Biology subjects

Willoughby, A. C.

Publications and source records attributed to Willoughby, A. C..

3 recordsLinked to original sources

bioRxiv2025

Gene duplication dynamics and regulatory evolution shape the diversification of Asteraceae

The flowering plant order Asterales exhibits a striking disparity in species richness, with >30,000 species in Asteraceae compared to <50 in its sister family Calyceraceae. To investigate the genomic basis of this imbalance, we assembled three new chromosome-level genomes, including the first for Calyceraceae, and re-annotated five additional genomes. Comparative analyses revealed exceptionally high repeat content in both Asteraceae and Calyceraceae, pervasive chromosomal rearrangements, and evidence for shared and lineage-specific WGDs. In Asteraceae, tandem and dispersed duplications disproportionately drove expansions of gene families linked to secondary metabolism and stress response, while segmental duplicates bore signatures of adaptive selection for the regulation of biosynthetic and metabolic processes. Selective pressures on flowering time regulators suggest an evolved balance between regulatory flexibility and developmental constraint in floral diversification. These patterns reveal that, beyond ancient polyploidy, small-scale duplications and selective fine-tuning of regulatory networks underpinned the ecological versatility in Asteraceae, fueling its extraordinary diversification.

genomics↗

bioRxiv2025

Floral innovation through modifications in stem cell peptide signaling.

Understanding how evolution shapes genetic networks to create new developmental forms is a central question in biology. Asteraceae (sunflower family) comprise 10% of flowering plants and have capitula, a novel flowering shoot (inflorescence) that mimics a single flower (1, 2). During capitulum development, shoot stem cells undergo prolonged proliferation relative to other species (3, 4). Here we show that capitulum evolution paralleled decreases in CLAVATA3 peptide (CLV3p) signaling, a conserved repressor of stem cell proliferation. Asteraceae CLV3p displays reduced receptor binding and downstream transcriptional outputs. Reversion of CLV3 to a more active form impairs Asteraceae stem cell regulation and capitulum development. Lastly, we trace CLV3 evolution across the Asterales allowing inferences on capitulum evolution. Our findings reveal novel evolutionary mechanisms in plant reproduction and suggest approaches for engineering crops.

plant biology↗

bioRxiv2025

Canalization of flower production across thermal environments requires Florigen and CLAVATA signaling.

The ability to maintain invariant developmental phenotypes across disparate environments is termed canalization, but few examples of canalization mechanisms are described. In plants, robust flower production across environmental gradients contributes to reproductive success and agricultural yields. Flowers are produced by the shoot apical meristem (SAM) in an auxin-dependent manner following the switch from vegetative growth to the reproductive phase. While the timing of this phase change, called the floral transition, is sensitized to numerous environmental and endogenous signals, flower formation itself is remarkably invariant across environmental conditions. Previously we found that CLAVATA peptide signaling promotes auxin-dependent flower primordia formation in cool environments, but that high temperatures can restore primordia formation through unknown mechanisms. Here, we show that heat promotes floral primordia patterning and formation in SAMs not by increased auxin production, but through the production of the mobile flowering signal, florigen, in leaves. Florigen, which includes FLOWERING LOCUS T (FT) and its paralog TWIN SISTER OF FT (TSF) in Arabidopsis thaliana, is necessary and sufficient to buffer flower production against the loss of CLAVATA signaling and promotes heat-mediated primordia formation through specific SAM expressed transcriptional regulators. We find that sustained florigen production is necessary for continuous flower primordia production at warmer temperatures, contrasting florigens switch-like control of floral transition. Lastly, we show that CLAVATA signaling and florigen synergize to canalize flower production across broad temperature ranges. This work sheds light on the mechanisms governing the canalization of plant development and provides potential targets for engineering crop plants with improved thermal tolerances.

plant biology↗