Evolution of Plant Na+-P-Type ATPases: From Saline Environments to Land Colonization

Soil salinity is one of the major factors obstructing the growth and development of agricultural crops. Eukaryotes have two main transport systems involved in active Na+ removal: cation/H+ antiporters and Na+-P-type ATPases. Key transport proteins, Na+/K+-P-ATPases, are widely distributed among the different taxa families of pumps which are responsible for keeping cytosolic Na+ concentrations below toxic levels. Na+/K+-P-ATPases are considered to be absent in flowering plants. The data presented here are a complete inventory of P-type Na+/K+-P-ATPases in the major branches of the plant kingdom. We also attempt to elucidate the evolution of these important membrane pumps in plants in comparison with other organisms. We were able to observe the gradual replacement of the Na+-binding site to the Ca2+-binding site, starting with cyanobacteria and moving to modern land plants. Our results show that the α-subunit likely evolved from one common ancestor to bacteria, fungi, plants, and mammals, whereas the β-subunit did not evolve in green algae. In conclusion, our results strongly suggest the significant differences in the domain architecture and subunit composition of plant Na+/K+-P-ATPases depending on plant taxa and the salinity of the environment. The obtained data clarified and broadened the current views on the evolution of Na+/K+-P-ATPases. The results of this work would be helpful for further research on P-type ATPase functionality and physiological roles.

Bioelectric characteristics of Chara fragilis (Characeae) cells

For the first time the data on the distribution of the potential (ϕm) and resistance (Rm) in the plasma membrane and cell wall (R0) of Chara fragilis cells were obtained using the Hogg method by the number of C. fragilis cells in standard conditions. The Hogg method allows simultaneous measurement of electrophysiological parameters, such as ϕm and Rm. The stationary values of the membrane potential and resistance varied in a rather wide range: –90...–300 mV and 1.0–32.6 Ohm·m2, respectively. The average values of ϕm were –183.0 ± 4.9 mV, Rm –9.0 ± 1.2 Ohm·m2. Using standard modifiers of membrane transport, the electrogenic activity of the cells was differentiated into two types: K+-channels and H+-membrane pumps. The activation ranges of the K+-inward rectifying channels and K+-outward rectifying channels are –130...–50 and –300...–162 mV, respectively. The cytosolic activity of K+-ions was 61.6 mmol/L. Since in our research, C. fragilis cells were studied for the first time, their electrogenic activity and ionic conductivity were tested using ammonium metavanadate (VO3ˉ) – a proton pump inhibitor and tetraethylammonium (TEA+) – a universal blocker of K+-channels of plasma membranes. Chara fragilis cells can be recommended as a test object for establishing the mechanisms of changes in plasma membrane transport under exogenous stress factors influence.

Overcoming efflux of fluorescent probes for actin imaging in living cells

Actin cytoskeleton is crucial for endocytosis, intracellular trafficking, cell shape maintenance and a wide range of other cellular functions. Recently introduced cell-permeable fluorescent actin probes suffer from poor membrane permeability and stain some cell populations inhomogeneously due to the active efflux by the plasma membrane pumps. We addressed this issue by constructing a series of probes which employ modified rhodamine fluorophores. We found that the best performing probes are based on 6-carboxy-carbopyronine scaffold. These probes show preferential binding to F-actin, do not require efflux pumps inhibitors for staining and can be used for 2D and 3D fluorescence nanoscopy at high nanomolar concentrations without significant cytotoxicity. We demonstrate their excellent performance in multiple organisms and cell types: human cell lines, frog erythrocytes, fruit fly tissues and primary neurons.

Order-disorder transitions of cytoplasmic N-termini in the mechanisms of P-type ATPases

Membrane protein structure and function are modulated via interactions with their lipid environment. This is particularly true for the integral membrane pumps, the P-type ATPases. These ATPases play vital roles...

Membrane Pump Operation Synchronicity (Criticality) in Epidermal Cells: The Possibility of Quantifying the Level of Synchronization

The authors analyze the results of atomic emission spectrometry of hair samples for Al, Cd, Fe, Cr, Cu, Li, Pb, V, and Zn in 952 healthy subjects and 952 liquidators of the Chernobyl nuclear power plant accident. Using correlation analysis (Pearson) of the obtained data, the authors have found pair correlations between metal concentration values. According to the authors, criticality or synchronization (as a particular case of the critical state of the system) can be inherent in all ATP-dependent membrane pumps (P-type) controlling metal-ligand homeostasis in epidermal cells. A quantitative criterion (synchronization index) is proposed to measure the level of criticality (synchronization) in the functioning of membrane ATPases.

On-chip cell sorting by high-speed local-flow control using dual membrane pumps

We achieved high-throughput on-chip sorting of large cells by using on-chip dual membrane pumps integrated with a high-rigidity microfluidic chip. In the case of Euglena gracilis sorting, the throughput was 23 kHz with 92.8% success rate, 95.8% purity, and 90.8% cell viability.