Biology subjects

Onyenedum, J. G.

Publications and source records attributed to Onyenedum, J. G..

6 recordsLinked to original sources

bioRxiv2025

Rampant convergent evolution of vascular oddities and a synnovation characterize the rapid radiation of Paullinieae lianas

Climbing plants have independently evolved thousands of times and are particularly successful in tropical forests, yet their anatomical and evolutionary distinctiveness remains poorly understood. Among the most striking innovations in woody climbers--or "lianas"--are vascular variants: modifications to xylem and phloem that depart from the typical growth found in trees and shrubs. In this work, we leverage the fourth largest lineage of neotropical lianas, Paullinieae (Sapindaceae), to elucidate the evolution of development of vascular variants, and to test key innovation hypotheses in this megadiverse group. We reconstruct the largest phylogeny of any liana lineage to date (227 species, 351 nuclear genes), revealing a rapid radiation in the Miocene. Our anatomical evaluation of 462 species uncovered six patterns of vascular variants spanning three developmental categories--procambial, cambial, and ectopic cambia--which evolved repeatedly across the tree. Using stochastic mapping and a developmental complexity framework, we show that evolutionary transitions from typical growth disproportionately favored developmentally simple variants, suggesting that developmental accessibility constrains macroevolutionary trajectories. Despite the temporal overlap between the disparification of vascular variants, and the diversification rate shift, we find no evidence that vascular variants alone drive species diversification. Instead, diversification rates correlate with the presence of tendrils, climbing growth forms, and zygomorphic flowers. These results suggest a synnovation-- a suite of synergistic innovations rather than a single trait--as the driver of lineage radiation in Paullinieae. Our study highlights how integrating phylogenomics, developmental anatomy, and trait evolution can illuminate the evolutionary mechanisms shaping plant diversity. Significance StatementLianas are functionally distinct from trees and are rising in abundance across neotropical forests. Yet, it remains poorly understood how these plants are developmentally constructed, and what traits underlie their success. Here, we present the largest molecular phylogeny of any climbing plant lineage and show that vascular variants--unusual stem anatomies that enhance flexibility-- are remarkably diverse and have evolved repeatedly in Paullinieae. However, these striking modifications are not linked to species diversification. Instead, we find that the combination of three traits--the climbing habit, coiling tendrils, and zygomorphic flowers--collectively drove the diversification of Paullinieae. Our findings challenge traditional views of key innovations, showing that synergistic trait combinations, rather than any single trait, can catalyze evolutionary radiations and shape biodiversity.

evolutionary biology↗

bioRxiv2025

Phylogenomics of Aristolochia subg. Siphisia (Aristolochiaceae) reveals widespread incomplete lineage sorting and supports a novel pollinator-filtering hypothesis

Aristolochia subgenus Siphisia constitutes a monophyletic lineage of predominantly lianescent species, with occasional shrubs or herbs, and is characterized by remarkable diversity in perianth morphology. Members of Siphisia serve as larval hosts for endangered Lepidoptera and are widely used in traditional medicine. Despite its ecological and ethnobotanical significance, Siphisia systematics remains unresolved due to limited genomic resources and insufficient phylogenetic signal across previously sampled loci. Here, we present a phylogenomically informed framework for Siphisia, integrating 46 newly collected accessions and seven public datasets across 44 taxa. Using genome skimming ([~]30x coverage) and HybPiper, we recovered Angiosperms353 nuclear loci, including supercontigs, for phylogenetic reconstruction via concatenation and coalescent approaches. The resulting species trees resolve seven strongly supported monophyletic clades, each defined by distinct biogeographic patterns and morphological synapomorphies. Comparative plastome analyses from de novo assemblies explored quadripartite structure, plastid phylogeny, GC content, and gene synteny. Cytonuclear discordance was concentrated in species-rich Asian clades, while hybridization signals were rare and limited to deep backbone nodes in North American lineages. These results indicate that incomplete lineage sorting, rather than introgression, accounts for most gene-species tree conflicts and likely reflects strong reproductive isolation following speciation. We also revise a previously taxonomically ambiguous complex--the now well-supported A. versicolor species group--based on integrated phylogenomic and morphological evidence. Within this group, we describe five previously unrecognized cryptic species and identify a novel pollination syndrome involving floral adaptations for pollinator filtering. This syndrome may contribute to prezygotic isolation and recent diversification, and it challenges the prevailing assumption that Aristolochia pollination is universally governed by a trapping-release mechanism--suggesting this model may not apply to subg. Siphisia.

evolutionary biology↗

bioRxiv2025

Helical Growth of Twining Common Bean is Associated with Longitudinal, Not Skewed, Microtubule Patterning

Organ chirality in plants has been linked to cytoskeletal organization, as demonstrated in Arabidopsis thaliana twisted mutants, where left-skewed cortical microtubules are associated with right-handed twisting, and vice versa. While this phenotype seemingly mirrors vining activity, this hypothesis remains understudied within naturally twining plants. Qualitative observations identified skewed microtubules in the twining stem of Ipomoea nil vine, suggesting parallels with Arabidopsis studies. To further investigate organ chirality in twining plants, we used common bean vine (Phaseolus vulgaris L.) to examine the relationship between microtubule orientation, cell morphogenesis, and the right-handed twining phenotype via immunolabeling techniques. Here, we report a transition from mixed microtubules orientations in emergent and elongating internodes to a predominance of longitudinal microtubules in straight and twined stem segments post-elongation. Additionally, we report a distinction in epidermal cell shapes, where the straight portions of the stem consist of lobes with rectangular cells and furrows comprised of round cells, while the twined portions are comprised of cells that are relatively more rectangular and stretched. We propose that these orientations reflect dynamic microtubule responses to external stimuli and growth cues, such as tensile stresses from climbing or tissue expansion. Taken together, these findings highlight dissimilarities between twisting Arabidopsis mutants and naturally twining plants. HighlightLongitudinally arranged cortical microtubules found along the coiled stems of common bean vine highlight disparities between the directional growth of well-documented twisted Arabidopsis mutants and naturally twining plants.

developmental biology↗

bioRxiv2024

Ectopic cambia in Japanese wisteria (Wisteria floribunda) vines are associated with the expression of conserved KNOX genes

Secondary growth is a conserved mechanism that gives rise to vascular tissues produced via a single vascular cambium. Molecular mechanisms underlying this process are characterized mostly in model species bearing typical vascular architecture, while the genetics underlying ecologically-important atypical vascular architectures remain unexplored. We use developmental anatomy, comparative transcriptomics, and molecular evolutionary analyses to address this knowledge gap, investigating how multiple ectopic cambia (EC) form in the woody vine Japanese wisteria. Anatomical studies show EC in Japanese wisteria arise from cortical parenchyma, while cambium-specific transcriptome comparisons reveal that genes acting as regulators of typical cambium development in model species are likewise associated with atypical EC development. Gene trees of KNOX proteins indicate duplication events may contribute to EC formation, including a Fabaceae-specific duplication of KNAT6 detected as under positive selection. These findings reveal insights into the genetics of EC formation, advancing our understanding of the development of complex vascular traits.

plant biology↗

bioRxiv2024

Gelatinous fibers develop asymmetrically for posture support of bends and coils in common bean vine

Gelatinous (G)-fibers are common in the stems of twining vines (twiners), but their role remain unclear given the lack of developmental insights. Here, we characterize the developmental anatomy of G-fiber formation in common bean stems (Phaseolus vulgaris L., Fabaceae). G-fibers in common bean exhibit cell wall organization comparable to other species, consisting of cellulose and Rhamnogalacturonan-I pectins, with possible traces of lignin. We show that G-fibers are absent in the actively circumnutating stems, thus these tensile fibers are not associated with the dynamic searching movements characteristics of twiners. Instead, we found that after a subtle bend or dramatic coil is formed, G-fibers form asymmetrically on the concave side of the stem for posture maintenance. Therefore, G-fibers do not drive movement, but provide support for existing bends, thus stabilizing the helical conformation of twiners around its host to avoid slippage. Finally, we present common bean as an emergent system to study twiners and growth form diversity given its easy cultivation, self-pollination, fast growth, and habit diversity arising from plant breeding, and the ability to induce habit shifts through simple modifications to light conditions.

plant biology↗

bioRxiv2022

Laser Ablation Tomography (LATscan) as a new tool for anatomical studies of woody plants

O_LITraditionally, botanists study the anatomy of plants by carefully sectioning samples, histological staining to highlight tissues of interests, then imaging slides under light microscopy. This approach generates significant details; however, this traditional workflow is laborious and time consuming, and ultimately yields two-dimensional (2D) images. Laser Ablation Tomography (LATscan) is a high-throughput imaging system that yields hundreds of images per minute. This method has proven useful for studying the structure of delicate plant tissues, however its utility in understanding the structure of tougher woody tissues is underexplored. C_LIO_LIWe report LATscan-derived anatomical data from several woody stems (ca. 20 mm) of eight species and compare these results to those obtained through traditional anatomical techniques. C_LIO_LILATscan successfully allows the description of tissue composition by differentiating cell type, size, and shape, but also permits the recognition of distinct cell wall composition (e.g., lignin, suberin, cellulose) based on differential fluorescent signals on unstained samples. C_LIO_LILATscan generate high-resolution 2D images and 3D reconstructions of woody plant samples, therefore this new technology is useful for both qualitative and quantitative analyses. This high-throughput imaging technology has the potential to bolster phenotyping of vegetative and reproductive anatomy, wood anatomy, and other biological systems such as plant-pathogen and parasitic plant associations. C_LI

plant biology↗