Biology subjects

Malivert, A.

Publications and source records attributed to Malivert, A..

4 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↗

bioRxiv2023

Sugar signaling modulates SHOOT MERISTEMLESS expression and meristem function in Arabidopsis

In plants, development of all above-ground tissues is controlled by the shoot apical meristem (SAM) which balances cell proliferation and differentiation to allow life-long growth. To maximize fitness and survival, meristem activity is adjusted to the prevailing conditions through a poorly understood integration of developmental signals with environmental and nutritional information. Here, we show that sugar signals influence SAM function by altering the protein levels of SHOOT MERISTEMLESS (STM), a key regulator of meristem maintenance. STM is less abundant in the inflorescence meristems of plants grown or treated under limiting light conditions, with lower STM levels correlating with lower sugar content in these meristems. Additionally, sucrose but not light is sufficient to sustain STM accumulation in excised inflorescences. Plants overexpressing the 1-subunit of SUCROSE-NON-FERMENTING1-RELATED KINASE 1 (SnRK1) accumulate less STM protein under optimal light conditions, despite higher sugar accumulation in the meristem. Furthermore, SnRK11 interacts physically with STM, suggesting a direct local repression. Surprisingly, silencing SnRK1 in the meristem leads to reduced STM expression and severe developmental phenotypes previously associated with STM loss-of-function. Altogether, we demonstrate that sugars promote STM accumulation and that the SnRK1 sugar sensor plays a dual role in the SAM, limiting STM abundance under unfavorable conditions but being required for overall meristem organization and integrity. This highlights the importance of sugars and SnRK1 signaling for the proper coordination of meristem activities.

plant biology↗

bioRxiv2021

Turning plants from passive to active material: FERONIA and microtubules independently contribute to mechanical feedback

To survive, cells must constantly resist mechanical stress. In plants, this involves the reinforcement of cell walls, notably through microtubule-dependent cellulose deposition, and thus wall sensing. Several receptor-like kinases have been proposed to act as mechanosensors. Here we tested whether the microtubule response to stress acts downstream of known wall sensors. Using a multi-step screen with eleven mutant lines, we identify FERONIA as the primary candidate for controlling the microtubule response to stress. However, when performing mechanical perturbations, we show that the microtubule response to stress can be independent from FER. We reveal that the feronia phenotype can be partially rescued by reducing tensile stress levels. Conversely, in the absence of both microtubules and FER, cells swell and burst like soap bubbles. Altogether, this shows that the microtubule response to stress acts as an independent pathway to resist stress, in parallel to FER. We propose that both pathways are key components to turn plant cells from passive to active material.

plant biology↗

bioRxiv2017

Nitrate modulates stem cell dynamics by regulating WUSCHEL expression through cytokinins

The shoot apical meristem (SAM) is responsible for the generation of all of the aerial parts of plants1. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment2. Using quantitative microscopy, grafting experiments and genetic perturbations, we connect the plant environment to the SAM, by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show that a systemic signal of cytokinin precursors3 mediates the adaptation of SAM size and organogenesis rate to the availability of mineral nutrients by modulating the expression of WUSCHEL, a key regulator of stem cell homeostasis4. In time-lapse experiments, we further show that this mechanism allows meristems to adapt to rapid changes in nitrate concentration, and thereby modulate their rate of organ production to the availability of mineral nutrients within a few days. Our work sheds new light on the role of the stem cell regulatory network, by showing that it does not only maintain meristem homeostasis but also allows plants to adapt to rapid changes in the environment.

plant biology↗