Regulation of root growth under osmotic stress conditions: a systems study

为不断增长的全球人口增加粮食安全是人类面临的一项重大挑战。根系结构的调节是植物对干旱反应的一个关键特征，可能导致产量效益。因此，了解干旱条件下根系发育的调节机制是植物生物学和世界农业的一个重要问题。先前，通过结合分子生物学（我们的实验数据和文献数据）和系统生物学（网络构建和时空建模），我们构建了一个描述生长素、乙烯、细胞分裂素和POLARIS肽（拟南芥中正确的生长素、乙烯和细胞分裂素信号传导所必需的）之间相互作用的网络，揭示了调节根生长的激素串扰电路。该模型已扩展到包括生长素通过PIN- formed （PIN）外排转运体的运输，并已实现到一个时空模型中，该模型可以再现各种激素和反应基因的模式。此外，我们还研究了渗透胁迫对ABA、细胞分裂素和乙烯反应的影响，以及它们如何通过影响PIN蛋白介导生长素的运输、分布和根生长。我们发现，在渗透胁迫下，拟南芥植物表现出增加的ABA反应，并通过改变PIN1水平证明了生长素转运到初生根分生组织的影响。然后，我们利用这些信息构建了一个新的网络，将渗透胁迫和ABA与生长素、乙烯和细胞分裂素的影响整合在一起。这一网络为ABA抑制乙烯效应从而限制生长素在分生组织中的积累而形成ABA、生长素、乙烯和细胞分裂素的整合系统提供了新的见解，并为渗透胁迫下根系发育的控制提供了新的认识。目前的项目建立在我们成功应用分子生物学和系统生物学相结合的研究基础上，进一步探索渗透胁迫条件下根系发育的调控。该项目关注的问题是“渗透胁迫如何调节根分生组织的大小”。它将提供广泛的分子和系统生物学领域的严格培训。它将培养分子生物学和系统生物学的技能。这包括以下全部或部分技能：RNA提取和cDNA合成；实时定量聚合酶链反应（qPCR）；复合光学显微镜；共聚焦激光扫描显微镜；活体成像系统；图像分析;网络建设;计算机软件;以及各种建模技术。本项目的一个重要特点是采用分子生物学和系统生物学相结合的研究方法来探索渗透胁迫下根系生长调控的复杂性。

Increasing food security for a growing global population is a major challenge facing humanity. Modulation of root system architecture is a key feature of plant responses to drought, potentially leading to yield benefits. Understanding the mechanisms regulating root development under drought conditions is therefore an important question for plant biology and world agriculture.Previously, by combining molecular biology (our experimental data and the data in the literature) with systems biology (network construction and spatiotemporal modelling), we have constructed a network describing the interactions between auxin, ethylene, cytokinin and the POLARIS peptide (required for correct auxin, ethylene and cytokinin signalling in Arabidopsis), revealing a hormonal crosstalk circuit that regulates root growth. This model has been expanded to include auxin transport via the PIN-FORMED (PIN) efflux transporters and has been implemented into a spatiotemporal model, which can reproduce the patterning of various hormones and response genes. In addition, we examined the effect of osmotic stress on ABA, cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We showed that under osmotic stress, Arabidopsis plants display increased ABA responses, and demonstrated the effects on auxin transport to the primary root meristem through altered PIN1 levels. We then used this information to construct a new network to integrate the effects of osmotic stress and ABA with auxin, ethylene and cytokinin. This network developed novel insights into how an integrated system of ABA, auxin, ethylene and cytokinin is formed due to the repression of ethylene effects by ABA to limit auxin accumulation in the meristem, and brought new understanding to the control of root development under osmotic stress. The current project builds on our success in applying combined molecular and systems biology study and further explores the regulation of root development under osmotic stress conditions.The project focuses on the question "How does osmotic stress regulate the size of the root meristem". It will deliver rigorous training across a broad range of molecular and systems biology areas. It will develop skills in both molecular biology and systems biology. This includes all or some following skills: RNA extraction and cDNA synthesis; quantitative real-time polymerase chain reaction (qPCR); compound light microscopy; confocal laser scanning microscopy; living imaging system; image analysis; network construction; computer software; and various modelling techniques. An important feature of this project is to employ a combined molecular and systems biology study to explore the complexity in the regulation of root growth under osmotic stress.