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

Genome-wide identification and analysis of the apple H+-ATPase gene family and its expression against iron deficiency stress

BACKGROUND

Iron (Fe) is indispensable to plants, playing a significant role in life activities such as respiration, chlorophyll biosynthesis, and photosynthetic electron transport. The decrease in pH caused by iron deficiency is related to the activation of H+-ATPase in the root plasma membrane, although the reaction mechanism of this enzyme is not well understood in apples. The H+-ATPase (HA) gene family has been extensively studied in Arabidopsis but is rarely reported in other species.

RESULTS

In this study, 14 HA genes were identified from the apple genome database through whole genome analysis. These apple H+-ATPase (MdHAs) genes were classified into four subsets (I, II, IV, V) based on phylogenetic analysis. Bioinformatics analysis revealed that these genes exhibited diversity in gene structure, chromosomal distribution, conserved motifs, and cis-acting elements. The qRT-PCR analysis revealed that iron deficiency stress significantly induced the upregulation of nine MdHA genes (MdHA5-MdHA14). Furthermore, in the roots of iron deficiency-resistant rootstock variety QZ1 compared to the non-resistant variety QZ2, the expression levels of nine genes (including MdHA1, MdHA6-MdHA13) in QZ2 were significantly lower than those in QZ1. This study lays a foundation for further study on the function of HA gene family.

CONCLUSIONS

These findings suggest that the HA gene family is involved in the apple's response to iron deficiency. This study not only lays the groundwork for future research but also highlights the role of MdHAs in iron stress tolerance.

Molecular insight into auxin signaling and associated network modulating stress responses in rice

Phytohormones are vital regulators of various signaling networks in plants. Among different phytohormones, auxin has been thoroughly studied for its role in regulating plants' growth, development, and stress response. One major function of auxin is modulating the developmental processes in response to environmental cues. Although extensive studies on Arabidopsis have advanced the knowledge of auxin biology, several studies on rice have uncovered key players regulated by auxin that play critical roles in coordinating auxin homeostasis and signaling involved in defense response. The emerging knowledge on auxin biology, auxin-regulated gene expression, and auxin-signaling in rice during various environmental stresses has provided insights into the possible mechanism of rice susceptibility or resistance to different abiotic and biotic stresses. The current review enumerates the possible mechanisms of stress-induced auxin homeostasis in rice. In addition, we provide an overview of the state of knowledge on auxin-mediated defense signaling in rice, highlighting its pivotal role in stress response. In particular, we discuss the auxin pathways and the dynamic regulation in response to biotic and abiotic stress. We highlight the novel findings in the diversity of auxin signaling in the model plant Arabidopsis with an aim to emphasize the need to translate these findings into agronomically and economically important cereals like rice. Addressing the complexity of auxin induction, signaling, and its associated molecular network, an in-depth investigation in rice is required to comprehend auxin-mediated spatial-temporal regulation of developmental processes during stress.

High-light and nutrient interactions drive carbohydrate and proton pump dynamics in Agastache rugosa (Fisch. & C.A.Mey.) Kuntze

Agastache rugosa, a perennial herb native to temperate and subtropical regions, shows remarkable adaptive strategies when exposed to varying light and nutrient conditions in tropical environments. Our study reveals new insights into the crosstalk mechanisms involving carbohydrate homeostasis, biomass allocation, and nutrient acquisition in A. rugosa under different environmental conditions. Treatments were two light levels; HL (high-light, 0% shade) and LL (low-light, 50% shade), and four nutrient rates; NPK1 (40 mg kg-1), NPK2 (80 mg kg-1), NPK3 (120 mg kg-1) and NPK4 (160 mg kg-1). High-light coupled with increasing nutrient levels (HL-NPK3 and HL-NPK4) promoted biomass production via increased carbon assimilation, associated with higher soluble sugar levels and higher phosphorus and potassium uptake mediated by the upregulation of plasma membrane H+-ATPase. Maximum carbohydrate accumulation occurred at high-light and the lowest nutrient levels (HL-NPK1), coinciding with increased nitrogen uptake and the drastically high leaf nitrogen concentration. This response was preceded by the upregulation of acid phosphatase and sucrose phosphate synthase, suggesting a compensatory mechanism to maintain nutrient and carbohydrate reserves for critical metabolic processes. Starch increase was more apparent under low-light and higher nutrient levels (LL-NPK3 and LL-NPK4), relative to invertase downregulation, indicating a shift towards carbohydrate storage rather than utilization. These findings underscore the complex interplay between sugar signaling, nutrient sensing, enzymatic actions, and proton pump activity in modulating plant adaptation to varying environmental conditions. This study also highlights the importance of understanding how non-model medicinal species like A. rugosa reprogram their metabolism and resource allocation in response to environmental changes.

Identification and Analysis of the Plasma Membrane H+-ATPase Gene Family in Cotton and Its Roles in Response to Salt Stress

Plant plasma membrane (PM) H+-ATPase functions as a proton-motive force by exporting cellular protons to establish a transmembrane chemical gradient of H+ ions and an accompanying electrical gradient. These gradients are crucial for plant growth and development and for plant responses to abiotic and biotic stresses. In this study, a comprehensive identification of the PM H+-ATPase gene family was conducted across four cotton species. Specifically, 14 genes were identified in the diploid species Gossypium arboreum and Gossypium raimondii, whereas 39 and 43 genes were identified in the tetraploid species Gossypium hirsutum and Gossypium barbadense, respectively. The characteristics of this gene family were subsequently compared and analyzed using bioinformatics. Chromosomal localization and collinearity analyses elucidated the distribution characteristics of this gene family within the cotton genomes. Gene structure and phylogenetic analyses demonstrated the conservation of this family across cotton species, whereas the examination of cis-acting elements in gene promoters highlighted their involvement in environmental stress and hormone response categories. An expression profile analysis revealed eight genes whose expression was upregulated under salt stress conditions, and quantitative real-time PCR results suggested that the cotton PM H+-ATPase genes may play crucial roles in conferring resistance to salt stress. These findings establish a robust foundation for subsequent investigations into the functions of cotton PM H+-ATPase genes and may offer valuable insights for selecting genes for resistance breeding programs.

The PATROL1 function in roots contributes to the increase in shoot biomass

MAIN CONCLUSION

PATOL1 contributes to increasing biomass not only by effective stomatal movement but also by root meristematic activity. PATROL1 (PROTON ATPase TRANSLOCATION CONTROL 1), a protein with a MUN domain, is involved in the intercellular trafficking of AHA1 H+-ATPase to the plasma membrane in guard cells. This allows for larger stomatal opening and more efficient photosynthesis, leading to increased biomass. Although PATROL1 is expressed not only in stomata but also in other tissues of the shoot and root, the role in other tissues than stomata has not been determined yet. Here, we investigated PATROL1 functions in roots using a loss-of-function mutant and an overexpressor. Cytological observations revealed that root meristematic size was significantly smaller in the mutant resulting in the short primary root. Grafting experiments showed that the shoot biomass of the mutant scion was increased when it grafted onto wild-type or overexpressor rootstocks. Conversely, grafting of the overexpressor scion shoot enhanced the growth of the mutant rootstock. The leaf temperatures of the grafted plants were consistent with those of their respective genotypes, indicating cell-autonomous behavior of stomatal movement and independent roles of PATROL1 in plant growth. Moreover, plasma membrane localization of AHA1 was not altered in root epidermal cells in the patrol1 mutant implying existence of a different mode of PATROL1 action in roots. Thus PATROL1 plays a role in root meristem and contributes to increase shoot biomass.

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.

Identification and characterization of the plasma membrane H+-ATPase genes in Brassica napus and functional analysis of BnHA9 in salt tolerance

As a primary proton pump, plasma membrane (PM) H+-ATPase plays critical roles in regulating plant growth, development, and stress responses. PM H+-ATPases have been well characterized in many plant species. However, no comprehensive study of PM H+-ATPase genes has been performed in Brassica napus (rapeseed). In this study, we identified 32 PM H+-ATPase genes (BnHAs) in the rapeseed genome, and they were distributed on 16 chromosomes. Phylogenetical and gene duplication analyses showed that the BnHA genes were classified into five subfamilies, and the segmental duplication mainly contributed to the expansion of the rapeseed PM H+-ATPase gene family. The conserved domain and subcellular analyses indicated that BnHAs encoded canonical PM H+-ATPase proteins with 14 highly conserved domains and localized on PM. Cis-acting regulatory element and expression pattern analyses indicated that the expression of BnHAs possessed tissue developmental stage specificity. The 25 upstream open reading frames with the canonical initiation codon ATG were predicted in the 5' untranslated regions of 11 BnHA genes and could be used as potential target sites for improving rapeseed traits. Protein interaction analysis showed that BnBRI1.c associated with BnHA2 and BnHA17, indicating that the conserved activity regulation mechanism of BnHAs may be present in rapeseed. BnHA9 overexpression in Arabidopsis enhanced the salt tolerance of the transgenic plants. Thus, our results lay a foundation for further research exploring the biological functions of PM H+-ATPases in rapeseed.

Phosphorus deficiency-induced cell wall pectin demethylesterification enhances cadmium accumulation in roots of Salix caprea

Regions affected by heavy metal contamination frequently encounter phosphorus (P) deficiency. Numerous studies highlight crucial role of P in facilitating cadmium (Cd) accumulation in woody plants. However, the regulatory mechanism by which P affects Cd accumulation in roots remains ambiguous. This study aims to investigate the effects of phosphorus (P) deficiency on Cd accumulation, Cd subcellular distribution, and cell wall components in the roots of Salix caprea under Cd stress. The results revealed that under P deficiency conditions, there was a 35.4% elevation in Cd content in roots, coupled with a 60.1% reduction in Cd content in shoots, compared to the P sufficiency conditions. Under deficient P conditions, the predominant response of roots to Cd exposure was the increased sequestration of Cd in root cell walls. The sequestration of Cd in root cell walls increased from 37.1% under sufficient P conditions to 66.7% under P deficiency, with pectin identified as the primary Cd binding site under both P conditions. Among cell wall components, P deficiency led to a significant 31.7% increase in Cd content within pectin compared to P sufficiency conditions, but did not change the pectin content. Notably, P deficiency significantly increased pectin methylesterase (PME) activity by regulating the expression of PME and PMEI genes, leading to a 10.4% reduction in the degree of pectin methylesterification. This may elucidate the absence of significant changes in pectin content under P deficiency conditions and the concurrent increase in Cd accumulation in pectin. Fourier transform infrared spectroscopy (FTIR) results indicated an increase in carboxyl groups in the root cell walls under P deficiency compared to sufficient P treatment. The results provide deep insights into the mechanisms of higher Cd accumulation in root mediated by P deficiency.

Pb uptake, accumulation, and translocation in plants: Plant physiological, biochemical, and molecular response: A review

Lead (Pb) is a highly toxic contaminant that is ubiquitously present in the ecosystem and poses severe environmental issues, including hazards to soil-plant systems. This review focuses on the uptake, accumulation, and translocation of Pb metallic ions and their toxicological effects on plant morpho-physiological and biochemical attributes. We highlight that the uptake of Pb metal is controlled by cation exchange capacity, pH, size of soil particles, root nature, and other physio-chemical limitations. Pb toxicity obstructs seed germination, root/shoot length, plant growth, and final crop-yield. Pb disrupts the nutrient uptake through roots, alters plasma membrane permeability, and disturbs chloroplast ultrastructure that triggers changes in respiration as well as transpiration activities, creates the reactive oxygen species (ROS), and activates some enzymatic and non-enzymatic antioxidants. Pb also impairs photosynthesis, disrupts water balance and mineral nutrients, changes hormonal status, and alters membrane structure and permeability. This review provides consolidated information concentrating on the current studies associated with Pb-induced oxidative stress and toxic conditions in various plants, highlighting the roles of different antioxidants in plants mitigating Pb-stress. Additionally, we discussed detoxification and tolerance responses in plants by regulating different gene expressions, protein, and glutathione metabolisms to resist Pb-induced phytotoxicity. Overall, various approaches to tackle Pb toxicity have been addressed; the phytoremediation techniques and biochar amendments are economical and eco-friendly remedies for improving Pb-contaminated soils.

Hippuris vulgaris could replace Myriophyllum aquaticum for efficiently removing water phosphorus under low temperature conditions in China

Phytoremediation is widely used for the restoration of aquatic environments. However, the phytoremediation effects and mechanisms of special submerged species of native aquatic plants, especially under low-temperature conditions, are not yet clear. In this study, two typical submerged plants, Myriophyllum aquaticum (M. aquaticum; an exotic species) and Hippuris vulgaris (H. vulgaris; a native species), in China were investigated for their phosphorus (P) removal efficiencies (RE_p) and the related mechanisms of phytophysiology and microorganisms in a low-temperature incubator (10 °C during the day and 2 °C at night). At an initial P level of 0.5 mg L^-1, the two plants exhibited similar RE_p, with the highest values (73.5%-92.1%) observed on days 3-6. After 18 days, the residual P concentration in the water was less than the Grade III limit value (0.2 mg L^-1; GB 3838-2002). However, M. aquaticum had a faster RE_p velocity than H. vulgaris at an initial P level of 3.0 mg L^-1, which was attributed to the mechanisms of plant and its interactions with microorganisms. Compared to the control group, the superoxide dismutase activity of H. vulgaris was significantly increased and its catalase activity was decreased, whereas for that of M. aquaticum was the opposite. Micro region X-ray fluorescence analysis revealed that there may be synergic absorption effects between P, S, and K, and antagonistic absorption action between P and Mn in H. vulgaris. In addition, Acinetobacter, Novosphingobium and Pseudomonas were enriched at 3.0 mg L^-1 P level with these two plants, but Chlorophyta only accumulated with H. vulgaris, respectively. Overall, the native species, H. vulgaris, could replace the exotic M. aquaticum to efficiently remove P from polluted water at low temperatures. These findings provide a theoretical foundation for submerged plants P removal capabilities, and the protection of local ecosystem diversity at low temperatures.

Hydrogen sulfide improves salt tolerance through persulfidation of PMA1 in Arabidopsis

KEY MESSAGE

A new interaction was found between PMA1 and GRF4. H₂S promotes the interaction through persulfidated Cys446 of PMA1. H₂S activates PMA1 to maintain K⁺/Na⁺ homeostasis through persulfidation under salt stress. Plasma membrane H⁺-ATPase (PMA) is a transmembrane transporter responsible for pumping protons, and its contribution to salt resistance is indispensable in plants. Hydrogen sulfide (H₂S), a small signaling gas molecule, plays the important roles in facilitating adaptation of plants to salt stress. However, how H₂S regulates PMA activity remains largely unclear. Here, we show a possible original mechanism for H₂S to regulate PMA activity. PMA1, a predominant member in the PMA family of Arabidopsis, has a non-conservative persulfidated cysteine (Cys) residue (Cys446), which is exposed on the surface of PMA1 and located in cation transporter/ATPase domain. A new interaction of PMA1 and GENERAL REGULATORY FACTOR 4 (GRF4, belongs to the 14-3-3 protein family) was found by chemical crosslinking coupled with mass spectrometry (CXMS) in vivo. H₂S-mediated persulfidation promoted the binding of PMA1 to GRF4. Further studies showed that H₂S enhanced instantaneous H⁺ efflux and maintained K⁺/Na⁺ homeostasis under salt stress. In light of these findings, we suggest that H₂S promotes the binding of PMA1 to GRF4 through persulfidation, and then activating PMA, thus improving the salt tolerance of Arabidopsis.

Interaction Network Construction and Functional Analysis of the Plasma Membrane H+-ATPase in Bangia fuscopurpurea (Rhodophyta)

Salinity is a serious threat to most land plants. Although seaweeds adapt to salty environments, intertidal species experience wide fluctuations in external salinities, including hyper- and hypo-saline stress. Bangia fuscopurpurea is an economic intertidal seaweed with a strong tolerance to hypo-salinity. Until now, the salt stress tolerance mechanism has remained elusive. Our previous study showed that the expression of B. fuscopurpurea plasma membrane H⁺-ATPase (BfPMHA) genes were the most upregulated under hypo-salinity. In this study, we obtained the complete sequence of BfPMHA, traced the relative expression of this BfPMHA gene in B. fuscopurpurea under hypo-salinity, and analyzed the protein structure and properties based on the gene's sequence. The result showed that the expression of BfPMHA in B. fuscopurpurea increased significantly with varying hypo-salinity treatments, and the higher the degree of low salinity stress, the higher the expression level. This BfPMHA had typical PMHA structures with a Cation-N domain, an E1-E2 ATPase domain, a Hydrolase domain, and seven transmembrane domains. In addition, through the membrane system yeast two-hybrid library, three candidate proteins interacting with BfPMHA during hypo-saline stress were screened, fructose-bisphosphate aldolase (BfFBA), glyceraldehyde 3-phosphate dehydrogenase (NADP⁺) (phosphorylating) (BfGAPDH), and manganese superoxide dismutase (BfMnSOD). The three candidates and BfPMHA genes were successfully transferred and overexpressed in a BY4741 yeast strain. All of them significantly enhanced the yeast tolerance to NaCl stress, verifying the function of BfPMHA in salt stress response. This is the first study to report the structure and topological features of PMHA in B. fuscopurpurea and its candidate interaction proteins in response to salt stress.

Involvement of Diamine Oxidase in Modification of Plasma Membrane Proton Pump Activity in Cucumis sativus L. Seedlings under Cadmium Stress

Cucumber (Cucumis sativus L.) is a crop plant being the third most-produced vegetable developed as a new model plant. Heavy metal pollution is a serious global problem that affects crop production. An industrial activity has led to high emissions of Cd into the environment. Plants realize adaptive strategies to diminish the toxic effects of Cd. They can remove excess toxic ions of heavy metals from the cytoplasm to the outside of cells using the metal/proton antiport. The proton gradient needed for the action of the antiporter is generated by the plasma membrane (PM) H⁺-ATPase (EC 3.6.3.14). We have shown that treatment of cucumber plants with Cd stimulated the diamine oxidase (DAO, EC 1.4.3.6) activity in roots. Under cadmium stress, the PM H⁺-ATPase activity also increased in cucumber seedlings. The stimulating effect of Cd on the PM H⁺-ATPase activity and expression of three genes encoding this enzyme (CsHA2, CsHA4, CsHA8) was reduced by aminoguanidine (AG, a DAO inhibitor). Moreover, we have observed that H₂O₂ produced by DAO promotes the formation of NO in the roots of seedlings. The results presented in this work showed that DAO may be an element of the signal transduction pathway, leading to enhanced PM H⁺-ATPase activity under cadmium stress.

Plant Plasma Membrane Proton Pump: One Protein with Multiple Functions

In plants, the plasma membrane proton pump (PM H⁺-ATPase) regulates numerous transport-dependent processes such as growth, development, basic physiology, and adaptation to environmental conditions. This review explores the multifunctionality of this enzyme in plant cells. The abundance of several PM H⁺-ATPase isogenes and their pivotal role in energizing transport in plants have been connected to the phenomena of pleiotropy. The multifunctionality of PM H⁺-ATPase is a focal point of numerous studies unraveling the molecular mechanisms of plant adaptation to adverse environmental conditions. Furthermore, PM H⁺-ATPase is a key element in plant defense mechanisms against pathogen attack; however, it also functions as a target for pathogens that enable plant tissue invasion. Here, we provide an extensive review of the PM H⁺-ATPase as a multitasking protein in plants. We focus on the results of recent studies concerning PM H⁺-ATPase and its role in plant growth, physiology, and pathogenesis.

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.

Nitrate transporter MdNRT2.4 interacts with rhizosphere bacteria to enhance nitrate uptake in apple rootstocks

Plants have developed complex mechanisms to adapt to changing nitrate (NO3-) concentrations and can recruit microbes to boost nitrogen absorption. However, little is known about the relationship between functional genes and the rhizosphere microbiome in NO3- uptake of apple rootstocks. Here, we found that variation in Malus domestica NO3- transporter (MdNRT2.4) expression contributes to nitrate uptake divergence between two apple rootstocks. Overexpression of MdNRT2.4 in apple seedlings significantly improved tolerance to low nitrogen via increasing net NO3- influx at the root surface. However, inhibiting the root plasma membrane H+-ATPase activity abolished NO3- uptake and led to NO3- release, suggesting that MdNRT2.4 encodes an H+-coupled nitrate transporter. Surprisingly, the nitrogen concentration of MdNRT2.4-overexpressing apple seedlings in unsterilized nitrogen-poor soil was higher than that in sterilized nitrogen-poor soil. Using 16S ribosomal RNA gene profiling to characterize the rhizosphere microbiota, we found that MdNRT2.4-overexpressing apple seedlings recruited more bacterial taxa with nitrogen metabolic functions, especially Rhizobiaceae. We isolated a bacterial isolate ARR11 from the apple rhizosphere soil and identified it as Rhizobium. Inoculation with ARR11 improved apple seedling growth in nitrogen-poor soils, compared with uninoculated seedlings. Together, our results highlight the interaction of host plant genes with the rhizosphere microbiota for host plant nutrient uptake.

Silicon-Induced Tolerance against Arsenic Toxicity by Activating Physiological, Anatomical and Biochemical Regulation in Phoenix dactylifera (Date Palm)

Arsenic is a toxic metal abundantly present in agricultural, industrial, and pesticide effluents. To overcome arsenic toxicity and ensure safety for plant growth, silicon (Si) can play a significant role in its mitigation. Here, we aim to investigate the influence of silicon on date palm under arsenic toxicity by screening antioxidants accumulation, hormonal modulation, and the expression profile of abiotic stress-related genes. The results showed that arsenic exposure (As: 1.0 mM) significantly retarded growth attributes (shoot length, root length, fresh weight), reduced photosynthetic pigments, and raised reactive species levels. Contrarily, exogenous application of Si (Na₂SiO₃) to date palm roots strongly influenced stress mitigation by limiting the translocation of arsenic into roots and shoots as compared with the arsenic sole application. Furthermore, an enhanced accumulation of polyphenols (48%) and increased antioxidant activities (POD: 50%, PPO: 75%, GSH: 26.1%, CAT: 51%) resulted in a significant decrease in superoxide anion (O₂^•−: 58%) and lipid peroxidation (MDA: 1.7-fold), in silicon-treated plants, compared with control and arsenic-treated plants. The Si application also reduced the endogenous abscisic acid (ABA: 38%) under normal conditions, and salicylic acid (SA: 52%) and jasmonic acid levels (JA: 62%) under stress conditions as compared with control and arsenic. Interestingly, the genes; zeaxanthin epoxidase (ZEP) and 9-cis-epoxycarotenoid dioxygenase (NCED-1) involved in ABA biosynthesis were upregulated by silicon under arsenic stress. Likewise, Si application also upregulated gene expression of plant plasma membrane ATPase (PMMA-4), aluminum-activated malate transporter (ALMT) responsible for maintaining cellular physiology, stomatal conductance, and short-chain dehydrogenases/reductases (SDR) involved in nutrients translocation. Hence, the study demonstrates the remarkable role of silicon in supporting growth and inducing arsenic tolerance by increasing antioxidant activities and endogenous hormones in date palm. The outcomes of our study can be employed in further studies to better understand arsenic tolerance and decode mechanism.

The molecular mechanism of plasma membrane H+-ATPases in plant responses to abiotic stress

Plasma membrane H⁺-ATPases (PM H⁺-ATPases) are critical proton pumps that export protons from the cytoplasm to the apoplast. The resulting proton gradient and difference in electrical potential energize various secondary active transport events. PM H⁺-ATPases play essential roles in plant growth, development, and stress responses. In this review, we focus on recent studies of the mechanism of PM H⁺-ATPases in response to abiotic stresses in plants, such as salt and high pH, temperature, drought, light, macronutrient deficiency, acidic soil and aluminum stress, as well as heavy metal toxicity. Moreover, we discuss remaining outstanding questions about how PM H⁺-ATPases contribute to abiotic stress responses.