Plasma Membrane Domain Patterning and Self-Reinforcing Polarity in Arabidopsis

First author: Petra Marhava; Affiliations: University of Lausanne (洛桑大学): Lausanne, Switzerland

Corresponding author: Christian S. Hardtke

Cell polarity is a key feature in the development of multicellular organisms. For instance, asymmetrically localized plasma-membrane-integral PIN-FORMED (PIN) proteins direct transcellular fluxes of the phytohormone auxin that govern plant development. Fine-tuned auxin flux is important for root protophloem sieve element differentiation and requires the interacting plasma-membrane-associated BREVIS RADIX (BRX) and PROTEIN KINASE ASSOCIATED WITH BRX (PAX) proteins. We observed “donut-like” polar PIN localization in developing sieve elements that depends on complementary, “muffin-like” polar localization of BRX and PAX. Plasma membrane association and polarity of PAX, and indirectly BRX, largely depends on phosphatidylinositol-4,5-bisphosphate. Consistently, mutants in phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks) display protophloem differentiation defects similar to brx mutants. The same PIP5Ks are in complex with BRX and display “muffin-like” polar localization. Our data suggest that the BRX-PAX module recruits PIP5Ks to reinforce PAX polarity and thereby the polarity of all three proteins, which is required to maintain a local PIN minimum.

细胞极性是多细胞生物生长发育的关键特征。比如说，不对称分布的质膜PIN蛋白直接指导细胞间植物激素生长素转运，而生长素是植物发育的重要调控因子。生长素的精确流动对于根的原生韧皮部筛分子的分化至关重要，并且需要与质膜相关BRX和PAX蛋白的互作。作者在发育中的筛分子中观察到了PIN蛋白类似于“甜甜圈”的极性分布，并且这种分布依赖于BRX和PAX蛋白完全相反的、类似于“松饼”的极性分布。PAX蛋白的质膜相关以及极性很大程度上都要依赖于磷脂酰肌醇-4,5-二磷酸磷脂酰肌醇-4,5-二磷酸，而BRX的极性分布则依赖于PAX蛋白。同样，磷脂酰肌醇-4-磷酸5-激酶PIP5Ks上的突变表现出与brx突变体类似的原生韧皮部分化缺陷。同样的PIP5Ks能够与BRX形成复合物，并且同样具有“松饼”的极性分布。本文的试验结果说明BRX-PAX模块通过招募PIP5Ks来增强PAX的极性，从而增强了这三个蛋白的极性，而这对于维持PIN蛋白的区域最小值是必需的。

通讯：Christian S. Hardtke (https://wp.unil.ch/hardtkelab)

个人简介：1997年，慕尼黑大学，博士；1998年，多伦多大学，博士后；1998-2000年，耶鲁大学，博士后。

研究方向：植物的生长和发育。

doi: https://doi.org/10.1016/j.devcel.2019.11.015

Journal: Developmental Cell

Published date: December 19, 2019