Biology subjects

Acevedo, A. A.

Publications and source records attributed to Acevedo, A. A..

5 recordsLinked to original sources

bioRxiv2026

A primordium-level ice barrier in Vaccinium corymbosum floral buds is lost as their xylem trace matures

Flower primordia of Vaccinium corymbosum L. (highbush blueberry) exclude ice formation in winter through an unexplained biological barrier despite lignified xylem connecting them to the stem. We asked where this barrier lies and whether the maturation of that connection, rather than its presence, tracks its seasonal loss. On buds collected in fall, winter and spring we combined structure-resolved freezing tests, water content, thermal analysis, cryomicroscopy and xylem anatomy. Whole-bud LT50 was -20 C in fall, -31 C in winter, and -16 C in spring; water content rose only in spring. Buds froze extraorgan, without low-temperature exotherms to -46 C. Ice nucleated in the stem, reached the bud within minutes and accumulated in the scales. The bud axis froze in every season, whereas the primordia stayed ice-free in fall and winter and froze in spring, placing the barrier at each primordium, not the bud base. A continuous xylem trace reached every primordium in every season; its elements were mostly annular and helical until spring, when scalariform, reticulate and pitted elements predominated. Junction conduits stayed narrow (2 to 3 um). The primordium-level barrier was lost as this trace matured; we propose that its immature state is part of the long-unexplained barrier.

plant biology↗

bioRxiv2025

Brassinosteroid treatment reveals the importance of xyloglucan transglucosylase/hydrolase (XTH) genes in growth habit determination of twining common bean vines

O_LIBrassinosteroids impact the development of G-fibers --specialized cells that generate tension in plants. To explore the functional and genetic relationships between G-fibers and twining stems of common bean, we applied an active brassinosteroid and a brassinosteroid inhibitor to perturb G-fiber development and probed these phenotypes through gene expression and anatomical analyses. C_LIO_LIBrassinosteroid treatment generated phenotypes that aKected the three key features of twining: elongation, circumnutation, and G-fiber development. We examined anatomical and biochemical changes in the G-fibers through cross-sections, macerations, and immunohistochemistry. RNA sequencing and differential gene expression analysis allowed us to identify unique gene expression patterns for each treatment. C_LIO_LIBrassinosteroid treatment led to significantly elongated internodes with disrupted circumnutation and long, thin-walled G-fibers. In contrast, inhibitor treatment produced short internodes with thick G-fibers. These phenotypes corresponded with significant differential expression of XTH genes, both at the onset of elongation and later, during G-layer deposition. Detection of xyloglucan epitopes in the G-layer, along with in situ hybridization, confirmed active xyloglucan remodeling after twining. C_LIO_LIOur results confirm the presence of xyloglucan in the G-layer of common bean, underscoring its importance in G-fiber function, and suggests a regulatory role for XTH genes in shaping the twining growth habit through modulation of cell wall properties. C_LI

plant 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

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↗

bioRxiv2023

Urbanisation generates multiple trait syndromes for terrestrial taxa worldwide

Cities can host significant biological diversity. Yet, urbanisation leads to the loss of habitats and, potentially, to local extinctions. Understanding how multiple taxa respond to urbanisation globally is essential to promote and conserve biodiversity in cities and surrounding landscapes. Using a dataset with site-level occurrence and trait data of 5302 species from six terrestrial fauna taxonomic groups across 379 cities on 6 continents, we show that urbanisation produces taxon-specific changes in trait composition, with traits related to reproductive strategy consistently showing the strongest response. The effect of urbanisation on community trait composition is strongest at the largest spatial scale considered, and more closely linked to landscape composition (% urban) than arrangement (aggregation), although latitude and climatic variables remain a stronger influence. This study did not find evidence in support of a global urban taxa syndrome, but instead we suggest that there are four general urban trait syndromes, with resources associated with reproduction and diet likely to be driving patterns in traits associated with mobility and body size. Functional diversity measures showed a wide range of responses, leading to a shift in trait space that is most likely driven by the distribution and abundance of critical resources, and the urban trait syndrome displayed by individual species within a community. Further research is required to understand the interactions between the four general urban trait syndromes, resource distribution and abundance and changes in functional diversity of taxa at different spatial and temporal scales. Maximising opportunities to support species within taxa groups with different urban trait syndromes should be pivotal in conservation and management programmes within and among cities. This will reduce the likelihood of biotic homogenisation at the taxa level, and helps ensure that urban environments have the ecological capacity to respond to challenges such as climate change, further habitat fragmentation and loss, and other disruptions. These actions are critical if we are to reframe the role of cities in global biodiversity loss.

ecology↗