Root development under metal stress in Arabidopsis thaliana requires the H+/cation antiporter CAX4.
* The Arabidopsis vacuolar CAtion eXchangers (CAXs) play a key role in mediating cation influx into the vacuole. In Arabidopsis, there are six CAX genes. However, some members are yet to be characterized fully. * In this study, we show that CAX4 is expressed in the root apex and lateral root primordia, and that expression is increased when Ni(2+) or Mn(2+) levels are elevated or Ca(2+) is depleted. * Transgenic plants expressing increased levels of CAX4 display symptoms consistent with increased sequestration of Ca(2+) and Cd(2+) into the vacuole. When CAX4 is highly expressed in an Arabidopsis cax1 mutant line with weak vacuolar Ca(2+)/H(+) antiport activity, a 29% increase in Ca(2+)/H(+) antiport is measured. A cax4 loss-of-function mutant and CAX4 RNA interference lines display altered root growth in response to Cd(2+), Mn(2+) and auxin. The DR5::GUS auxin reporter detected reduces auxin responses in the cax4 lines. * These results indicate that CAX4 is a cation/H(+) antiporter that plays an important function in root growth under heavy metal stress conditions.
Mei
Hui
H
Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX 77845, USA.
Cheng
Ning Hui
NH
United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.
Zhao
Jian
J
United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.
Park
Sunghun
S
Department of Horticulture, Forestry and Recreation Resources, Kansas State University, Manhattan, KS 66506, USA.
Escareno
Rito A
RA
St Edward's University, Austin, TX 78704, USA.
Pittman
Jon K
JK
Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
Hirschi
Kendal D
KD
Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX 77845, USA.|United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.
D000222:Adaptation, Physiological / Q000235:genetics*; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D019216:Metals, Heavy / Q000378:metabolism* / Q000633:toxicity; D009154:Mutation; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics; D014617:Vacuoles / Q000378:metabolism
D017920:Antiporters; D029681:Arabidopsis Proteins; C460090:CAX4 protein, Arabidopsis; D027682:Cation Transport Proteins; D007210:Indoleacetic Acids; D019216:Metals, Heavy