Making a seed pod that can shatter: the role of mechanics in valve margin development in Brassica fruits

几个世纪以来，植物一直被培育成食物、药物和燃料的来源。育种带来的许多变化都与植物发育的最优化有关，以获得最大产量。基因编辑的最新进展具有进一步提高粮食产量的巨大潜力，但我们首先需要了解植物发育的机制基础。我们的建议将侧重于水果，这在农业中非常重要--直接作为人类和动物饮食的一部分，以及间接通过种子的生产和传播。许多农作物的果实干燥成豆荚，豆荚的种子被粉碎机制分散。经济上重要的芥菜科(十字花科)的油籽就属于这一类。拟南芥果实发育已被广泛研究。这种模式种产生一种细长的果实，由两个心皮瓣片在边缘连接到种子附着在内部的质部组成。然而，水果发育和破碎背后的细胞生长模式仍然知之甚少。在这个项目中，我们将重点对影响种子产量的一个特征--豆荚破碎的关键--瓣缘的发展进行定量分析。我们的目标是揭示瓣膜边缘发育的一般原理，并了解它们如何在十字花科不同的果实形状中进行微调。我们的具体目标将是：(1)揭示导致瓣膜边缘发展的3D细胞生长模式；(2)评估机械力在瓣膜边缘规范中的作用；(3)生成瓣膜边缘生长的力学模型。共聚焦显微镜时间推移成像结合3D图像分析、计算机模拟和遗传学将被用来追踪不同十字花科物种瓣膜边缘的起源、生长和分化。我们将测量3D细胞生长、机械性能和关键模式基因的表达，以了解物理力和遗传学如何相互作用来控制瓣膜边缘的生长和发育。利用实验数据，我们将创建一个阀门边缘的3D机械模型，以评估它们如何参与阀门边缘的规范。这个模型将有助于理解细胞力学和相邻组织排列如何控制组织几何形状和豆荚破碎阻力。这项研究将为理解决定果实几何形状和豆荚破碎的生长模式建立一个有价值的框架。最近开发的一种抗豆荚破碎油菜籽品种是一个很好的例子，说明了水果发展的基本知识如何使农业受益。我们的研究有可能确定其他影响油料作物种子留存的因素。

Plants have been bred for centuries as a source of food, medicine, and fuel. Many of the changes introduced by breeding have to do with the optimization of plant development for maximum yield. Recent advances in gene editing have a huge potential to further boost food production but we first need to understand the mechanistic basis of plant development. Our proposal will focus on fruits, which are important in agriculture - directly, as part of human and animal diets, and indirectly through the production and dispersal of seeds. The fruits of many crop plants dry into pods whose seeds are dispersed by a shattering mechanism. Oilseeds in the economically important mustard family (Brassicaceae) fall into this category. Fruit development has been extensively studied in Arabidopsis thaliana. This model species produces an elongated fruit composed of two carpel valves joined at their margins to the replum to which seeds are attached on the interior. However, cellular growth patterns underlying fruit development and shattering remain poorly understood. In this project, we will focus on the quantitative analysis of the development of the valve margins which are critical for pod shatter, a characteristic that influences seed yield. We aim to uncover general principles underlying the development of the valve margin and understand how they are fine-tuned in diverse fruit shapes in Brassicaceae. Our specific objectives will be: (1) Uncover the 3D cellular growth patterns leading to the development of valve margins; (2) Assess the role of mechanical forces in the specification of the valve margins; (3) Generate a mechanical model of the valve margin growth. Confocal microscopy time-lapse imaging combined with 3D image analysis, computer simulations and genetics will be used to trace the origin, growth, and differentiation of the valve margins in various Brassicaceae species. We will measure 3D cellular growth, mechanical properties, and the expression of key patterning genes to understand how physical forces and genetics interact to control the growth and development of the valve margin. Using experimental data, we will create a 3D mechanical model of valve margins to assess how they could be involved in the specification of valve margins. This model will be instrumental in understanding how tissue geometries and pod shatter resistance are controlled by cell mechanics and adjacent tissue arrangements. This research will establish a valuable framework for understanding patterns of growth that determine fruit geometry and pod shattering. The recent development of a pod-shatter-resistant variety of canola is an excellent example of how fundamental knowledge of fruit development has benefitted agriculture. Our research has the potential to identify other factors influencing seed retention in oilseed crops.