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Morphological novelties, or key innovations, are instrumental to the diversification of the organisms. In plants, one such innovation is the evolution of zygomorphic flowers, which is thought to promote outcrossing and increase flower morphological diversity. We isolated three allelic mutants from twoMimulusspecies displaying altered floral symmetry and identified the causal gene as the ortholog ofArabidopsis BLADE-ON-PETIOLE. We found that MlBOP and MlCYC2A physically interact and this BOP-CYC interaction module is highly conserved across the angiosperms. Furthermore, MlBOP self-ubiquitinates and suppressesMlCYC2Aself-activation. MlCYC2A, in turn, impedes MlBOP ubiquitination. Thus, this molecular tug-of-war between MlBOP and MlCYC2A fine-tunes the expression ofMlCYC2A, contributing to the formation of bilateral symmetry in flowers, a key trait in angiosperm evolution.
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Gene Duplication and Differential Expression of Flower Symmetry Genes in Rhododendron (Ericaceae)
Bilaterally symmetric flowers have evolved over a hundred times in angiosperms, yet orthologs of the transcription factors CYCLOIDEA (CYC), RADIALIS (RAD), and DIVARICATA (DIV) are repeatedly implicated in floral symmetry changes. We examined these candidate genes to elucidate the genetic underpinnings of floral symmetry changes in florally diverse Rhododendron, reconstructing gene trees and comparing gene expression across floral organs in representative species with radial and bilateral flower symmetries. Radially symmetric R. taxifolium Merr. and bilaterally symmetric R. beyerinckianum Koord. had four and five CYC orthologs, respectively, from shared tandem duplications. CYC orthologs were expressed in the longer dorsal petals and stamens and highly expressed in R. beyerinckianum pistils, whereas they were either ubiquitously expressed, lost from the genome, or weakly expressed in R. taxifolium. Both species had two RAD and DIV orthologs uniformly expressed across all floral organs. Differences in gene structure and expression of Rhododendron RAD compared to other asterids suggest that these genes may not be regulated by CYC orthologs. Our evidence supports CYC orthologs as the primary regulators of differential organ growth in Rhododendron flowers, while also suggesting certain deviations from the typical asterid gene regulatory network for flower symmetry.
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- Award ID(s):
- 1911539
- PAR ID:
- 10318045
- Date Published:
- Journal Name:
- Plants
- Volume:
- 10
- Issue:
- 10
- ISSN:
- 2223-7747
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/plants10101994
