A Reservoir of Pluripotent Phloem Cells Safeguards the Linear Developmental Trajectory of Protophloem Sieve Elements

First author: Bojan Gujas; Affiliations: Swiss Federal Institute of Technology Zurich (苏黎世联邦理工学院): Zurich, Switzerland

Corresponding author: Antia Rodriguez-Villalon

Plant cells can change their identity based on positional information, a mechanism that confers developmental plasticity to plants. This ability, common to distinct multicellular organisms, is particularly relevant for plant phloem cells. Protophloem sieve elements (PSEs), one type of phloem conductive cells, act as the main organizers of the phloem pole, which comprises four distinct cell files organized in a conserved pattern. Here, we report how Arabidopsis roots generate a reservoir of meristematic phloem cells competent to swap their cell identities. Although PSE misspecification induces cell identity hybridism, the activity of RECEPTOR LIKE PROTEIN KINASE 2 (RPK2) by perceiving CLE45 peptide contributes to restrict PSE identity to the PSE position. By maintaining a spatiotemporal window when PSE and PSE-adjacent cells’ identities are interchangeable, CLE45 signaling endows phloem cells with the competence to re-pattern a functional phloem pole when protophloem fails to form.

植物细胞能够基于所处的位置信息改变自身的身份（cell identity），因此植物具有非常高的发育可塑性。这项多细胞生物共有的能力，在植物的韧皮部细胞中更为明显。原生韧皮部筛管元件PSEs是一类韧皮部传导细胞，作为韧皮部极的主要组织者，韧皮部传导细胞主要包含了四种不同的细胞类型，以一个十分保守的模式构成。本文中，作者发现拟南芥的根会形成一个具有分生能力的韧皮部细胞池用来互换细胞身份。尽管PSE的错误特化会导致细胞身份的混乱，由CLE45感知的类受体蛋白激酶RPK2活性作用于将PSE identity限制于PSE所在的区域。通过维持一个PSE与邻近细胞之间的身份互换的时空窗口，CLE45信号通路保证了在原生韧皮部细胞不能正常形成一个功能性韧皮部极时，赋予韧皮部细胞形成一个具有功能性的韧皮部极的能力。

p.s. 韧皮部传导细胞：protophloem sieve element（原生韧皮部筛管元件PSE）、companion cell（伴随细胞CC）、metaphloem sieve element（后生韧皮部筛管元件MSE）和protophloem pole pericycle cell (原生韧皮部极中柱鞘细胞PPP)。

A conserved pattern：

通讯：Antia Rodriguez-Villalon (https://impb.ethz.ch/research/research-pvd.html)

研究方向：原生韧皮部细胞中磷酸肌醇介导的细胞器降解；建立磷酸肌醇相关的功能信号传导网络并理解其作用于细胞命运决定的功能。

doi: https://doi.org/10.1016/j.cub.2019.12.043

Journal: Current Biology

Published online: February 06, 2020