Overexpression of a Plasma Membrane H+-ATPase Gene OSA1 Stimulates the Uptake of Primary Macronutrients in Rice Roots.

Plasma membrane (PM) H+-ATPase is a master enzyme involved in various plant physiological processes, such as stomatal movements in leaves and nutrient uptake and transport in roots. Overexpression of Oryza sativa PM H+-ATPase 1 (OSA1) has been known to increase NH4+ uptake in rice roots. Although electrophysiological and pharmacological experiments have shown that the transport of many substances is dependent on the proton motive force provided by PM H+-ATPase, the exact role of PM H+-ATPase on the uptake of nutrients in plant roots, especially for the primary macronutrients N, P, and K, is still largely unknown. Here, we used OSA1 overexpression lines (OSA1-oxs) and gene-knockout osa1 mutants to investigate the effect of modulation of PM H+-ATPase on the absorption of N, P, and K nutrients through the use of a nutrient-exhaustive method and noninvasive microtest technology (NMT) in rice roots. Our results showed that under different concentrations of P and K, the uptake rates of P and K were enhanced in OSA1-oxs; by contrast, the uptake rates of P and K were significantly reduced in roots of osa1 mutants when compared with wild-type. In addition, the net influx rates of NH4+ and K+, as well as the efflux rate of H+, were enhanced in OSA1-oxs and suppressed in osa1 mutants under low concentration conditions. In summary, this study indicated that overexpression of OSA1 stimulated the uptake rate of N, P, and K and promoted flux rates of cations (i.e., H+, NH4+, and K+) in rice roots. These results may provide a novel insight into improving the coordinated utilization of macronutrients in crop plants.

Overexpression of rice aquaporin OsPIP1;2 improves yield by enhancing mesophyll CO2 conductance and phloem sucrose transport.

Aquaporins are involved in CO2 transport from the leaf intercellular air space to the chloroplast, which contributes to CO2 assimilation. However, the mechanism of CO2 transport by rice (Oryza sativa L.) aquaporins is unknown. Here, we investigated the function of the aquaporin OsPIP1;2 in CO2 diffusion-associated photosynthesis and phloem sucrose transport. Moreover, the grain yield of rice lines overexpressing OsPIP1;2 was determined. OsPIP1;2 was localized to the plasma membrane and the relative expression of OsPIP1;2 was approximately 5-fold higher in leaves in the presence of an elevated CO2 concentration. Overexpression of OsPIP1;2 increased mesophyll conductance by approximately 150% compared with wild-type (WT) rice. The OsPIP1;2-overexpressing lines had higher biomass than the WT, possibly due to increased phloem sucrose transport. In addition, the grain yield of OsPIP1;2-overexpressing lines was approximately 25% higher than that of the WT in three-season field experiments, due to the increased numbers of effective tillers and spikelets per panicle. Our results suggest that OsPIP1;2 modulates rice growth and grain yield by facilitating leaf CO2 diffusion, which increases both the net CO2 assimilation rate and sucrose transport.

Plasma membrane H+-ATPases in mineral nutrition and crop improvement.

Plasma membrane H+-ATPases (PMAs) pump H+ out of the cytoplasm by consuming ATP to generate a membrane potential and proton motive force for the transmembrane transport of nutrients into and out of plant cells. PMAs are involved in nutrient acquisition by regulating root growth, nutrient uptake, and translocation, as well as the establishment of symbiosis with arbuscular mycorrhizas. Under nutrient stresses, PMAs are activated to pump more H+ and promote organic anion excretion, thus improving nutrient availability in the rhizosphere. Herein we review recent progress in the physiological functions and the underlying molecular mechanisms of PMAs in the efficient acquisition and utilization of various nutrients in plants. We also discuss perspectives for the application of PMAs in improving crop production and quality.

Protease Inhibitor-Dependent Inhibition of Light-Induced Stomatal Opening.

Stomata in the epidermis of plants play essential roles in the regulation of photosynthesis and transpiration. Stomata open in response to blue light (BL) by phosphorylation-dependent activation of the plasma membrane (PM) H+-ATPase in guard cells. Under water stress, the plant hormone abscisic acid (ABA) promotes stomatal closure via the ABA-signaling pathway to reduce water loss. We established a chemical screening method to identify compounds that affect stomatal movements in Commelina benghalensis. We performed chemical screening using a protease inhibitor (PI) library of 130 inhibitors to identify inhibitors of stomatal movement. We discovered 17 PIs that inhibited light-induced stomatal opening by more than 50%. Further analysis of the top three inhibitors (PI1, PI2, and PI3; inhibitors of ubiquitin-specific protease 1, membrane type-1 matrix metalloproteinase, and matrix metalloproteinase-2, respectively) revealed that these inhibitors suppressed BL-induced phosphorylation of the PM H+-ATPase but had no effect on the activity of phototropins or ABA-dependent responses. The results suggest that these PIs suppress BL-induced stomatal opening at least in part by inhibiting PM H+-ATPase activity but not the ABA-signaling pathway. The targets of PI1, PI2, and PI3 were predicted by bioinformatics analyses, which provided insight into factors involved in BL-induced stomatal opening.

Molecular basis of plasma membrane H+-ATPase function and potential application in the agricultural production.

Increase of crop yield is always the desired goal, manipulation of genes in relation to plant growth is a shortcut to promote crop yield. The plasma membrane (PM) H+-ATPase is the plant master enzyme; the energy yielded by ATP hydrolysis pumps H+ out of cells, establishes the membrane potential, maintains pH homeostasis and provides the proton-motive force required for transmembrane transport of many materials. PM H+-ATPase is involved in root nutrient uptake, epidermal stomatal opening, phloem sucrose loading and unloading, and hypocotyl cell elongation. In this review, we summarize the recent progresses in roles of PM H+-ATPase in nutrient uptake and light-induced stomatal opening and discuss the pivotal role of PM H+-ATPase in crop yield improvement and its potential application in agricultural production by modulating the expression of PM H+-ATPase in crops.

SIMULATION AND MEASUREMENT OF EXTERNAL ELECTROMAGNETIC ENVIRONMENT OF TOKAMAK DEVICE.

Magnetic confinement nuclear fusion is an important way to realize controllable nuclear fusion. Due to the large current and complicated coil arrangement, there is a complicated electromagnetic environment around the fusion device. In this paper, the B-dot sensor is used to measure the magnetic field, the D-dot sensor is used to measure the electric field, the MAXWELL electromagnetic simulation software is used to simulate the electromagnetic field strength; the simulation and measurement of the spherical Tokamak SUNIST device and the measurement of MARX generator are carried out, then we give corresponding electromagnetic protection suggestions.

Plasma membrane H+-ATPase overexpression increases rice yield via simultaneous enhancement of nutrient uptake and photosynthesis.

Nitrogen (N) and carbon (C) are essential elements for plant growth and crop yield. Thus, improved N and C utilisation contributes to agricultural productivity and reduces the need for fertilisation. In the present study, we find that overexpression of a single rice gene, Oryza sativa plasma membrane (PM) H+-ATPase 1 (OSA1), facilitates ammonium absorption and assimilation in roots and enhanced light-induced stomatal opening with higher photosynthesis rate in leaves. As a result, OSA1 overexpression in rice plants causes a 33% increase in grain yield and a 46% increase in N use efficiency overall. As PM H+-ATPase is highly conserved in plants, these findings indicate that the manipulation of PM H+-ATPase could cooperatively improve N and C utilisation, potentially providing a vital tool for food security and sustainable agriculture.

Potassium alleviates ammonium toxicity in rice by reducing its uptake through activation of plasma membrane H+-ATPase to enhance proton extrusion.

Potassium (K+) has been reported to alleviate ammonium (NH4+) toxicity in rice through some underlying mechanisms, but it still not clear. In addition, K+ is an important cation for activation of plasma membrane (PM) H+-ATPase activity. Here, we hypothesized that K+ alleviated NH4+ toxicity by mediating PM H+-ATPase function in rice root. In this study, rice plants were cultivated in hydroponic solution with various concentrations of K+ and NH4+. By concurrently supplying K+ with NH4+ or re-supplying K+ after NH4+ toxicity, we found that high K+ concentration reduced the NH4+ uptake rate, enhanced the H+ extrusion rate by the roots, and alleviated rice NH4+ toxicity. The gene expression levels of PM H+-ATPase members (OsA1, 3, 7, 8, and 9) were upregulated by application of increasing concentrations of K+ under NH4+ toxicity. The PM H+-ATPase activity and protein expression in rice roots were also enhanced. Furthermore, the enhancement of PM H+-ATPase activity by a specific stimulator (fusicoccin) rescued rice seedlings from NH4+ toxicity. Taken together, these results indicate that K+ can alleviate NH4+ toxicity, possibly by activating PM H+-ATPase to extrude more H+ and inhibit NH4+ uptake by root. Our results may enhance understanding of the strategy of applying K+ fertilizer to mitigate crop NH4+ toxicity in agriculture.