PIN proteins and architectural change in plants.

生物学的一个关键挑战是了解具有复杂形状和特殊功能的身体部位在发育过程中是如何出现的。在植物中，整体形状反映了分枝的模式，叶片起始的模式和叶片从顶端开始的相对生长。这些性状强烈影响植物生产力，因为它们影响光合作用中的光截获。由于许多作物品种是几乎没有分枝的草，叶子的形状和它们在茎周围的排列特别重要。由于这些原因，科学家对了解调节叶片排列和生长的基本机制非常感兴趣。为了研究这个问题，我们正在研究一种苔藓（小立碗藓），它像许多植物一样，有围绕茎螺旋状排列的叶子。立碗藓作为叶片发育的模型具有许多优势。苔藓是一个进化古老的群体，其中大多数在其他植物中起作用的基因家族都由较少的家族成员代表，这使得精确定位基因功能变得更加简单。植株非常小，茎尖由单个细胞组成。叶起始为单细胞，并且是单细胞层厚。这意味着我们已经能够开发出一种技术，用于在显微镜下拍摄芽启动，叶启动和叶发育，并可以生成有关细胞分裂和生长如何影响整体植物形状的定量信息。如果没有计算输入，分析和解释这些数据是困难的，因此我们正在与计算机科学家合作，以确定形状的关键贡献者。这样的计算分析到目前为止抽象叶发育的组织规模，或集中在一个特定的方面的发展，以尽量减少计算机处理的限制。由于苔藓叶片细胞较少，我们已经能够建立一个叶片发育的细胞模型，该模型对细胞分裂和生长对最终叶片形状的贡献做出了具体的预测。植物激素生长素在调节番茄和拟南芥等植物的叶片起始模式和叶片形状方面起着主要作用，因为它调节细胞身份和生长的决定。生长素的分布是其活性的一个重要方面，其转运受一个小基因家族的载体蛋白的影响。目前用于评估载体蛋白如何影响生长素分布和对整体形状的影响的方法受到多个基因家族成员对运输的贡献的限制。监测开花植物叶片中的生长素分布也具有挑战性，因为它只能通过监测生长素响应基因的活性变化间接实现，并且开花植物叶片具有复杂的组织组成，这限制了显微镜下的组织渗透。苔藓枝条的解剖学和遗传学的简单性再次带来了挑战。利用苔藓来了解植物形状是如何获得的另一个优势是，苔藓枝条对大多数枝条系统都有独立的进化起源。这意味着，如果调节形状的机制与其他更好研究的群体（如显花植物）共享，它们可能是植物形状的通用调节器。因此，我们创造的知识将具有非常广泛的适用性。

A key challenge in biology is to understand how body parts with complex shapes and specialized functions arise during development. In plants, the overall shape reflects the pattern of branching, the pattern of leaf initiation and the relative growth of leaves initiated from the tip. These traits impact strongly on plant productivity because they affect light interception in photosynthesis. Because many crop species are grasses that have little branching, the shape of leaves and their arrangement around the stem are particularly important. For these reasons, understanding the basic mechanisms that regulate leaf arrangements and growth is of considerable interest to scientists. To study this problem, we are working on a moss (Physcomitrella patens), which like many plants, has leaves that are arranged in a spiral pattern around the stem. Physcomitrella has many advantages as a model for leaf development. Mosses are an evolutionary ancient group in which most gene families functioning in other plants are represented by fewer family members, making it simpler to pinpoint gene function. The plants are very small and the shoot apex is made up of a single cell. Leaves initiate as a single cell and are a single cell layer thick. This means that we have been able to develop a technique for filming shoot initiation, leaf initiation and leaf development microscopically, and can generate quantitative information about how cell division and growth contribute to overall plant shape. Analysis and interpretation of this data is difficult without computational input, so we are working with computer scientists to identify key contributors to shape. Such computational analyses have so far abstracted leaf development to the tissue scale, or focussed on a specific aspect of development to minimise computer processing constraints. Because moss leaves have few cells, we have been able to generate a cellular model of leaf development that has made specific predictions about the contribution of cell division and growth to final leaf shape.A plant hormone, auxin, plays a primary role in modulating leaf initiation patterns and leaf shape in plants like tomato and Arabidopsis as it regulates decisions about cell identity and growth. The regulated distribution of auxin is a key aspect of its activity, and transport is effected by carrier proteins belonging to a small gene family. Current approaches for evaluating how the carrier proteins effect the auxin distribution and impact on overall shape are limited by the contribution of multiple gene family members to transport. Monitoring the auxin distribution in flowering plant leaves has also been challenging as it can only be achieved indirectly by monitoring changes in the activity of auxin responsive genes, and flowering plant leaves have a complex tissue composition that limits tissue penetration in microscopy. The anatomical and genetic simplicity of the moss shoot again brings an advantage.A further advantage in using moss to understand how plant shape is attained is that moss shoots have an independent evolutionary origin to most shoot systems. This means that if the mechanisms regulating shape are shared with other better studied groups like flowering plants, they are likely to be universal regulators of plant shape. The knowledge that we genenerate will therefore be very broadly applicable.