Decoding the Lateral Expansion of Plant Stems

与成年个体的组织增殖通常是病理性和有害的动物相反，植物已经进化出无限期的生长习性。在这方面特别值得注意的是植物茎和根的增厚，因为这是一个纯粹的胚后生长过程，并且干细胞的负责组形成层嵌入高度分化的组织中。因此，植物的横向生长必须整合和克服周围组织所隐含的物理约束，并引起其性质的根本变化。参与组织如何沟通以建立如此复杂的生长过程是完全未知的。在这里，我们将探讨过程中的参考植物拟南芥作为一个范例胚后生长过程的侧茎生长。我们将通过分析每个干组织在侧向生长开始前后的转录组来研究细胞行为。细胞壁固定植物细胞相对于彼此的位置，并且它们的刚性对于植物体的机械支撑是必不可少的。因此，我们将进一步研究细胞壁修饰在植物横向生长调节中的作用，并通过使用正向遗传学来识别将细胞壁状态转化为细胞动力学变化的新型信号级联。总之，这些方法将提供前所未有的了解横向茎生长，一个过程负责木材生产和积累的一大部分陆地生物量。因此，该项目将系统地描述一个未被探索但中心植物器官的发育，并揭示多细胞生物生长过程的基本概念。

In contrast to animals in which tissue proliferation in adult individuals is often pathological and deleterious, plants have evolved an indefinite growth habit. Especially remarkable in this respect is the thickening of plant stems and roots, as this is a pure postembryonic growth process and the responsible group of stem cells, the cambium, is embedded in highly differentiated tissues. Consequently, lateral plant growth has to integrate and overcome physical constraints implied by surrounding tissues and induce a fundamental change in their properties. How participating tissues communicate to establish such a complex growth process is completely unknown. Here we will explore the process of lateral stem growth in the reference plant Arabidopsis thaliana as a paradigm for postembryonic growth processes. We will study cell behavior by profiling the transcriptomes of each single stem tissue before and after lateral growth initiation. Cell walls fix the position of plant cells relative to each other and their rigidity is essential for mechanical support of the plant body. Therefore, we will additionally investigate the role of cell wall modifications in the regulation of lateral plant growth and identify by use of forward genetics novel signaling cascades that translate cell wall states into changes in cellular dynamics. Together, these approaches will provide unprecedented insight into lateral stem growth, a process responsible for wood production and the accumulation of a large proportion of terrestrial biomass. Thereby, this project will systemically characterize the development of an underexplored but central plant organ and reveal fundamental concepts of growth processes in multicellular organisms.