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Mechanisms and Effects of Retention of Over‐Expressed Aquaporin AtPIP2;1 in the Endoplasmic Reticulum
Author(s) -
Sorieul Mathias,
Santoni Véronique,
Maurel Christophe,
Luu DoanTrung
Publication year - 2011
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2010.01154.x
Subject(s) - fluorescence recovery after photobleaching , endoplasmic reticulum , arabidopsis , green fluorescent protein , mcherry , er retention , microbiology and biotechnology , aquaporin , golgi apparatus , biology , intracellular , mutant , transport protein , biophysics , membrane , biochemistry , gene
Plasma membrane intrinsic proteins (PIPs) are aquaporins that mediate water transport across the plant plasma membrane (PM). The present work addresses, using Arabidopsis At PIP2;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 At PIP2;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 At PIP2;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 At PIP2;1‐GFP constructs reduced the root hydraulic conductivity. Co‐expression of At PIP2;1‐GFP and At PIP1;4‐mCherry constructs suggested that ER‐retained At PIP2;1‐GFP may interact with other PIPs to hamper their trafficking to the PM, thereby contributing to inhibition of root cell hydraulic conductivity.