Crossing paths: Investigating the role of auxin and cytokinin in 3D growth specification

历史上最重要的事件之一是大约4.7亿年前植物对陆地的殖民。这种转变与三维（3D）生长的进化相吻合，并且很可能是由其促进的。三维生长是所有陆地植物的一个不变的关键特征，全球范围内表现出的不同形态是三维生长过程不同调控的结果。然而，我们对3D生长是如何在基因水平上被调节的知之甚少。利用开花植物研究三维生长是困难的，因为三维生长开始于合子的前几次分裂。因此，破坏这些植物的三维生长将导致胚胎致命，并为实验研究提供了一个狭窄的时间框架。相反，在苔藓中，三维生长（配子体发育）之前是一个延长的二维（2D）丝状阶段，可以无限期地培养。P. patens不需要启动3D生长来存活，因此是一个理想的模型系统来遗传解剖3D生长。从2D到3D的生长转变依赖于生长素和细胞分裂素的信号传导，伴随着细胞分裂平面方向的高度协调变化，最终形成具有径向组织的叶状phyllids的配子体。生长素在广泛的发育背景下一直与细胞分裂平面定向有关，并被认为是配子体发育过程中分裂平面定向的“指导性信号”。我们已经分离出了一些“无配子体”（nog）突变体，这些突变体不能指定3D生长，因为它们在细胞分裂方向上表现出缺陷。该提案将利用这些“nog”突变体来揭示支撑P. patens从2D到3D生长转变的复杂生长素-细胞分裂素串扰，并将为植物3D生长的调控提供前所未有的见解。项目目标：-鉴定无配子体（nog）突变体中不能指定3D生长的突变-表征nog突变体中生长素和细胞分裂素的反应并获得转录组-通过细胞特异性破坏生长素/细胞分裂素信号传导来重现3D生长缺陷

One of the most important events in history was the colonization of land by plants approximately 470 million years ago. This transition coincided with, and was likely facilitated by, the evolution of 3-dimensional (3D) growth. 3D growth is an invariable and pivotal feature of all land plants, and the diverse morphologies exhibited across the globe are a result of the differential regulation of 3D growth processes. Yet, we know very little about how 3D growth is regulated at the genetic level.Studies of 3D growth are difficult using flowering plants as 3D growth begins within the first few divisions of the zygote. Disrupting 3D growth in these plants would therefore cause embryo lethality and provide a narrow timeframe for experimental investigation. Conversely, in the moss Physcomitrium patens, 3D growth (gametophore development) is preceded by a protracted 2-dimensional (2D) filamentous phase that can be cultured indefinitely. P. patens does not need to initiate 3D growth to survive, and thus is an ideal model system to genetically dissect 3D growth. The 2D to 3D growth transition in P. patens is dependent on auxin and cytokinin signaling, is accompanied by highly coordinated changes in cell division plane orientation and culminates in the formation of gametophores with radially organised leaf-like phyllids. Auxin has been consistently implicated in cell division plane orientation within a broad range of developmental contexts and has been implicated as the 'instructive signal' for division plane orientation in developing gametophores.We have isolated a number of 'no gametophores' (nog) mutants that fail to specify 3D growth because they exhibit defects in cell division orientation. This proposal will exploit these 'nog' mutants to unravel the complex auxin-cytokinin crosstalk underpinning the 2D to 3D growth transition in P. patens and will provide unprecedented insight into the regulation of 3D growth in plants.Project Objectives:-Identify the mutations in no gametophore' (nog) mutants that fail to specify 3D growth- Characterize the auxin and cytokinin responses in nog mutants and obtain transcriptomes-Recapitulate 3D growth defects through cell-specific disruption of auxin/cytokinin signaling