title: Mechanisms and effects of retention of over-expressed aquaporin AtPIP2;1 in the endoplasmic reticulum.
abstract: Plasma membrane intrinsic proteins (PIPs) are aquaporins that mediate water transport across the plant plasma membrane (PM). The present work addresses, using Arabidopsis AtPIP2;1 as a model, the mechanisms and significance of trafficking of newly synthesized PIPs from the endoplasmic reticulum (ER) to the Golgi apparatus. A functional diacidic export motif (Asp4-Val5-Glu6) was identified in the N-terminal tail of AtPIP2;1, using expression in transgenic Arabidopsis of site-directed mutants tagged with the green fluorescent protein (GFP). Confocal fluorescence imaging and a novel fluorescence recovery after photobleaching application based on the distinct diffusion of PM and intracellular AtPIP2;1-GFP forms revealed a retention in the ER of diacidic mutated forms, but with quantitative differences. Thus, the individual role of the two acidic Asp4 and Glu6 residues was established. In addition, expression in transgenic Arabidopsis of ER-retained AtPIP2;1-GFP constructs reduced the root hydraulic conductivity. Co-expression of AtPIP2;1-GFP and AtPIP1;4-mCherry constructs suggested that ER-retained AtPIP2;1-GFP may interact with other PIPs to hamper their trafficking to the PM, thereby contributing to inhibition of root cell hydraulic conductivity.
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, F-34060 Montpellier Cedex 2, France.
authors.forename: Mathias
authors.initials: M
authors.lastname: Sorieul
authors.forename: Véronique
authors.initials: V
authors.lastname: Santoni
authors.forename: Christophe
authors.initials: C
authors.lastname: Maurel
authors.forename: Doan-Trung
authors.initials: DT
authors.lastname: Luu
mesh_terms: D020816:Amino Acid Motifs; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006056:Golgi Apparatus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D021381:Protein Transport; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C491680:plasma membrane intrinsic protein 2 Arabidopsis; D014867:Water; D049452:Green Fluorescent Proteins