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Title: Non‐selective cation channel activity of aquaporin AtPIP2;1 regulated by Ca 2+ and pH
Abstract

The aquaporin AtPIP2;1 is an abundant plasma membrane intrinsic protein inArabidopsis thalianathat is implicated in stomatal closure, and is highly expressed in plasma membranes of root epidermal cells. When expressed inXenopus laevisoocytes, AtPIP2;1 increased water permeability and induced a non‐selective cation conductance mainly associated with Na+. A mutation in the water pore, G103W, prevented both the ionic conductance and water permeability of PIP2;1. Co‐expression of AtPIP2;1 with AtPIP1;2 increased water permeability but abolished the ionic conductance. AtPIP2;2 (93% identical to AtPIP2;1) similarly increased water permeability but not ionic conductance. The ionic conductance was inhibited by the application of extracellular Ca2+and Cd2+, with Ca2+giving a biphasic dose–response with a prominent IC50of 0.32 mм comparable with a previous report of Ca2+sensitivity of a non‐selective cation channel (NSCC) in Arabidopsis root protoplasts. Low external pH also inhibited ionic conductance (IC50pH 6.8).Xenopusoocytes andSaccharomyces cerevisiaeexpressing AtPIP2;1 accumulated more Na+than controls. Establishing whether AtPIP2;1 has dual ion and water permeabilityin plantawill be important in understanding the roles of this aquaporin and if AtPIP2;1 is a candidate for a previously reported NSCC responsible for Ca2+and pH sensitive Na+entry into roots.

 
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PAR ID:
10038184
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Plant, Cell & Environment
Volume:
40
Issue:
6
ISSN:
0140-7791
Page Range / eLocation ID:
p. 802-815
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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