Biology subjects

Runions, A.

Publications and source records attributed to Runions, A..

3 recordsLinked to original sources

bioRxiv2024

Age-associated growth control modifies leaf proximodistal symmetry and enables leaf shape diversification

Biological shape diversity is often manifested in modulation of organ symmetry and modification of the patterned elaboration of repeated shape elements.1-5 Whether and how these two aspects of shape determination are coordinately regulated is unclear.5-7 Plant leaves provide an attractive system to investigate this problem, because they usually show asymmetries along their proximodistal axis, along which they can also produce repeated marginal outgrowths such as serrations or leaflets.1 One case of leaf shape diversity is heteroblasty, where the leaf form in a single genotype is modified with progressive plant age.8-11 In Arabidopsis thaliana, a plant with simple leaves, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) controls heteroblasty by activating CyclinD3 expression, thereby sustaining proliferative growth and retarding differentiation in adult leaves.12 However, the precise significance of SPL9 action for leaf symmetry and marginal patterning is unknown. By combining genetics, quantitative shape analyses, and time-lapse imaging, we show that, in A. thaliana, proximodistal symmetry of the leaf blade decreases in response to an age-dependent SPL9 expression gradient, and that SPL9 action coordinately regulates the distribution and shape of marginal serrations and overall leaf form. Using comparative analyses, we demonstrate that heteroblastic growth reprogramming in Cardamine hirsuta, a complex-leafed relative of A. thaliana, also involves prolonging the duration of cell proliferation and delaying differentiation. We further provide evidence that SPL9 enables species-specific action of homeobox genes that promote leaf complexity. In conclusion, we identify an age-dependent layer of organ proximodistal growth regulation that modulates leaf symmetry and has enabled leaf shape diversification. In BriefAge-dependent regulation of proliferative growth and differentiation along the proximodistal axis of leaves modulates organ symmetry and marginal patterning in heteroblasty, and enabled the action of homeobox genes in complex leaf shape evolution. HighlightsO_LIAn age-dependent growth gradient underpins regulation of A. thaliana leaf symmetry C_LIO_LISPL9-mediated heteroblastic growth control potentiates leaf histogenic capacity C_LIO_LIA common growth framework underlies heteroblasty in complex and simple leaves C_LIO_LISPL9 enables the action of homeobox genes that promote leaf complexity C_LI

developmental biology↗

bioRxiv2023

Puzzle cell shape emerges from the interaction of growth with mechanical constraints

Puzzle-shaped epidermal cells not only reduce mechanical stress during organ growth but also record the expansion history of the tissue in their outlines. By combining mechanical simulations with time-lapse imaging, we show that transitions from directional to isotropic expansion induce new lobes to form along the previous growth axis, and that switching the order of anisotropic and isotropic phases yields hybrid shapes that reliably preserve those transitions. In maize, model predictions and live imaging coincide precisely, and in Ara-bidopsis, final lobe patterns correlate more with growth history than with cell size alone. Ge-netic or pharmacological disruption of lobe formation constrains leaf expansion or drives compensatory elongation, which underscores a mechanical function. A broad survey of living and fossil vascular plants reveals that the mechanism to make puzzle-shaped cells is both widespread and developmentally plastic, suggesting that single snapshots of leaves can give insight into their growth history. Together, these findings demonstrate that puzzle cells trans-form cell geometry into a living record of how tissues grow.

plant biology↗

bioRxiv2021

MorphoGraphX 2.0: Providing context for biological image analysis with positional information

Positional information is a central concept in developmental biology. In developing organs, positional information can be idealized as a local coordinate system that arises from morphogen gradients controlled by organizers at key locations. This offers a plausible mechanism for the integration of the molecular networks operating in individual cells into the spatially-coordinated multicellular responses necessary for the organization of emergent forms. Understanding how positional cues guide morphogenesis requires the quantification of gene expression and growth dynamics in the context of their underlying coordinate systems. Here we present recent advances in the MorphoGraphX software (Barbier de Reuille et al. eLife 2015;4:e05864) that implement a generalized framework to annotate developing organs with local coordinate systems. These coordinate systems introduce an organ-centric spatial context to microscopy data, allowing gene expression and growth to be quantified and compared in the context of the positional information thought to control them.

developmental biology↗