The Arabidopsis cax1 mutant exhibits impaired ion homeostasis,development, and hormonal responses and reveals interplay among vacuolar transporters |
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| Authors: | Cheng Ning-Hui Pittman Jon K Barkla Bronwyn J Shigaki Toshiro Hirschi Kendal D |
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| Affiliation: | United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA. |
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| Abstract: | The Arabidopsis Ca(2+)/H(+) transporter CAX1 (Cation Exchanger1) may be an important regulator of intracellular Ca(2+) levels. Here, we describe the preliminary localization of CAX1 to the tonoplast and the molecular and biochemical characterization of cax1 mutants. We show that these mutants exhibit a 50% reduction in tonoplast Ca(2+)/H(+) antiport activity, a 40% reduction in tonoplast V-type H(+)-translocating ATPase activity, a 36% increase in tonoplast Ca(2+)-ATPase activity, and increased expression of the putative vacuolar Ca(2+)/H(+) antiporters CAX3 and CAX4. Enhanced growth was displayed by the cax1 lines under Mn(2+) and Mg(2+) stress conditions. The mutants exhibited altered plant development, perturbed hormone sensitivities, and altered expression of an auxin-regulated promoter-reporter gene fusion. We propose that CAX1 regulates myriad plant processes and discuss the observed phenotypes with regard to the compensatory alterations in other transporters. |
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