Biology subjects

Mollier, C.

Publications and source records attributed to Mollier, C..

3 recordsLinked to original sources

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↗

bioRxiv2022

Spatial consistency of cell growth direction during organ morphogenesis requires CELLULOSE-SYNTHASE INTERACTIVE1

Extracellular matrices generally contain fibril-like polymers that may be organized in parallel arrays. Although their role in morphogenesis has been long recognized, it is still unclear how the subcellular control of fibril synthesis translates into well-defined organ shape. Here, we addressed this question using the Arabidopsis sepal as a model organ. In plants, cell growth is driven by turgor pressure and restrained by the extracellular matrix known as the cell wall. Cellulose is the main load-bearing component of the plant cell wall and cellulose microfibrils are thought to channel growth perpendicularly to their main orientation. Given the key function of CELLULOSE SYNTHASE INTERACTIVE 1 (CSI1) in guidance of cellulose synthesis, we investigated the role of CSI1 in sepal morphogenesis. We observed that sepals from csi1 mutants are shorter, although their newest cellulose microfibrils are more aligned compared to wild type. Surprisingly, cell growth anisotropy was similar in csi1 and wild-type plants. We resolved this apparent paradox using polarized Raman microspectroscopy, live imaging of growing sepals, and bespoke mechanical assays. We found that CSI1 is required for spatial consistency of growth direction across the sepal and for the maintenance of overall organ elongation. Our work illustrates how the subcellular regulation of the extracellular matrix may control morphogenesis at multiple scales.

developmental biology↗

bioRxiv2022

Robustness of organ morphology is associated with modules of co-expressed genes related to plant cell wall

Control of organ morphology is a fundamental feature of living organisms. There is, however, observable variation in organ size and shape within a given genotype. Taking the sepal of Arabidopsis as a model, we investigated whether we can use variability of gene expression alongside variability of organ morphology to identify gene regulatory networks potentially involved in organ size and shape determination. We produced a dataset composed of morphological parameters and genome-wide transcriptome obtained from 27 individual sepals from wild-type plants with nearly identical genetic backgrounds, environment, and developmental stage. Sepals exhibited appreciable variability in both morphology and transcriptome, with response to stimulus genes and cell-wall related genes displaying high variability in expression. We additionally identified five modules of co-expressed genes which correlated significantly with morphology, revealing biologically relevant gene regulatory networks. Interestingly, cell-wall related genes were overrepresented in two of the top three modules. Overall, our work highlights the benefit of using coupled variation in gene expression and phenotype in wild-type plants to shed light on the mechanisms underlying organ size and shape determination. Although causality between gene expression and sepal morphology has not been established, our approach opens the way to informed analysis for mutant characterization and functional studies.

plant biology↗