The chemical dynamics of organ positioning in conifer development

针叶树发育中器官定位的化学动力学

• 批准号: RGPIN-2016-04857
• 负责人: Holloway, David
• 金额: $ 1.09万
• 依托单位: British Columbia Institute of Technology
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=675673
• 关键词: chemical; dynamics; organ; positioning; conifer

While math has long been used to describe plant patterns (e.g. the Fibonacci numbers observed in lateral organ arrangements, such as in pine cones), recent developments in molecular imaging have spurred a growing recognition in biology that many aspects of plant development are inherently quantitative (such as organ spacing, plant shape and architecture) and require mathematical theory to explain the underlying molecular mechanisms. Much of the new quantitative and mathematical work has been on the spatial distribution of the hormone auxin (a primary determinant of local growth) in the model plant Arabidopsis.***Our work focuses on the unique dynamical aspects of developmental patterning and growth in conifer morphogenesis. Arabidopsis has two cotyledons (seed leaves'), which form in a planar arrangement; conifers have a variable number (frequently from 2 to 12), which form in a whorl on a domed geometry. Conifer cotyledons can therefore have much more complex spatial patterning (i.e. higher-order modes for growth catalyst patterns; more complex pattern selection to produce whorled morphogenesis). We have used reaction-diffusion (RD) models to characterize concentration patterning on surfaces in 3D which, coupled to local growth, represent the symmetry-breaking mechanism positioning the conifer whorls. We have studied the geometric dependence of patterning on experimentally-observed dome flattening, as well as expanding earlier theoretical ideas that whorled structures on domed geometries form in two stages a 1st stage to position the whorl, a 2nd stage to subdivide the whorl into cotyledons. Experimentally, we have found two such stages in spruce, and that they are separable by disruption of auxin transport. ***We now plan to incorporate the unique up-the-gradient' polar auxin transport (PAT) dynamics (discovered in Arabidopsis) into our 3D model. This addresses conifer geometry and local growth (which are not contained in any of the Arabidopsis models), and will also produce a new, continuous formulation of PAT (prior models are cell-based and discrete). Finite-element computations and mathematical analysis will be used to find the relative contributions of RD and PAT (on a growing domain) in conifer cotyledon formation (including dependence on particular reaction nonlinearities). Model dynamics will be refined by new 3D experimental data on auxin distributions. ***Benefits to field: advancing new mathematical techniques in plant science; training interdisciplinary scientists; leveraging recent large molecular and modelling efforts in Arabidopsis to understand conifers. Benefits to Canada: supporting Canadian expertise in mathematical, quantitative biology to gain quantitative understanding and control of the development of conifers, which are of central value to the country's ecology and economy (forestry is $20B of GDP, nearly 80% of forest tree species are conifers).*****************

虽然数学长期以来一直被用来描述植物模式（例如在横向器官排列中观察到的斐波那契数，如在松果中），但分子成像的最新发展促使生物学越来越认识到植物发育的许多方面本质上是定量的（如器官间距，植物形状和结构），需要数学理论来解释潜在的分子机制。许多新的定量和数学工作都是关于模式植物拟南芥中激素生长素（局部生长的主要决定因素）的空间分布。我们的工作集中在针叶树形态发生中发育模式和生长的独特动力学方面。拟南芥有两片子叶（种子叶），形成平面排列;针叶树有可变的数量（通常从2到12），形成圆顶几何形状上的螺旋。因此，针叶树子叶可以有更复杂的空间模式（即生长催化剂模式的高阶模式;更复杂的模式选择，以产生轮生形态发生）。我们已经使用了反应扩散（RD）模型来表征浓度图案化的表面在3D中，再加上当地的增长，代表的针叶树轮定位的破胶机制。我们已经研究了实验观察到的圆顶扁平化的图案的几何依赖性，以及扩展早期的理论思想，即圆顶几何形状上的螺纹结构形成两个阶段：第一阶段定位螺纹，第二阶段将螺纹细分为子叶。实验上，我们在云杉中发现了两个这样的阶段，并且它们可以通过破坏生长素运输来分离。* 我们现在计划将独特的“梯度向上”极性生长素运输（PAT）动力学（在拟南芥中发现）纳入我们的3D模型。这解决了针叶树的几何形状和局部生长（这是不包含在任何拟南芥模型），也将产生一个新的，连续的配方PAT（以前的模型是基于细胞和离散）。将使用有限元计算和数学分析来找到RD和PAT（在生长域）在针叶树子叶形成（包括依赖于特定的反应非线性）的相对贡献。模型动力学将通过生长素分布的新的3D实验数据进行改进。*** 对外地的好处：在植物科学中推进新的数学技术;培训跨学科科学家;利用最近在拟南芥中的大型分子和建模工作来了解针叶树。对加拿大的好处：支持加拿大在数学，定量生物学方面的专业知识，以获得对针叶树发展的定量理解和控制，这对该国的生态和经济具有核心价值（林业占GDP的200亿美元，近80%的森林树种是针叶树）。