Biology subjects

Edwards, M. B.

Publications and source records attributed to Edwards, M. B..

3 recordsLinked to original sources

bioRxiv2022

Complex developmental and transcriptional dynamics underlie pollinator-driven evolutionary transitions in nectar spur morphology in Aquilegia (columbine)

PremiseDetermining the developmental programs underlying morphological variation is key to elucidating the evolutionary processes that generated the stunning biodiversity of the angiosperms. Here, we characterize the developmental and transcriptional dynamics of the elaborate petal nectar spur of Aquilegia (columbine) in species with contrasting pollination syndromes and spur morphologies. MethodsWe collected petal epidermal cell number and length data across four Aquilegia species, two with the short, curved nectar spurs of the bee-pollination syndrome, and two with the long, straight spurs of the hummingbird syndrome. We also performed RNA-seq on A. brevistyla (bee) and A. canadensis (hummingbird) distal and proximal spur compartments at multiple developmental stages. Finally, we intersected these datasets with a previous QTL mapping study on spur length and shape to identify new candidate loci. ResultsThe differential growth between the proximal and distal surfaces of curved spurs is primarily driven by differential cell division. However, independent transitions to straight spurs in the hummingbird syndrome have evolved by increasing differential cell elongation between spur surfaces. The RNA-seq data reveal these tissues to be transcriptionally distinct, and point to auxin signaling as being involved with the differential cell elongation responsible for the evolution of straight spurs. We identify several promising candidate genes for future study. ConclusionsOur study, taken together with previous work in Aquilegia, reveals the complexity of the developmental mechanisms underlying trait variation in this system. The framework we have establish here will lead to exciting future work examining candidate genes and processes involved in the rapid radiation of the genus.

plant biology↗

bioRxiv2021

Genetic architecture underlying variation in floral meristem termination in Aquilegia

Floral organs are produced by floral meristems (FMs), which harbor stem cells in their centers. Since each flower only has a finite number of organs, the stem cell activity of a FM will always terminate at a specific time point, a process termed floral meristem termination (FMT). Variation in the timing of FMT can give rise to floral morphological diversity, but how this process is fine-tuned at a developmental and evolutionary level is poorly understood. Flowers from the genus Aquilegia share identical floral organ arrangement except for stamen whorl numbers (SWN), making Aquilegia a well-suited system for investigation of this process: differences in SWN between species represent differences in the timing of FMT. By crossing A. canadensis and A. brevistyla, quantitative trait locus (QTL) mapping has revealed a complex genetic architecture with seven QTL. We identified potential candidate genes under each QTL and characterized novel expression patterns of select candidate genes using in situ hybridization. To our knowledge, this is the first attempt to dissect the genetic basis of how natural variation in the timing of FMT is regulated and our results provide insight into how floral morphological diversity can be generated at the meristematic level.

plant biology↗

bioRxiv2021

Genetic architecture of floral traits in bee- and hummingbird-pollinated sister species of Aquilegia (columbine)

Interactions with animal pollinators have helped shape the stunning diversity of flower morphologies across the angiosperms. A common evolutionary consequence of these interactions is that some flowers have converged on suites of traits, or pollination syndromes, that attract and reward specific pollinator groups. Determining the genetic basis of these floral pollination syndromes can help us understand the processes that contributed to the diversification of the angiosperms. Here, we characterize the genetic architecture of a bee-to-hummingbird pollination shift in Aquilegia (columbine) using QTL mapping of 17 floral traits encompassing color, nectar composition, and organ morphology. In this system, we find that the genetic architectures underlying differences in floral color are quite complex, and we identify several likely candidate genes involved in anthocyanin and carotenoid floral pigmentation. Most morphological and nectar traits also have complex genetic underpinnings; however, one of the key floral morphological phenotypes, nectar spur curvature, is shaped by a single locus of large effect.

plant biology↗