V-Morph_Unravelling how the mechanical regulation of local variability shapes reproducible plant organs

日益多变的气候和作物易受病原体攻击或极端环境条件的影响，造成了农产品的重大损失。此外，农业工业和最终市场往往需要高度同质的作物。这就提出了韧性的问题：如何生产健壮而均匀的作物？在这里，我们解决了发育生物学中相应的关键问题：器官如何在面对内部和外部扰动时形成一致的大小和形状？我们已经组建了一个跨学科的团队来解决高度可变的细胞和强健的器官之间明显的二分法。以前的研究主要集中在影响器官整体大小和形状的突变体和条件上，从而发现了大量的调节因子。然而，大多数分析只考虑了平均细胞行为，忽略了局部异质性和随机变异。在这里，我们采用正交的方法：我们筛选突变与增强变异性器官的大小或形状。植物会开很多花，这让我们能够发现单个生物体内的变异。我们选择了背面萼片，最外层的叶状花器官，因为它易于成像和显微操作：从原基到成熟器官的整个器官发生过程可以用共聚焦显微镜观察。萼片大小和形状的变异可以在单株植物中进行评估。基于我们之前的工作，我们提出组织力学和机械传感是器官变异性的关键调节因子，因为形态发生直接取决于生长的机械控制，因为机械应力在很大程度上取决于器官的大小和形状。我们将在拟南芥中测试这一假设，选择遗传和分子资源的可用性。我们的主要目标是(i)分析所有尺度上萼片形态发生的时空变异性，考虑到生长及其影响因素；（ii）通过对影响细胞壁、植物液压和机械传感的突变体进行定向筛选，识别和表征调节变异性的基因；（iii）将相应的机制整合到生长的机械模型中，并对这些模型进行实验测试。特别是局部机械和遗传扰动的萼片。总的来说，我们的项目解决了发育生物学中的一个核心问题，与粮食安全有关，特别是在气候波动加剧的背景下。一方面，我们将分离和表征花器官健壮性的分子调节因子。我们将在植物品系中过表达这些调节因子，并检查这些品系是否具有更多同质器官（例如同质硅藻）。另一方面，我们将在植物科学的背景下发展生物物理测量，这可能适用于广泛的研发问题，从水果硬度到生物材料特性或生物力学弹性。

Significant loss in agricultural products is caused by increasingly variable climate and vulnerability of crops to pathogen attacks or extreme environmental conditions. In addition, the agro-industry and the final market often require highly homogeneous crops. This raises the issue of resilience: How to produce robust and homogeneous crops? Here we address the corresponding key question in developmental biology: How do organs form with consistent sizes and shapes in the face of internal and external perturbations? We have assembled an interdisciplinary team to resolve the apparent dichotomy between highly variable cells and robust organs.Previous research has focused on mutants and conditions that affect the global size and shape of organs, enabling the discovery of a large number of regulators. However, most analyses have considered only average cell behaviours, overlooking local heterogeneity and stochastic variation. Here we adopt an orthogonal approach: We screen for mutants with enhanced variability in organ size or shape. Plants produce many flowers, allowing us to detect variability within an individual organism. We have chosen the abaxial sepal, the outermost leaf-like floral organ, for its accessibility for imaging and micromanipulation: the whole process of organogenesis from a primordium to the mature organ can be observed with a confocal microscope. Variability of sepal size and shape can be assessed within an individual plant.Based on our previous work, we propose that tissue mechanics and mechanosensing are key regulators of organ variability, because morphogenesis directly depends on the mechanical control of growth and because mechanical stress is largely prescribed by organ size and shape. We will test this hypothesis in Arabidopsis thaliana, chosen for the availability of genetic and molecular resources. Our main objectives are (i) to analyse spatial and temporal variability in sepal morphogenesis at all scales, considering growth and its effectors, (ii) to identify and characterise genes that regulate variability, by performing a directed screen among mutants affecting the cell wall, plant hydraulics, and mechanosensing, and (iii) to integrate the corresponding mechanisms in mechanical models of growth and test these models experimentally, notably by local mechanical and genetic perturbations to sepals.Overall, our project addresses a central question in developmental biology and is relevant to food security, especially in the context of increasing climatic fluctuations. On the one hand, we will isolate and characterise molecular regulators of the robustness of flower organs. We will overexpress these regulators in plant lines and examine if these lines have more homogeneous organs (e.g. homogenous siliques). On the other hand, we will develop biophysical measurements in the context of plant sciences, which may apply to a broad range of R&D problems, from fruit firmness to biomaterial properties or biomechanical resilience.