Bilateral NSF/BIO-BBSRC: Unravelling the Grass Leaf

开花植物表现出两种主要的生长策略。双子叶植物的生长策略是植物的生长顶端通过在其下方产生伸长的茎而向上攀爬。叶芽也在生长顶端产生，最终从茎中生长出来形成完全生长的叶子。单子叶植物的策略是让生长的顶端在植物的基部受到保护，并产生一系列同心的叶子，这些叶子在上面升起。叶片出现并在同心圆柱体或叶基部的顶部向外弯曲。只有在后期，生长尖本身才通过茎的伸长而向上升起，以产生开花结构。这种单子叶植物策略的优点是在植物的大部分生活史中保护植物基部的生长尖端。它使牧草能够在大面积放牧中生存下来，是小麦、玉米和水稻等谷物的生长策略。尽管单子叶植物策略在生态和农学上具有重要意义，但人们对单子叶植物策略的了解远不如双子叶植物策略。特别是，目前还不清楚单子叶植物叶芽如何生长形成同心圆柱体，顶部向外弯曲的叶片。通过使用计算模型，我们已经开发了一些初步的假设，这可能是如何工作的。一个关键的想法是，生长是由极性场定向的;类似于磁场可以用来定向导航方向的方式。观察到的单子叶植物叶的生长和形状变化，然后可以解释为简单的变化，极性场和模式的增长率，它的方向。本提案的主要目的是测试和进一步建立在这个模型，以确定它预测的领域和增长率是否正确。这将通过使用玉米单子叶系统来实现，该系统具有良好的遗传学和相关技术的优势。通过观察突出假定极性场的标记并确定叶片不同区域的生长速率，我们希望测试模型的预测。还将通过分析发育的关键过渡被破坏的突变体来测试模型。这些研究将通过编写自动提取相关测量值的计算机程序进行定量。新的计算方法也将被开发并应用于这一系统，以便从细胞到组织的不同层次上理解这一过程。这种类型的研究，将计算和实验方法相结合，应该为单子叶植物生长策略背后的奥秘提供严格和定量的理解。它产生的理解也可能使我们能够进一步调节作物叶片的形状和配置。例如，叶片向外弯曲的角度取决于叶片连接处的生长，并且对产量有重要影响，因为它影响可以用于光合作用的光量。因此，了解这一过程是如何运作的，以及基因是如何控制的，可能有助于育种者提高作物的表现。

Flowering plants exhibit two major growth strategies. The dicot strategy is for the growing tip of the plant to climb upward by producing an elongating stem below it. Leaf buds are also generated at the growing tip and eventually these grow out from the stem to form fully grown leaves. The monocot strategy is for the growing tip to stay protected at the base of the plant and produce a series of concentric leaves that rise above it. Leaf blades emerge and bend outwards at the top of the concentric cylinder or leaf bases. Only at later stages does the growing tip itself rise upwards through elongation of the stem to produce the flowering structures. This monocot strategy has the advantage of protecting the growing tip at the base of the plant for much of its life history. It enables grasses to survive extensive grazing and is the growth strategy that underlies cereals like wheat, maize and rice.Despite its ecological and agronomic importance, the monocot strategy is much less well understood than the dicot strategy. In particular, it is unclear how monocot leaf buds grow to form concentric cylinders topped by outwardly bending blades. By using computational modelling we have developed some preliminary hypotheses for how this might work. A key idea is that growth is oriented by a polarity field; analogous to the way a magnetic field can be used to orient directions of navigation. The observed growth and shape changes of the monocot leaf can then be explained by simple changes in the polarity field and pattern of growth rates it orients. The main aim of this proposal is to test and further build upon this model to determine whether the fields and rates of growth it predicts are correct or not. This will be achieved using the maize monocot system which has the advantage of having well developed genetics and associated technologies. By looking at markers that highlight the presumed polarity fields and determining the growth rates in different regions of the leaf we hope to test predictions of the model. Models will also be tested by analysing the mutants in which key transitions of development are disrupted. These studies will be made quantitative by writing computer programs that extract the relevant measures automatically. New computational methods will also be developed and applied to this system so that the processes can be understood at different levels, from cellular to tissue scale.This type of study, which integrates computational and experimental approaches, should provide a rigorous and quantitative understanding of the mysteries behind the monocot growth strategy. The understanding it generates may also allow us to further modulate the shape and disposition of leaves in crops. The angle at which the leaf blade bends out, for example, depends on growth at the blade junction, and has an important effect on yield because it influences the amount of light that can be harvested for photosynthesis. Knowing how this process works and is controlled by genes may therefore help breeders improve crop performance.