Bifacial cambium stem cells generate xylem and phloem during radial plant growth

First author: Dongbo Shi; Affiliations: Heidelberg University (德国海德堡大学): Heidelberg, Germany

Corresponding author: Thomas Greb

A reduced rate of stem cell division is considered a widespread feature which ensures the integrity of genetic information during somatic development of plants and animals. Radial growth of plant shoots and roots is a stem cell-driven process that is fundamental for the mechanical and physiological support of enlarging plant bodies. In most dicotyledonous species, the underlying stem cell niche, the cambium, generates xylem inwards and phloem outwards. Despite the importance and intriguing dynamics of the cambium, the functional characterization of its stem cells is hampered by the lack of experimental tools for accessing distinct cambium sub-domains. Here, we use the hypocotyl of Arabidopsis thaliana to map stem cell activity in the proliferating cambium. Through pulse labeling and genetically encoded lineage tracing, we find that a single bifacial stem cell generates both xylem and phloem cell lineages. This cell is characterized by a specific combination of PXY (TDR), SMXL5 and WOX4 gene activity and a high division rate in comparison with tissue-specific progenitors. Our analysis provides a cellular fate map of radial plant growth, and suggests that stem cell quiescence is not a general prerequisite for life-long tissue production.

干细胞分裂速率的减缓是确保动植物体细胞发育过程中遗传信息完整的普遍特征。植物茎和根的径向生长是由干细胞驱动的，该过程是植物长大后重要的机械和生理基础支撑。在大多数双子叶植物中，形成层作为潜在的干细胞龛会向内产生木质部，向外产生韧皮部。形成层除了具有这些非常重要的作用外，其干细胞的研究因为缺少能够将形成层亚结构分开的可用工具而受到很大的限制。本文，作者通过拟南芥的下胚轴来研究形成层增殖过程中的干细胞活性。通过脉冲标记和遗传编码的谱系追踪，作者发现了一个双功能的干细胞，既能产生木质部细胞，又能产生韧皮部细胞。作者通过PXY、SMXL5和WOX4三个基因的活性来标记该干细胞，以及比组织特异性祖细胞要高得多的细胞分裂率。本文的研究揭示了植物径向生长的细胞学基础，并且说明对于在整个生命周期一直在产生的组织来说干细胞静止并不是一个普遍的先决条件。

通讯：Thomas Greb (https://www.cos.uni-heidelberg.de/index.php/t.greb?l=_e)

研究方向：植物茎和根的径向生长。

doi: 10.1242/dev.171355

Journal: Development

Published date: January 09, 2019