Mechanisms of proximo-distal polarity establishment and tissue patterning in Hibiscus petals

博士项目战略主题：了解生命的规则开花植物花瓣上的彩色图案是吸引传粉者的关键，并直接参与物种的繁殖成功。这些模式通常是高度复杂的，并且联合收割机结合了色素沉着、细胞形状和角质层的分化差异，因此它们的发育必须受到严格调控，以产生具有不同特性的邻近组织。在花瓣表皮的生长过程中，这种清晰的边界是如何建立起来的还有待了解。塞恩斯伯里实验室（剑桥大学）的Moyroud小组开发了一种木槿属植物作为一种新的模型系统，以了解这些图案是如何在花瓣上形成的。使用转录组学方法，他们确定了在图案形成之前的非常早期的发育阶段，其表达仅限于花瓣的不同部分的基因。建议的研究计划旨在（i）测试一个新的假设，即有关花瓣基部至顶端极性的信号的性质;（ii）探索花瓣中细胞极性和组织极性之间的相互作用;以及（iii）确定负责图案形成的下游基因调控网络。为此，一系列分子生物学技术将与新兴模型系统中最先进的遗传操作相结合（克隆，定量PCR，构建过表达和CRISPR/Cas9敲除Hibiscus系，生产表达感兴趣代谢物和转录组学的荧光传感器的转基因植物）。该项目还将涉及外部分析：候选分子将被应用于植物中或分离花瓣上的发育芽，使用定制的体外花瓣生长系统来评估它们干扰花瓣图案的能力。最后，共聚焦，拉曼和扫描电子显微镜方法将被用来分析表型的处理芽/花瓣，转基因株系和突变体的图案形成缺陷，最近在遗传筛选中确定。

PhD project strategic theme: Understanding the rules of life The colourful patterns on the petal of flowering plants are key to attracting pollinators and participate directly in the reproductive success of a species. These patterns are often highly elaborate and combine differences in pigmentation, cell shape and ornamentation of the cuticle so their development must be tightly regulated to generate neighbouring tissues with distinct properties. How such clear boundaries are established within the petal epidermis as it grows remains to be understood.The Moyroud group at the Sainsbury Laboratory (University of Cambridge) has developed a species of Hibiscus as a new model system to understand how those patterns form on petals. Using a transcriptomic approach, they identified genes whose expression is restricted to distinct parts of the petal in very early stages of development, before pattern formation. Those constitute candidate genes likely to act as upstream regulators of pattern formation.The proposed project will aim at (i) testing a new hypothesis regarding the nature of the signal that organises the petal base-to-tip polarity, (ii) exploring the interplay between cell polarity and tissue polarity in petals, and (iii) identifying the downstream gene regulatory network(s) responsible for pattern formation. To do so, a range of molecular biology techniques will be used in combination with state-of-the art genetic manipulations in an emerging model system (cloning, quantitative PCR, construction of overexpression and CRISPR/Cas9 knock-out Hibiscus lines, production of transgenic plants expressing fluorescent sensors for metabolites of interest and transcriptomics). This project will also involve external assays: candidate molecules will be applied to developing buds in planta or on isolated petals using a custom-made in vitro petal growth system to assess their ability to interfere with petal patterning. Finally, confocal, Raman and scanning electron microscopy methods will be used to analyse phenotypes of treated buds/petals, transgenic lines and mutants with defect in pattern formation recently identified in a genetic screen.