data from 51 species, we reconstructed the genetic changes associated with these transitions. Despite its near-universal role in delphinidin biosynthesis across flowering plants, unexpectedly, we found no evidence for a functional CYP75A-mediated flavonoid 3'5'-hydroxylase (F3'5'H) pathway. Instead, blue-flowered species possess a duplicated CYP75B lineage gene (CYP75B-D) with apparent 5'-hydroxylase activity, a derived D-type dihydroflavonol reductase (DFR), and a distinct anthocyanin biosynthetic pathway co-expression pattern. Phylogenetic analyses suggest that the D-type DFR pre-dated blue flower evolution, representing a permissive evolutionary shift later coupled with the evolution of CYP75B-D. Notably, blue flower evolution coincided with repeated pollinator transitions and major palaeoenvironmental change during the Middle Miocene. Together, these findings reveal an unexpected route to blue floral pigmentation and suggest that its evolution arose through the interaction of molecular innovation, regulatory evolution, and ecological opportunity.
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BibTeX
@misc{john2026once,
title = {{Once in a blue moon: an unexpected evolutionary route to blue floral pigmentation in orchids}},
author = {E. John and R. O'Donnell and J. Perkins and M. Ruibal and T. Mizuno and R. Peakall and D. Wong},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.20.760294},
url = {https://www.biorxiv.org/content/10.64898/2026.10.20.760294v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Once in a blue moon: an unexpected evolutionary route to blue floral pigmentation in orchids
AU - E. John
AU - R. O'Donnell
AU - J. Perkins
AU - M. Ruibal
AU - T. Mizuno
AU - R. Peakall
AU - D. Wong
PY - 2026
DA - 2026/10/20
PB - bioRxiv
DO - 10.64898/2026.10.20.760294
UR - https://www.biorxiv.org/content/10.64898/2026.10.20.760294v1
AB - Blue flowers are rare in the hyperdiverse orchid family, and the genetic mechanisms enabling their blue delphinidin-based pigmentation remain poorly understood. Within the Australian orchid subtribe Caladeniinae (~350 spp.), repeated transitions from maroon to blue flowers, followed by reversions to maroon, provide a unique opportunity to investigate blue flower evolution. Using phylotranscriptomics, anthocyanin profiling, molecular evolutionary analyses, and gene expression data from 51 species, we reconstructed the genetic changes associated with these transitions. Despite its near-universal role in delphinidin biosynthesis across flowering plants, unexpectedly, we found no evidence for a functional CYP75A-mediated flavonoid 3'5'-hydroxylase (F3'5'H) pathway. Instead, blue-flowered species possess a duplicated CYP75B lineage gene (CYP75B-D) with apparent 5'-hydroxylase activity, a derived D-type dihydroflavonol reductase (DFR), and a distinct anthocyanin biosynthetic pathway co-expression pattern. Phylogenetic analyses suggest that the D-type DFR pre-dated blue flower evolution, representing a permissive evolutionary shift later coupled with the evolution of CYP75B-D. Notably, blue flower evolution coincided with repeated pollinator transitions and major palaeoenvironmental change during the Middle Miocene. Together, these findings reveal an unexpected route to blue floral pigmentation and suggest that its evolution arose through the interaction of molecular innovation, regulatory evolution, and ecological opportunity.
ER -