Submitted to: Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2006
Publication Date: 5/11/2006
Citation: Shigaki, T., Hirschi, K.D. 2006. Diverse functions and molecular properties emerging for CAX Cation/H+ exchangers in plants. Plant Biology. 8(4):419-429. Interpretive Summary: There has been a rapid advancement in research on a group of mineral transporters called CAXs (CAtion eXchangers). CAXs are thought to play major roles in plant nutrition and stress responses. CAX transporters regulate the removal of calcium from the cytosol at its N-terminus, and this mechanism appears to be universal in all CAXs. Recent mutational studies indicate that local amino acid variations specify the ions they transport, which may be of great importance when we design artificial transporters that are tailored to transport ions of specific interest. Despite the original description of CAXs as calcium transporters, they appear now to accept many different ions, indicating the multifaceted physiological roles in plants, which will be a focus of future studies.
Technical Abstract: Steep concentration gradients of many ions are actively maintained, with lower concentrations typically located in the cytosol, and higher concentrations in organelles and outside the cell. The vacuole is an important storage organelle for many ions. The concentration gradient of cations is established across the plant tonoplast, in part, by high-capacity cation/H[+] (CAX) exchange activity. While plants may not be green yeast, analysis of CAX regulation and substrate specificity has been greatly aided by utilizing yeast as an experimental tool. The basic CAX biology in "Arabidopsis" has immediate relevance toward understanding the functional interplay between diverse transport processes. The long-range applied goals are to identify novel transporters and express them in crop plants in order to "mine" nutrients out of the soil and into plants. In doing so, this could boost the levels of essential nutrients in plants.