Building integrated models of plant growth and development.
Building integrated models of plant growth and development.
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建立植物生长和发育的综合模型。
DOI：
10.1104/pp.102.017061
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Chory,Joanne
中科院分区：
文献类型：
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作者：
Nemhauser,JenniferL;Maloof,JulinN;Chory,Joanne
系统生物学旨在破译信号网络的结构和动力学（Kitano，2002）。在这些方法的核心一个重要的未回答的问题是：简单的数学模型可以充分描述复杂过程中的信号集成？理想情况下，这样的模型存在于一个循环中，它们被用来生成新的实验假设，一旦被测试，就被用来完善模型并导致更复杂的假设。最终，这些知识可以用来深入了解给定的过程，并预测对复杂刺激的反应。开始，我们需要一个有趣的生物过程和一个可靠的定量反应测量。光形态发生在这两方面都提供了一个很好的框架。在自然界中，种子在各种光照条件下发芽。光被一套光感受器感知，包括主要吸收红光/远红光的光敏色素（Wang和Deng，2002）。在低水平的光，幼苗表现出大大延长下胚轴和小子叶紧紧包围先端。随着光照强度的增加，下胚轴的伸长速率降低，子叶扩展，茎尖分生组织启动新叶。几种激素参与促进或拮抗光反应（Nemhauser和Chory，2002）。例如，油菜素类固醇（BR）合成或感知缺陷的突变体表现出显著的光生长形态，当在黑暗中生长时光诱导转录物的上调，以及改变的光响应（Friedrichsen和Chory，2001; Luccioni等人，2002年）。几个因素与BR水平的光依赖性调节有关（Neff等人，1999; Kang等人，2001; Wang等人，2002）。作为对幼苗生长采取系统方法的第一步，我们使用下胚轴长度作为方便的定量测量，创建了光和激素响应的矩阵。四种基因型的植物（野生型，BR受体[BRI 1]的过表达，和缺乏光受体光敏色素A或B的突变体）暴露于五个通量率的红光或远红光和五个水平的外源油菜素（BL），最活跃的BR。在这些条件下观察到的野生型幼苗形态的显著范围如图1所示。对每个变量的反应如前所述（Friedrichsen和Chory，2001年; Wang和Deng，2002年）。暴露于更高的光强度，无论是红色或远红色，导致下胚轴长度减少。远红光照射对下胚轴长度的抑制作用比红光明显。BL影响幼苗生长的程度取决于幼苗所暴露的光的颜色和强度。幼苗下胚轴生长在红光下，暴露于高浓度的BL表现出“扭结”的生长习性，在较低的光通量率的效果是更显着的。红光下BL对下胚轴长度的负效应与远红光下BL对下胚轴长度的负效应不同。在低强度的远红光下，BL对下胚轴伸长只有很小的影响，而在高强度的远红光下，暴露于BL产生了下胚轴长度的大幅增加。我们想知道，通过这种不同输入因素的矩阵实现的形式多样性是否可以数学建模，如果可以的话，这种模型将揭示这种反应背后的光/激素关系。由遗传和环境因素的多维网格产生的下胚轴长度测量结果被可视化为三维表面图（图2）。如果这段关系...
Systems biology aims to decipher the structure and dynamics of signaling networks (Kitano, 2002). An important unanswered question at the heart of such approaches is: Can simple mathematical models adequately describe signal integration in complex processes? Ideally, such models exist in a cycle where they are used to generate new experimental hypotheses that, once tested, are used to refine the model and lead to more sophisticated hypotheses. Ultimately, such knowledge can be used both to gain an in-depth understanding of a given process and to predict responses to complex stimuli. To begin, one needs both an interesting biological process and a robust quantitative measure of response. Photomorphogenesis provides an excellent framework on both counts. In nature, seeds germinate in a wide range of light conditions. Light is perceived by a suite of photoreceptors, including the primarily red/far-red light-absorbing phytochromes (Wang and Deng, 2002). In low levels of light, seedlings exhibit greatly elongated hypocotyls and small cotyledons tightly enclosing the apex. As light intensity increases, the rate of hypocotyl elongation decreases, cotyledons expand, and the shoot apical meristem initiates new leaves. Several hormones have been implicated in promoting or antagonizing light responses (Nemhauser and Chory, 2002). For example, mutants defective in brassinosteroid (BR) synthesis or perception exhibit strikingly light-grown morphology, up-regulation of light-induced transcripts when grown in the dark, and altered light responses (Friedrichsen and Chory, 2001; Luccioni et al., 2002). Several factors have been linked with lightdependent regulation of BR levels (Neff et al., 1999; Kang et al., 2001; Wang et al., 2002).As a first step toward taking a systems approach to seedling growth, we created a matrix of light and hormone response, using hypocotyl length as a convenient quantitative measure. Plants of four genotypes (wild type, overexpressers of the BR receptor [BRI1], and mutants lacking photoreceptors phytochrome A or B) were exposed to five fluence rates of red or far-red light and five levels of exogenous brassinolide (BL), the most active BR. The dramatic range of wild-type seedling morphology observed under these conditions is shown in Figure 1. The response to each variable considered on its own was as described previously (Friedrichsen and Chory, 2001; Wang and Deng, 2002). Exposure to higher light intensities, whether red or far-red, resulted in reduced hypocotyl length. Illumination with far-red light caused a more dramatic inhibition of hypocotyl length than red light. The extent to which BL affected seedling growth depended upon the color and intensity of light to which the seedlings were exposed. Hypocotyls of seedlings grown in red light and exposed to high concentrations of BL exhibited a “kinked” growth habit, an effect that was more dramatic at lower fluence rates of light. This negative effect of BL on hypocotyl length observed in red light was quite different from what was observed in farred light. In low intensities of far-red light, BL had only a small effect on hypocotyl elongation, whereas in high intensities of far-red light, exposure to BL produced a substantial increase in hypocotyl length. We wanted to ask if the diversity of form achieved through such a matrix of different input factors could be modeled mathematically, and if so, what such a model would reveal about the light/hormone relationships underlying this response. Hypocotyl length measurements resulting from this multidimensional grid of genetic and environmental factors were visualized as three-dimensional surface plots (Fig. 2). If the relationship …