Phosphorylation by CIPK23 regulates the high-affinity Mn transporter NRAMP1 in Arabidopsis.

Manganese (Mn) is essential for plants but is toxic when taken up in excess. To maintain Mn homeostasis, the root Mn transporter natural resistance associated macrophage protein 1 (NRAMP1) cycles from the plasma membrane to endosomes upon phosphorylation. To identify the kinase involved, a split-luciferase screening was carried out between NRAMP1 and kinases of the CIPK family and identified CIPK23 as a partner of NRAMP1.

Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51.

The high-affinity K+ transporter HAK5 from Arabidopsis (Arabidopsis thaliana) is essential for K+ acquisition and plant growth at low micromolar K+ concentrations. Despite its functional relevance in plant nutrition, information about functional domains of HAK5 is scarce. Its activity is enhanced by phosphorylation via the AtCIPK23/AtCBL1-9 complex.

Regulation of Root Nutrient Transporters by CIPK23: 'One Kinase to Rule Them All'.

Protein kinases constitute essential regulatory components in the majority of cellular processes in eukaryotic cells. The CBL-INTERACTING PROTEIN KINASE (CIPK) family of plant protein kinases functions in calcium (Ca2+)-related signaling pathways and is therefore involved in the response to a wide variety of signals in plants. By covalently linking phosphate groups to their target proteins, CIPKs regulate the activity of downstream targets, their localization, their stability and their ability to interact with other proteins.

Arabidopsis K+ transporter HAK5-mediated high-affinity root K+ uptake is regulated by protein kinases CIPK1 and CIPK9.

The high-affinity K+ transporter HAK5 is the major contributor to root K+ uptake from dilute solutions in K+-starved Arabidopsis plants. Its functionality is tightly regulated and its activity is enhanced under K+ starvation by the transcriptional induction of the AtHAK5 gene, and by the activation of the transporter via the AtCBL1-AtCIPK23 complex. In the present study, the 26 members of the Arabidopsis CIPK protein kinase family were screened in yeast for their capacity to activate HAK5-mediated K+ uptake.

High External K Concentrations Impair Pi Nutrition, Induce the Phosphate Starvation Response, and Reduce Arsenic Toxicity in Arabidopsis Plants.

Potassium (K) and phosphorous (Pi) are two of the most important nutrients required by plants and there is an interest in studying how they are acquired. Most studies have focused on the characterization of the mechanisms involved in K and Pi uptake and their distribution within the plants, as well as the regulatory mechanisms involved. Evidence is emerging which points to interactions in the nutrition of different nutrients and to the existence of crosstalk in the signaling cascades regulating their acquisition.

Modulation of K translocation by AKT1 and AtHAK5 in Arabidopsis plants.

Root cells take up K from the soil solution, and a fraction of the absorbed K is translocated to the shoot after being loaded into xylem vessels. K uptake and translocation are spatially separated processes. K uptake occurs in the cortex and epidermis whereas K translocation starts at the stele.

The combination of K deficiency with other environmental stresses: What is the outcome?

Potassium (K ) is a macronutrient known for its high mobility and positive charge, which allows efficient and fast control of the electrical balance and osmotic potential in plant cells. Such features allow K to remarkably contribute to plant stress adaptation. Some agricultural lands are deficient in K , imposing a stress that reduces crop yield and makes fertilization a common practice.

Tolerance to Stress Combination in Tomato Plants: New Insights in the Protective Role of Melatonin.

Abiotic stresses such as drought, heat or salinity are major causes of yield loss worldwide. Recent studies have revealed that the acclimation of plants to a combination of different environmental stresses is unique and therefore cannot be directly deduced from studying the response of plants to each of the different stresses applied individually. The efficient detoxification of reactive oxygen species (ROS) is thought to play a key role in enhancing the tolerance of plants to abiotic stresses.

Pharmacological and gene regulation properties point to the SlHAK5 K transporter as a system for high-affinity Cs uptake in tomato plants.

Potassium (K ) and cesium (Cs ) are chemically similar but while K is an essential nutrient, Cs can be toxic for living organisms, plants included. Two different situations could lead to problems derived from the presence of Cs in agricultural systems: (1) presence of Cs at high concentrations that could produce toxic effects on plants, (2) presence of micromolar concentrations of radiocesium, which can be accumulated in the plant and affect animal and human health through the food chain. While K uptake has been well described in tomato plants, information on molecular mechanisms involved in Cs accumulation in this species is absent.

How DELLAs contribute to control potassium uptake under conditions of potassium scarcity? Hypotheses and uncertainties.

Maintenance of the inward transport of potassium (K) by roots is a critical step to ensure K-nutrition for all plant tissues. When plants are grown at low external K concentrations a strong enhancement of the activity of the AtHAK5 transporter takes place. In a recent work, we observed that the gai-1 mutant of Arabidopsis thaliana, which bears an altered function version of a DELLA regulatory protein, displays reduced accumulation of AtHAK5 transcripts and reduced uptake of Rubidium, an analog for K.

NO , PO and SO deprivation reduced LKT1-mediated low-affinity K uptake and SKOR-mediated K translocation in tomato and Arabidopsis plants.

Regulation of essential macronutrients acquisition by plants in response to their availability is a key process for plant adaptation to changing environments. Here we show in tomato and Arabidopsis plants that when they are subjected to NO , PO and SO deprivation, low-affinity K uptake and K translocation to the shoot are reduced. In parallel, these nutritional deficiencies produce reductions in the messenger levels of the genes encoding the main systems for low-affinity K uptake and K translocation, i.

Uneven HAK/KUP/KT Protein Diversity Among Angiosperms: Species Distribution and Perspectives.

HAK/KUP/KT K(+) transporters have been widely associated with K(+) transport across membranes in bacteria, fungi, and plants. Indeed some members of the plant HAK/KUP/KT family contribute to root K(+) uptake, notably at low external concentrations. Besides such role in acquisition, several studies carried out in Arabidopsis have shown that other members are also involved in developmental processes.

The CBL-Interacting Protein Kinase CIPK23 Regulates HAK5-Mediated High-Affinity K+ Uptake in Arabidopsis Roots.

Plant growth and development requires efficient acquisition of essential elements. Potassium (K(+)) is an important macronutrient present in the soil solution at a wide range of concentrations. Regulation of the K(+) uptake systems in the roots is essential to secure K(+) supply.

High Ca(2+) reverts the repression of high-affinity K(+) uptake produced by Na(+) in Solanum lycopersycum L. (var. microtom) plants.

Potassium (K(+)) is an essential nutrient for plants which is acquired by plant roots through the operation of specific transport systems. Abiotic stress conditions such as salinity impair K(+) nutrition because, in addition to other effects, high salt concentrations in the solution bathing the roots inhibit K(+) uptake systems. This detrimental effect of salinity is exacerbated when external K(+) is very low and the only system capable of mediating K(+) uptake is one with high-affinity for K(+), as that mediated by transporters of the HAK5 type.

The F130S point mutation in the Arabidopsis high-affinity K(+) transporter AtHAK5 increases K(+) over Na(+) and Cs(+) selectivity and confers Na(+) and Cs(+) tolerance to yeast under heterologous expression.

Potassium (K(+)) is an essential macronutrient required for plant growth, development and high yield production of crops. Members of group I of the KT/HAK/KUP family of transporters, such as HAK5, are key components for K(+) acquisition by plant roots at low external K(+) concentrations. Certain abiotic stress conditions such as salinity or Cs(+)-polluted soils may jeopardize plant K(+) nutrition because HAK5-mediated K(+) transport is inhibited by Na(+) and Cs(+).

A low K+ signal is required for functional high-affinity K+ uptake through HAK5 transporters.

The high-affinity K(+) transporter HAK5 is a key system for root K(+) uptake and, under very low external K(+), the only one capable of supplying K(+) to the plant. Functional HAK5-mediated K(+) uptake should be tightly regulated for plant adaptation to different environmental conditions. Thus, it has been described that the gene encoding the transporter is transcriptionally regulated, being highly induced under K(+) limitation.