Exploring lateral root formation in the context of a 'clock and wavefront' model

描述(申请人提供)：周期性结构是在不同的生物系统发育过程中形成的。这项建议的主要目的是在脊椎动物体节周期性形成的时钟和波前模型所建立的框架内，研究植物侧根的周期性形成。体细胞发生的模型提出，运动的分子振荡器，即分段时钟，设定体节形成的周期。时钟信号通过与波前的两个相反的信号梯度相互作用而被转换成周期段的空间模式，这是细胞响应时钟信号而变得有能力形成体节的地方。这种“时钟和波前”的机制解释了沿着脊椎动物轴线周期性连续形成体节的原因。在根中也发现了一种流动的分子振荡器，破坏它会改变LR的形成。此外，根中已经预测到一种激素梯度，我们有证据表明存在第二种梯度。我们认为“时钟和波前”机制可能是在不同的多细胞真核生物中形成周期结构的一种常见的调控策略。为了验证我们的假设，即在LR的发育过程中运行着一种“时钟和波前”机制，将解决三个具体目标。将检查振荡的行为并对其进行数学建模。将检验类维A酸类梯度在根部运行的假设，并检验该梯度与振荡的相互作用。此外，LR形成中的自然变异将被用来识别参与这一过程的基因。分析LR形成中的振荡和梯度的主要方法将是对转基因植物中的荧光素酶报告者进行实时成像。在通过化学和分子生物学方法操纵梯度时，将检查振荡的响应和随后形成LR的能力。这些实验的结果将被用来对振荡的行为及其与梯度的相互作用进行数学建模。最后，通过关联研究和数量性状基因座的分析，利用LR形成过程中的自然变异来识别参与这一过程的基因。这些研究构成了一种分析LR发展的新方法，并将揭示LR周期性如何建立和维持的根本问题。

DESCRIPTION (provided by applicant): Periodic structures are formed during development in diverse biological systems. The main objective of this proposal is to examine the periodic formation of lateral roots (LRs) in plants, within the framework established by the 'clock-and-wavefront' model for the periodic formation of somites in vertebrates. The model for somitogenesis proposes that a traveling molecular oscillator, the segmentation clock, sets the period of somite formation. The clock signal is translated into a spatial pattern of periodic segments by interaction with two opposing signaling gradients at the 'wavefront', which is where cells become competent to form somites in response to the clock signal. This 'clock-and-wavefront' mechanism accounts for the periodic serial formation of somites along the vertebrate axis. A traveling molecular oscillator has also been identified in roots and disruption of it alters LR formation. Moreover, one hormone gradient is already predicted in the root and we have evidence implicating a second gradient. We propose that the 'clock-and-wavefront' mechanism may be a common regulatory strategy in the formation of periodic structures in diverse multicellular eukaryotes. To test our hypothesis that a 'clock-and-wavefront' mechanism is operating in LR development, three specific aims will be addressed. The behavior of the oscillation will be examined and mathematically modeled. The hypothesis that a retinoid gradient operates in the root will be tested and the interaction of the gradient with the oscillation will be examined. Additionally, natural variation in LR formation will be used to identify genes involved in this process. The primary method in analyzing the oscillation and the gradient in LR formation will be real-time imaging of luciferase reporters in transgenic plants. The response of the oscillation and subsequent competency to form a LR will be examined upon manipulation of the gradients by chemical and molecular biological methods. The results of these experiments will be used to mathematically model the behavior of the oscillation and its interaction with the gradient. Finally, natural variation in LR formation will be used to identify genes involved in this process by association studies and analysis of quantitative trait loci. These studies constitute a novel way of analyzing LR development and will reveal insight into the fundamental question of how LR periodicity is established and maintained.