A Plant-Specific N-terminal Extension Reveals Evolutionary Functional Divergence within Translocator Proteins

Pawel Jurkiewicz; Lucile Senicourt; Haitham Ayeb; Olivier Lequin; Jean-Jacques Lacapere; Henri Batoko

doi:10.1016/j.isci.2020.100889

A Plant-Specific N-terminal Extension Reveals Evolutionary Functional Divergence within Translocator Proteins

iScience. 2020 Mar 27;23(3):100889. doi: 10.1016/j.isci.2020.100889. Epub 2020 Feb 7.

Authors

Pawel Jurkiewicz¹, Lucile Senicourt², Haitham Ayeb¹, Olivier Lequin², Jean-Jacques Lacapere², Henri Batoko³

Affiliations

¹ Louvain Institute of Biomolecular Science and Technology (LIBST), University of Louvain (UCLouvain), Croix du Sud 4-5, L7.07.14, 1348 Louvain-la-Neuve, Belgium.
² Sorbonne Université, École Normale Supérieure, PSL University, CNRS, Laboratoire des Biomolécules, 4 Place Jussieu, 75005 Paris, France.
³ Louvain Institute of Biomolecular Science and Technology (LIBST), University of Louvain (UCLouvain), Croix du Sud 4-5, L7.07.14, 1348 Louvain-la-Neuve, Belgium. Electronic address: henri.batoko@uclouvain.be.

Abstract

Conserved translocator proteins (TSPOs) mediate cell stress responses possibly in a cell-type-specific manner. This work reports on the molecular function of plant TSPO and their possible evolutionary divergence. Arabidopsis thaliana TSPO (AtTSPO) is stress induced and has a conserved polybasic, plant-specific N-terminal extension. AtTSPO reduces water loss by depleting aquaporin PIP2;7 in the plasma membrane. Herein, AtTSPO was found to bind phosphoinositides in vitro, but only full-length AtTSPO or chimeric mouse TSPO with an AtTSPO N-terminus bound PI(4,5)P₂in vitro and modified PIP2;7 levels in vivo. Expression of AtTSPO but not its N-terminally truncated variant enhanced phospholipase C activity and depleted PI(4,5)P₂ from the plasma membrane and its enrichment in Golgi membranes. Deletion or point mutations within the AtTSPO N-terminus affected PI(4,5)P₂ binding and almost prevented AtTSPO-PIP2;7 interaction in vivo. The findings imply functional divergence of plant TSPOs from bacterial and animal counterparts via evolutionary acquisition of the phospholipid-interacting N-terminus.

Keywords: Cell Biology; Plant Biology; Plant Physiology.