The Shape of Plants: exploring developmental transitions

植物进化了感觉和反应机制，以在不同和不利的环境条件下优化生长和发育。植物体内称为分生组织的微小区域维持干细胞处于静止状态，并产生形成组织和器官的细胞。细胞从分生组织中移位，但最终停止分裂并经历大规模生长。从分裂到分化的这种转变发生的时间和地点决定了植物器官的最终大小和形状，并受到普遍环境条件的强烈影响，并受到干旱和盐分等胁迫的影响。本研究计划的首要目标是识别和理解植物决定和协调从增殖到分化的发育转变的机制。它还建立在对称为微管(MTS)的动态亚细胞细丝的特性和功能的三十多年研究的基础上。MTS在所有真核生物中都是进行染色体分离、细胞内转运、定向生长和运动所必需的。这项研究分为三个子项目，每个子项目都专注于(在MT功能的背景下)发育转变。*我们将首先确定两种类型的MT相关蛋白MOR1和ARK如何协同工作来协调MT的组装和拆卸。我们将确定这些蛋白质如何在细胞从一个发育阶段过渡到另一个发育阶段时控制MT的动态，以及对盐胁迫的反应，这涉及到瞬时的MT分解。第二个目标将阐明MT相关蛋白CLAP和生长激素油菜素类固醇如何控制从增殖到分化的转变。我们最近发现，CLAP通过促进其受体的循环来维持油菜素类固醇信号，但油菜素类固醇信号也下调了CLAP。为了进一步探索这种负反馈循环，我们对CLASP基因不再对油菜素类固醇做出反应的植物进行了改造。这些“非偶联的”植物将成为确定CLAP在调节增殖-分化转换点中所起作用的强大工具。*最后，我们将探索膜锚定的纤维素结合蛋白COBRA如何在细胞扩张过程中维持单向生长。眼镜蛇在快速扩张过程中高度表达，是生产纤维素所必需的，而纤维素是植物细胞壁的主要张力承受力成分。我们最近证实了COBRA存在于细胞壁中，但也发现它与合成纤维素的酶复合体有关，这些酶复合体分布在细胞内的MT上。我们将使用生化和转录分析来验证我们的假设，即眼镜蛇在与纤维素相互作用后经历切割，以及它随后与纤维素合成酶复合体的关联调节纤维素的产生。

Plants have evolved sensory and response mechanisms to optimize growth and development under diverse and adverse environmental conditions. Tiny regions of the plant body called meristems maintain stem cells in a quiescent state, and produce the cells that give rise to tissues and organs. Cells are displaced from the meristem, but eventually stop dividing and undergo massive growth. When and where this transition from division to differentiation occurs determines the ultimate size and shape of plant organs, and is strongly influenced by prevailing environmental conditions, and modified by stresses such as drought and salinity.******The overarching goal of this research proposal is to identify and understand the mechanisms by which plants determine and coordinate the developmental transition from proliferation to differentiation. It also builds on more than three decades of research on the properties and functions of dynamic sub-cellular filaments called microtubules (MTs). MTs are essential in all eukaryotic organisms for carrying out chromosome separation, intracellular transport, directional growth and motility. The research is divided into three subprograms, each of which focusses on developmental transitions (in the context of MT function).******We will first determine how two types of MT-associated proteins, MOR1 and ARK, work in concert to coordinate MT assembly and disassembly. We will determine how these proteins control MT dynamics as cells transition from one stage of development to another, but also in response to salt stress, which involves transient MT disassembly.******The second objective will elucidate how the MT-associated protein CLASP and the growth hormone brassinosteroid control the transition from proliferation to differentiation. We recently discovered that CLASP sustains brassinosteroid signalling by fostering the recycling of its receptors but that brassinosteroid signalling also down-regulates CLASP. To explore this negative feedback loop further, we have engineered plants in which the CLASP gene is no longer responsive to brassinosteroids. These 'uncoupled' plants will be powerful tools for identifying the specific function CLASP plays in modulating the proliferation-differentiation transition point.******Finally, we will explore how the membrane-anchored cellulose-binding protein COBRA sustains unidirectional growth during cell expansion. COBRA is highly expressed during rapid expansion and is required for the production of cellulose, which is the major tension-bearing component of plant cell walls. We recently confirmed COBRA's presence in the cell wall, but also discovered that it associates with the enzyme complexes that synthesize cellulose, which are distributed along MTs inside the cell. We will use biochemical and transcriptional assays to test our hypothesis that COBRA undergoes cleavage after interacting with cellulose, and that its subsequent association with the cellulose synthase complex modulates cellulose production.********