Keeping meristems at balance – stem cell maintenance and termination in flowers with two meristem types

维持花分生组织中干细胞的活性是花的基本结构建立所必需的。大多数植物的花中只存在一种花分生组织，花器官以一种简单、直接的方式依次启动，形成花器官的轮状排列。有些植物产生第二个环状分生组织，即使在中心花分生组织在心皮发育过程中停止后，其长期的活动也允许产生雄蕊。这种进化的新颖性导致了一种更灵活的生长模式，允许在花发育后期调整雄蕊数量。环状分生系统形成的分子基础尚不清楚，但很可能是异位表达、替代重布线和干细胞决定程序的模式被修改。该项目的目的是获得对两个相邻分生系统的发展和维持的机制见解。此外，我们旨在阐明环状分生组织起源的分子基础。我们想比较两个密切相关的罂粟科植物，一个有（Eschscholzia californica）和一个没有环分生组织（Pteridophyllum racemosum），关于1)调节分生组织干细胞活性的基因，2)它们的表达模式和遗传功能。此外，我们的目标是3)确定不同分生组织类型的异同点；4)希望在分子尺度上了解环形分生组织起源的进化过程。我们相信，该项目的启动将大大提高我们对“干细胞活性的维持”、“新型分生组织类型的起源”、“花的基本结构多样化的分子基础”等重要生物学问题的认识，并深入到解决雌雄生殖结构之间资源分配的分子基础的基本生态学问题。

The maintenance of stem cell activity in the floral meristem is required for the establishment of the basic structure of a flower. Only one type of floral meristem exists in the flowers of most plants, from which floral organs initiate successively in a simple, straightforward way generating a whorled arrangement of floral organs. Some plants produce a second, ring-like meristem whose prolonged activity allows the production of stamens even after the central floral meristem ceased in the process of carpel development. This evolutionary novelty leads to a more flexible growth mode allowing adjustment of stamen number until late in flower development.The molecular basis underlying the formation of the ring meristem is unclear, yet it is very likely that ectopic expression, alternative rewiring and patterning of the stem cell determination program is modified. The aim of this project is to obtain mechanistic insights into the development and maintenance of two neighboring meristems. Moreover, we aim to elucidate the molecular base of ring meristem origin. We want to compare two closely related Papaveraceae species, one with (Eschscholzia californica) and one without ring meristem (Pteridophyllum racemosum) regarding 1) genes regulating the stem cell activity of meristems, 2) their expression pattern and genetic functions. In addition, we 3) aim to identify the similarities and differences of the distinct meristem types and 4) want to understand the evolutionary processes leading to the origin of the ring meristem at the molecular scale. We believe that launching this project will significantly improve our understanding of essential biological issues such as “the maintenance of stem cell activity”, “the origin of novel meristem types”, “the molecular basis of flower diversification in basic structure”, and reaches into the basic ecological question addressing the molecular base for resource allocation between male and female reproductive structures.