title: Root K(+) acquisition in plants: the Arabidopsis thaliana model.
abstract: K(+) is an essential macronutrient required by plants to complete their life cycle. It fulfills important functions and it is widely used as a fertilizer to increase crop production. Thus, the identification of the systems involved in K(+) acquisition by plants has always been a research goal as it may eventually produce molecular tools to enhance crop productivity further. This review is focused on the recent findings on the systems involved in K(+) acquisition. From Epstein's pioneering work >40 years ago, K(+) uptake was considered to consist of a high- and a low-affinity component. The subsequent molecular approaches identified genes encoding K(+) transport systems which could be involved in the first step of K(+) uptake at the plant root. Insights into the regulation of these genes and the proteins that they encode have also been gained in recent studies. A demonstration of the role of the two main K(+) uptake systems at the root, AtHKA5 and AKT1, has been possible with the study of Arabidopsis thaliana T-DNA insertion lines that knock out these genes. AtHAK5 was revealed as the only uptake system at external concentrations <10 μM. Between 10 and 200 μM both AtHAK5 and AKT1 contribute to K(+) acquisition. At external concentrations >500 μM, AtHAK5 is not relevant and AKT1's contribution to K(+) uptake becomes more important. At 10 mM K(+), unidentified systems may provide sufficient K(+) uptake for plant growth.
authors.affiliation: Centro de Edafología y Biología Aplicada del Segura-CSIC, Campus de Espinardo, 30100 Murcia, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Alemán
authors.forename: Manuel
authors.initials: M
authors.lastname: Nieves-Cordones
authors.forename: Vicente
authors.initials: V
authors.lastname: Martínez
authors.forename: Francisco
authors.initials: F
authors.lastname: Rubio
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D016254:Mutagenesis, Insertional; D018517:Plant Roots / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters; D012323:RNA Processing, Post-Transcriptional; D027981:Symporters / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D015221:Potassium Channels; D027961:Potassium-Hydrogen Antiporters; D027981:Symporters; C036483:T-DNA; C501258:potassium transporter, Arabidopsis; C074500:AKT1 protein, Arabidopsis; D011188:Potassium