K+nutrition, uptake, and its role in environmental stress in plants

Abstract

The increasing world population makes high yield crop production a necessity in future agriculture. However, the negative effects of the emission of greenhouse gases into Earth's atmosphere and the resulting climate change may impede reaching this goal. New stresses will appear and the existing ones will be exacerbated. Important plant processes such as the acquisition of K+, which is an essential macronutrient for plants, will be negatively affected. The development of new crop varieties with enhanced capacities in the acquisition of K+, especially under the future environmental conditions, is an important challenge. One of the first steps may be the identification of the K+uptake systems operating in the roots, which may be later improved to enhance K+acquisition under stress conditions. Some gene families encoding K+transporters, that is, the HAK1-type, and channels, that is, the AKT1-type, key pieces for root K+uptake, have been identified. Members of other families of transport systems, such as the cation proton antiporter (CPA) family, or the cyclic nucleotide-gated channel (CNGC) family may also participate in that process. The use of T-DNA insertion lines in the model species Arabidopsis thaliana has allowed the demonstration of the role of some of these transport systems and, in some cases, the results obtained in the model plant also apply to crop species. Important points of the regulation of these transport systems are found at the transcriptional and the translational level. Internal K+concentrations, plasma membrane potential, reactive oxygen species (ROS), hormones, kinases, and phosphatases are involved in their regulation. The knowledge accumulated to date and that to be obtained in the future could be used in biotechnological approaches to produce more efficient K+transporters that endow plants with enhanced performance to face the future environmental challenges. Genetic engineering, natural variability, and the development of -omic technologies are valuable tools for the achievement of these objectives.