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Plant cation/H+ exchangers (CAXs): biological functions and genetic manipulations

Authors

  • M. Manohar,

    1.  United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, TX, USA
    2.  Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX, USA
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  • T. Shigaki,

    1.  Papua New Guinea National Agricultural Research Institute, Bubia, Lae, Papua, New Guinea
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  • K. D. Hirschi

    1.  United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, TX, USA
    2.  Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX, USA
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  • Editor
    A. Weber

K. D. Hirschi, Children’s Nutrition Research Center, 1100 Bates, Room 9016, Houston, TX 77030, USA.
E-mail: kendahl@bcm.edu

Abstract

Inorganic cations play decisive roles in many cellular and physiological processes and are essential components of plant nutrition. Therefore, the uptake of cations and their redistribution must be precisely controlled. Vacuolar antiporters are important elements in mediating the intracellular sequestration of these cations. These antiporters are energized by the proton gradient across the vacuolar membrane and allow the rapid transport of cations into the vacuole. CAXs (for CAtion eXchanger) are members of a multigene family and appear to predominately reside on vacuoles. Defining CAX regulation and substrate specificity have been aided by utilising yeast as an experimental tool. Studies in plants suggest CAXs regulate apoplastic Ca2+ levels in order to optimise cell wall expansion, photosynthesis, transpiration and plant productivity. CAX studies provide the basis for making designer transporters that have been used to develop nutrient enhanced crops and plants for remediating toxic soils.

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