Establishment and Maintenance of the Barley Inflorescence Meristem

植物干细胞代表未分化的分生组织，注定在胚胎后分裂并提供生长。在生长发育过程中，特定的细胞系进一步分化，最终形成器官和整个植物。胚源根尖分生组织（RAM）和芽尖分生组织（SAM）是植物最早形成的分生组织。根据环境和位置线索，来自SAM的细胞采用策略来指定所谓的次生分生组织，从而形成整个地上植物的结构。第一个生殖分生组织，即花序分生组织（IM），为所有花的变异提供了基础。有趣的是，在所有这些模式和形态发生的早期发育事件中，激素调控与转录调控协同作用驱动发育；事实上，其中一个重要的调节因子属于同源结构域（HD）家族，该家族含有WOX （wuschell相关同源盒）蛋白，在干细胞生态位模式、细胞分裂和器官形成过程中定义各种作用。在谷类作物中，与拟南芥相比，对IM的建立、维持和信号传导还没有很好的了解。在包括大麦（Hordeum vulgare L.）在内的许多重要谷类作物中，关于SAM / IM干细胞生态位、组织细胞或外周区定位的基本知识完全缺失。如果我们想更好地了解大麦花序（称为穗）是如何形成的，那么对茎尖的细胞模式的更基本的了解显然是必不可少的。本研究项目的主要工作假设是大麦WOX （HvWOX）基因在大麦IM的建立和维持过程中发挥了重要作用，并且在大麦（可能还有小麦）中发生了新的进化和分化的HvWOX基因调控。因此，该项目寻求(i)更深入地了解小麦/草WOX蛋白的系统发育，（ii）获得相关HvWOX和潜在干细胞标记基因的精细和细胞解析转录分析，（iii）使用HvWOX转基因报告系检查细胞定位以及细胞间运动，最后（iv）表征突变的HvWOX基因的表型。

Plant stem cells represent undifferentiated meristematic tissue destined to divide and to provide growth postembryonically. During growth and development specified cell lineages further differentiate, ultimately forming organs and the entire plant. The embryo-derived root apical meristem (RAM) and the shoot apical meristem (SAM) are the first plant meristems formed. Depending on environmental and positional cues, cells from the SAM adopt strategies to specify so called secondary meristems, thereby shaping overall above-ground plant architecture. The first reproductive meristem, i.e. inflorescence meristem (IM), provides the foundation for all floral variation. Intriguingly, in all of these early developmental events of patterning and morphogenesis, hormonal regulation in concerted action together with transcriptional regulators drive development; in fact, one of such important regulators belongs to the family of homeodomain (HD) containing WOX (WUSCHEL-related homeobox) proteins that define various roles during stem cell niche patterning, cell division and organ formation.In cereal crops IM establishment, maintenance and signaling are not at all well understood, as compared to Arabidopsis. Fundamental knowledge in terms of cellular positioning of the SAM / IM stem cell niche, organizing cells or peripheral zone is completely missing in many important cereal crops including barley (Hordeum vulgare L.). If we want to better understand how a barley inflorescence, called spike, is formed, a more fundamental insight into the cellular patterning of the shoot apex is clearly essential.The major working hypothesis of this research project is that barley WOX (HvWOX) genes play an important role during the establishment and maintenance of the barley IM, and that newly evolved and diverged HvWOX gene regulation has occurred in barley (and possibly Triticeae). This project therefore seeks (i) deeper insights into the Triticeae/grass WOX protein phylogeny, (ii) to obtain a refined and cell-resolved transcript analyses of relevant HvWOX and potential stem cell marker genes, (iii) to use HvWOX transgenic reporter lines to check cellular localization as well as cell-to-cell movement, and finally (iv) to characterize mutated HvWOX genes phenotypically.