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Ethylene is a major plant hormone that regulates plant growth, development, and defense responses to biotic and abiotic stresses. The major pieces of the ethylene signaling pathway have been put together, although several details still need to be elucidated. For instance, the phosphorylation and dephosphorylation processes controlling the ethylene responses are poorly understood and need to be further explored. The type 2A protein phosphatase (PP2A) was suggested to play an important role in the regulation of ethylene biosynthesis, where the A1 subunit of PP2A was shown to be involved in the regulation of the rate-limiting enzyme of the ethylene biosynthetic pathway. However, whether other subunits of PP2A play roles in the ethylene signal transduction pathway is yet to be answered. In this study, we demonstrate that a B subunit, PP2A-B'ζ, positively regulates plant germination and seedling development, as a pp2a-b'ζ mutant is very sensitive to ethylene treatment. Furthermore, PP2A-B'ζ interacts with and stabilizes the kinase CTR1 (Constitutive Triple Response 1), a key enzyme in the ethylene signal transduction pathway, and like CTR1, PP2A-B'ζ negatively regulates ethylene signaling in plants., (Copyright © 2021 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Abiotic stresses are major threats to agricultural production. Drought and salinity as two of the major abiotic stresses cause billions of losses in agricultural productivity worldwide each year. Thus, it is imperative to make crops more tolerant. Overexpression of AVP1 or PP2A-C5 was previously shown to increase drought and salt stress tolerance, respectively, in transgenic plants. In this study, the hypothesis that co-overexpression of AVP1 and PP2A-C5 would combine their respective benefits and further improve salt tolerance was tested. The two genes were inserted into the same T-DNA region of the binary vector and then introduced into the Arabidopsis genome through Agrobacterium-mediated transformation. Transgenic Arabidopsis plants expressing both AVP1 and PP2A-C5 at relatively high levels were identified and analyzed. These plants displayed enhanced tolerance to NaCl compared to either AVP1 or PP2A-C5 overexpressing plants. They also showed tolerance to other stresses such as KNO 3 and LiCl at harmful concentrations, drought, and phosphorus deficiency at comparable levels with either AVP1 or PP2A-C5 overexpressing plants. This study demonstrates that introducing multiple genes in single T-DNA region is an effective approach to create transgenic plants with enhanced tolerance to multiple stresses., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

Sumoylation is one of the post translational modifications, which affects cellular processes in plants through conjugation of small ubiquitin like modifier (SUMO) to target substrate proteins. Response to various abiotic environmental stresses is one of the major cellular functions regulated by SUMO conjugation. SIZ1 is a SUMO E3 ligase, facilitating a vital step in the sumoylation pathway. In this report, it is demonstrated that over-expression of the rice gene OsSIZ1 in Arabidopsis leads to increased tolerance to multiple abiotic stresses. For example, OsSIZ1-overexpressing plants exhibited enhanced tolerance to salt, drought, and heat stresses, and generated greater seed yields under a variety of stress conditions. Furthermore, OsSIZ1-overexpressing plants were able to exclude sodium ions more efficiently when grown in saline soils and accumulate higher potassium ions as compared to wild-type plants. Further analysis revealed that OsSIZ1-overexpressing plants expressed higher transcript levels of P5CS, a gene involved in the biosynthesis of proline, under both salt and drought stress conditions. Therefore, proline here is acting as an osmoprotectant to alleviate damages caused by drought and salt stresses. These results demonstrate that the rice gene OsSIZ1 has a great potential to be used for improving crop's tolerance to several abiotic stresses., Competing Interests: The authors have declared that no competing interests exist.

Phytoene synthase (PSY) is the crucial plastidial enzyme in the carotenoid biosynthetic pathway. However, its post-translational regulation remains elusive. Likewise, Clp protease constitutes a central part of the plastid protease network, but its substrates for degradation are not well known. In this study, we report that PSY is a substrate of the Clp protease. PSY was uncovered to physically interact with various Clp protease subunits (i.e., ClpS1, ClpC1, and ClpD). High levels of PSY and several other carotenogenic enzyme proteins overaccumulate in the clpc1, clpp4, and clpr1-2 mutants. The overaccumulated PSY was found to be partially enzymatically active. Impairment of Clp activity in clpc1 results in a reduced rate of PSY protein turnover, further supporting the role of Clp protease in degrading PSY protein. On the other hand, the ORANGE (OR) protein, a major post-translational regulator of PSY with holdase chaperone activity, enhances PSY protein stability and increases the enzymatically active proportion of PSY in clpc1, counterbalancing Clp-mediated proteolysis in maintaining PSY protein homeostasis. Collectively, these findings provide novel insights into the quality control of plastid-localized proteins and establish a hitherto unidentified post-translational regulatory mechanism of carotenogenic enzymes in modulating carotenoid biosynthesis in plants., (Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.)

Protein phosphatase 2A (PP2A) was shown to play important roles in biotic and abiotic stress signaling pathways in plants. PP2A is made of 3 subunits: a scaffolding subunit A, a regulatory subunit B, and a catalytic subunit C. It is believed that the B subunit recognizes specific substrates and the C subunit directly acts on the selected substrates, whereas the A subunit brings a B subunit and a C subunit together to form a specific PP2A holoenzyme. Because there are multiple isoforms for each PP2A subunit, there could be hundreds of novel PP2A holoenzymes in plants. For an example, there are 3 A subunits, 17 B subunits, and 5 C subunits in Arabidopsis, which could form 255 different PP2A holoenzymes. Understanding the roles of these PP2A holoenzymes in various signaling pathways is a challenging task. In a recent study, 1 we discovered that PP2A-C5, the catalytic subunit 5 of PP2A, plays an important role in salt tolerance in Arabidopsis. We found that a knockout mutant of PP2A-C5 (i.e. pp2a-c5-1) was very sensitive to salt treatments, whereas PP2A-C5-overexpressing plants were more tolerant to salt stresses. Genetic analyses between pp2a-c5-1 and Salt-Overly-Sensitive (SOS) mutants indicated that PP2A-C5 does not function in the same pathway as SOS genes. Using yeast 2-hybrid analysis, we found that PP2A-C5 interacts with several vacuolar membrane bound chloride channel proteins. We hypothesize that these vacuolar chloride channel proteins might be PP2A-C5's substrates in vivo, and the action of PP2A-C5 on these channel proteins could increase or activate their activities, thereby result in accumulation of the chloride and sodium contents in vacuoles, leading to increased salt tolerance in plants.

Protein phosphatase 2A (PP2A) is an enzyme consisting of three subunits: a scaffolding A subunit, a regulatory B subunit and a catalytic C subunit. PP2As were shown to play diverse roles in eukaryotes. In this study, the function of the Arabidopsis PP2A-C5 gene that encodes the catalytic subunit 5 of PP2A was studied using both loss-of-function and gain-of-function analyses. Loss-of-function mutant pp2a-c5-1 displayed more impaired growth during root and shoot development, whereas overexpression of PP2A-C5 conferred better root and shoot growth under different salt treatments, indicating that PP2A-C5 plays an important role in plant growth under salt conditions. Double knockout mutants of pp2a-c5-1 and salt overly sensitive (sos) mutants sos1-1, sos2-2 or sos3-1 showed additive sensitivity to NaCl, indicating that PP2A-C5 functions in a pathway different from the SOS signalling pathway. Using yeast two-hybrid analysis, four vacuolar membrane chloride channel (CLC) proteins, AtCLCa, AtCLCb, AtCLCc and AtCLCg, were found to interact with PP2A-C5. Moreover, overexpression of AtCLCc leads to increased salt tolerance and Cl - accumulation in transgenic Arabidopsis plants. These data indicate that PP2A-C5-mediated better growth under salt conditions might involve up-regulation of CLC activities on vacuolar membranes and that PP2A-C5 could be used for improving salt tolerance in crops., (© 2016 The Authors Plant, Cell & Environment Published by John Wiley & Sons Ltd.)

The Arabidopsis gene AtNHX1 encodes a vacuolar membrane-bound sodium/proton (Na(+)/H(+)) antiporter that transports Na(+) into the vacuole and exports H(+) into the cytoplasm. The Arabidopsis gene SOS1 encodes a plasma membrane-bound Na(+)/H(+) antiporter that exports Na(+) to the extracellular space and imports H(+) into the plant cell. Plants rely on these enzymes either to keep Na(+) out of the cell or to sequester Na(+) into vacuoles to avoid the toxic level of Na(+) in the cytoplasm. Overexpression of AtNHX1 or SOS1 could improve salt tolerance in transgenic plants, but the improved salt tolerance is limited. NaCl at concentration >200 mM would kill AtNHX1-overexpressing or SOS1-overexpressing plants. Here it is shown that co-overexpressing AtNHX1 and SOS1 could further improve salt tolerance in transgenic Arabidopsis plants, making transgenic Arabidopsis able to tolerate up to 250 mM NaCl treatment. Furthermore, co-overexpression of AtNHX1 and SOS1 could significantly reduce yield loss caused by the combined stresses of heat and salt, confirming the hypothesis that stacked overexpression of two genes could substantially improve tolerance against multiple stresses. This research serves as a proof of concept for improving salt tolerance in other plants including crops., (© The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.)

The caseinolytic peptidase (Clp) core proteins are essential for plant growth and development, especially for chloroplast function. Antisense or overexpression of ClpP4, which is one of the Clp core subunits, causes chlorotic phenotypes in Arabidopsis. An E3 ligase gene, AtCHIP, has previously been found to ubiquitylate ClpP4 in vitro. ClpP4 antisense and overexpressing plants that also overexpressed AtCHIP were constructed to explore the effect of AtCHIP on ClpP4. Overexpression of AtCHIP was found to rescue the chlorotic phenotypes of both ClpP4 antisense and overexpressing plants. The unbalanced levels of Clp core proteins in ClpP4 antisense and overexpressing plants with overexpression of AtCHIP were similar to wild-type levels, suggesting that AtCHIP regulates Clp core proteins. The results also show that AtCHIP can interact with ClpP3 and ClpP5 in yeast and ubiquitylate ClpP3 and ClpP5 in vitro. This suggests that AtCHIP is directly related to ClpP3 and ClpP5. Given these results, the inference is that through selective degradation of Clp subunits, AtCHIP could positively regulate homeostasis of Clp proteolytic subunits and maximize the production of functional chloroplasts. Similar results were obtained from transgenic tobacco plants, suggesting that regulation of the Clp protease by AtCHIP is conserved., (© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

AtPTPA is a critical regulator for the holoenzyme assembling of protein phosphatase 2A (PP2A) in Arabidopsis. Characterization of AtPTPA improves our understanding of the function and regulation of PP2A in eukaryotes. Further analysis of AtPTPA-overexpressing plants indicates that AtPTPA increases PP2A activity by promoting PP2A's AC dimer formation, thereby holoenzyme assembling. Plant hormone abscisic acid (ABA) reduces PP2A enzyme activity by negatively affects PP2A's AC dimer formation. Therefore, AtPTPA is a positive factor that promotes PP2A holoenzyme assembly, and ABA is a negative factor that prevents PP2A holoenzyme assembly.

PROTEIN PHOSPHATASE 2A (PP2A) is a major group of serine/threonine protein phosphatases in eukaryotes. It is composed of three subunits: scaffolding subunit A, regulatory subunit B, and catalytic subunit C. Assembly of the PP2A holoenzyme in Arabidopsis (Arabidopsis thaliana) depends on Arabidopsis PHOSPHOTYROSYL PHOSPHATASE ACTIVATOR (AtPTPA). Reduced expression of AtPTPA leads to severe defects in plant development, altered responses to abscisic acid, ethylene, and sodium chloride, and decreased PP2A activity. In particular, AtPTPA deficiency leads to decreased methylation in PP2A-C subunits (PP2Ac). Complete loss of PP2Ac methylation in the suppressor of brassinosteroid insensitive1 mutant leads to 30% reduction of PP2A activity, suggesting that PP2A with a methylated C subunit is more active than PP2A with an unmethylated C subunit. Like AtPTPA, PP2A-A subunits are also required for PP2Ac methylation. The interaction between AtPTPA and PP2Ac is A subunit dependent. In addition, AtPTPA deficiency leads to reduced interactions of B subunits with C subunits, resulting in reduced functional PP2A holoenzyme formation. Thus, AtPTPA is a critical factor for committing the subunit A/subunit C dimer toward PP2A heterotrimer formation., (© 2014 American Society of Plant Biologists. All Rights Reserved.)

TAP46 is a protein phosphatase2A (PP2A)-associated protein that regulates PP2A activity in Arabidopsis (Arabidopsis thaliana). To study how PP2A is involved in abscisic acid (ABA) signaling in plants, we studied the function of TAP46 in ABA-regulated seed maturation and seedling development. Expression of TAP46 coincides with the action of ABA in developing seeds and during seed germination, and the TAP46 transcript reaches to the highest level in mature seeds. Real-time polymerase chain reaction analysis indicates that external ABA can increase TAP46 transcript level transiently during seed germination. Overexpression of TAP46 increases plant sensitivity to ABA, while tap46 knockdown mutants are less sensitive to ABA during seed germination, suggesting that TAP46 functions positively in ABA signaling. Overexpression of TAP46 also leads to lower PP2A activity, while tap46-1 knockdown mutant displays higher PP2A activity, suggesting that TAP46 negatively regulates PP2A activity in Arabidopsis. Both TAP46 and PP2A interact with the ABA-regulated transcription factor ABA INSENSITIVE5 (ABI5) in vivo, and TAP46's binding to ABI5 can stabilize ABI5. Furthermore, TAP46's binding to the phosphorylated ABI5 may prevent PP2A or PP2A-like protein phosphatases from removing the phosphate from ABI5, thereby maintaining ABI5 in its active form. Overexpression of TAP46 and inhibition of activities of PP2A or PP2A-like protein phosphatases can increase transcript levels of several ABI5-regulated genes, suggesting that TAP46 is a positive factor in the ABA-regulated gene expression in Arabidopsis.

The Arabidopsis gene AVP1 encodes a vacuolar pyrophosphatase that functions as a proton pump on the vacuolar membrane. Overexpression of AVP1 in Arabidopsis, tomato and rice enhances plant performance under salt and drought stress conditions, because up-regulation of the type I H+-PPase from Arabidopsis may result in a higher proton electrochemical gradient, which facilitates enhanced sequestering of ions and sugars into the vacuole, reducing water potential and resulting in increased drought- and salt tolerance when compared to wild-type plants. Furthermore, overexpression of AVP1 stimulates auxin transport in the root system and leads to larger root systems, which helps transgenic plants absorb water more efficiently under drought conditions. Using the same approach, AVP1-expressing cotton plants were created and tested for their performance under high-salt and reduced irrigation conditions. The AVP1-expressing cotton plants showed more vigorous growth than wild-type plants in the presence of 200 mM NaCl under hydroponic growth conditions. The soil-grown AVP1-expressing cotton plants also displayed significantly improved tolerance to both drought and salt stresses in greenhouse conditions. Furthermore, the fibre yield of AVP1-expressing cotton plants is at least 20% higher than that of wild-type plants under dry-land conditions in the field. This research indicates that AVP1 has the potential to be used for improving crop's drought- and salt tolerance in areas where water and salinity are limiting factors for agricultural productivity., (© 2010 Society for Experimental Biology and Blackwell Publishing Ltd.)

The Arabidopsis ankyrin-repeat containing protein 2A (AKR2A) was shown to be an essential molecular chaperone for the peroxisomal membrane-bound ascorbate peroxidase 3 (APX3), because the biogenesis of APX3 depends on the function of AKR2A in plant cells. AKR2A binds specifically to a sequence in APX3 that is made up of a transmembrane domain followed by a few positively charged amino acid residues; this sequence is named as AKR2A-binding sequence or ABS. Interestingly, a sequence in the chloroplast outer envelope protein 7 (OEP7) shares similar features to ABS and is able to bind specifically to AKR2A, suggesting a possibility that proteins with a sequence similar to ABS could bind to AKR2A and they are all likely ligand proteins of AKR2A. This hypothesis was supported by analyzing 5 additional proteins that contain sequences similar to ABS using the yeast two-hybrid technique. A preliminary survey in the Arabidopsis genome indicates that there are at least 500 genes encoding proteins that contain sequences similar to ABS, which raises interesting questions: are these proteins AKR2A's ligand proteins and does AKR2A play a critical role in the biogenesis of these proteins in plants?

The Arabidopsis E3 ligase AtCHIP was found to interact with FtsH1, a subunit of the chloroplast FtsH protease complex. FtsH1 can be ubiquitylated by AtCHIP in vitro, and the steady-state level of FtsH1 is reduced in AtCHIP-over-expressing plants under high-intensity light conditions, suggesting that the ubiquitylation of FtsH1 by AtCHIP might lead to the degradation of FtsH1 in vivo. Furthermore, the steady-state level of another subunit of the chloroplast FtsH protease complex, FtsH2, is also reduced in AtCHIP-over-expressing plants under high-intensity light conditions, and FtsH2 interacts physically with AtCHIP in vivo, suggesting the possibility that FtsH2 is also a substrate protein for AtCHIP in plant cells. A substrate of FtsH protease in vivo, the photosystem II reaction center protein D1, is not efficiently removed by FtsH in AtCHIP-over-expressing plants under high-intensity light conditions, supporting the assumption that FtsH subunits are substrates of AtCHIP in vivo, and that AtCHIP over-expression may lead to a reduced level of FtsH in chloroplasts. AtCHIP interacts with cytosolic Hsp70 and the precursors of FtsH1 and FtsH2 in the cytoplasm, and Hsp70 also interacts with FtsH1, and these protein-protein interactions appear to be increased under high-intensity light conditions, suggesting that Hsp70 might be partly responsible for the increased degradation of the substrates of Hsp70, such as FtsH1 and FtsH2, in AtCHIP-over-expressing plants under high-intensity light conditions. Therefore, AtCHIP, together with Hsp70, may play an important role in protein quality control in chloroplasts.

CHIP proteins are E3 ubiquitin ligases that promote degradation of Hsp70 and Hsp90 substrate proteins through the 26S proteasome in animal systems. A CHIP-like protein in Arabidopsis, AtCHIP, also has E3 ubiquitin ligase activity and has important roles to play under conditions of abiotic stress. In an effort to study the mode of action of AtCHIP in plant cells, proteins that physically interact with it were identified. Like its animal orthologs, AtCHIP interacts with a unique class of ubiquitin-conjugating enzymes (UBC or E2) that belongs to the stress-inducible UBC4/5 class in yeast. AtCHIP also interacts with other proteins, including an A subunit of protein phosphatase 2A (PP2A). This PP2A subunit appears to be a substrate of AtCHIP, because it can be ubiquitylated by AtCHIP in vitro and because the activity of PP2A is increased in AtCHIP-overexpressing plants in the dark or under low-temperature conditions. Unlike the rcn1 mutant, that has reduced PP2A activity due to a mutation in one of the A subunit genes of PP2A, AtCHIP-overexpressing plants are more sensitive to ABA treatment. Since PP2A was previously shown to be involved in low-temperature responses in plants, the low-temperature-sensitive phenotype observed in AtCHIP-overexpressing plants might be partly due to the change in PP2A activity. These data suggest that the E3 ubiquitin ligase AtCHIP may function upstream of PP2A in stress-responsive signal transduction pathways under conditions of low temperature or in the dark.

Ascorbate peroxidase (APX) exists as several isoforms that are found in various compartments in plant cells. The cytosolic and chloroplast APXs appear to play important roles in antioxidation metabolism in plant cells, yet the function of peroxisomal APX is not well studied. In this study, the localization of a putative peroxisomal membrane-bound ascorbate peroxidase, APX3 from Arabidopsis, was confirmed by studying the green fluorescent protein (GFP)-APX3 fusion protein in transgenic plants. GFP-APX3 was found to co-localize with a reporter protein that was targeted to peroxisomes by the peroxisomal targeting signal 1. The function of APX3 in Arabidopsis was investigated by analysing an APX3 knockout mutant under normal and several stress conditions. It was found that loss of function in APX3 does not affect Arabidopsis growth and development, suggesting that APX3 may not be an important antioxidant enzyme in Arabidopsis, at least under the conditions that were tested, or the function of APX3 could be compensated by other antioxidant enzymes in plant cells.

Drought and salinity are two major limiting factors in crop productivity. One way to reduce crop loss caused by drought and salinity is to increase the solute concentration in the vacuoles of plant cells. The accumulation of sodium ions inside the vacuoles provides a 2-fold advantage: (i) reducing the toxic levels of sodium in cytosol; and (ii) increasing the vacuolar osmotic potential with the concomitant generation of a more negative water potential that favors water uptake by the cell and better tissue water retention under high soil salinity. The success of this approach was demonstrated in several plants, where the overexpression of the Arabidopsis gene AtNHX1 that encodes a vacuolar sodium/proton antiporter resulted in higher plant salt tolerance. Overexpression of AtNHX1 increases sodium uptake in vacuoles, which leads to increased vacuolar solute concentration and therefore higher salt tolerance in transgenic plants. In an effort to engineer cotton for higher drought and salt tolerance, we created transgenic cotton plants expressing AtNHX1. These AtNHX1-expressing cotton plants generated more biomass and produced more fibers when grown in the presence of 200 mM NaCl in greenhouse conditions. The increased fiber yield was probably due to better photosynthetic performance and higher nitrogen assimilation rates observed in the AtNHX1-expressing cotton plants as compared with wild-type cotton plants under saline conditions. Furthermore, the field-grown AtNHX1-expressing cotton plants produced more fibers with better quality, indicating that AtNHX1 can indeed be used for improving salt stress tolerance in cotton.

Salt stress affects the plant growth and productivity worldwide and NHX is one of those genes that are well known to improve salt tolerance in transgenic plants. It is well characterized in several plants, such as Arabidopsis thaliana and cotton; however, not much is known about NHXs in tea plant. In the present study, NHX genes of tea were obtained through a genome-wide search using A. thaliana as reference genome. Out of the 9 NHX genes in tea, 7 genes were localized in vacuole while the remaining 2 genes were localized in the endoplasmic reticulum (ER; CsNHX8) and plasma membrane (PM; CsNHX9), respectively. Furthermore, phylogenetic relationships along with structural analysis which includes gene structure, location, and protein-conserved motifs and domains were systematically examined and further, predictions were validated by the expression analysis. The dN/dS values show that the majority of tea NHX genes is subjected to strong purifying selection under the course of evolution. Also, functional interaction was carried out in Camellia sinensis based on the orthologous genes in A. thaliana. The expression profiles linked to various stress treatments revealed wide involvement of NHX genes from tea in response to various abiotic factors. This study provides the targets for further comprehensive identification, functional study, and also contributed for a better understanding of the NHX regulatory network in C. sinensis. [ABSTRACT FROM AUTHOR]

Salinity and drought are two major environmental stresses that limit the growth and productivity of cotton. To improve cotton's drought and salt tolerance, transgenic cotton plants expressing the Arabidopsis vacuolar Na/H antiporter gene AtNHX1 and H-pyrophosphatase gene AVP1 were produced by cross-pollination of two single-gene-overexpressing plants. The salt tolerance and drought tolerance were further enhanced by simultaneously overexpressing AVP1 and AtNHX1 in comparison to AVP1 or AtNHX1 single-gene-overexpressing plants and to wild-type plants. Plant height, boll number, and fiber yield of AVP1/ AtNHX1-co-overexpressing plants were higher than those of AVP1-overexpressing, AtNHX1-overexpressing, segregated non-transgenic line, and wild-type plants under saline and drought conditions. The photosynthetic rate of AVP1/ AtNHX1-co-overexpressing plants was significantly higher than that of single-gene-overexpressing and wild-type plants under 200 mM NaCl treatment. In addition, the root systems of AVP1/ AtNHX1-co-overexpressing plants were larger than those of single-gene-overexpressing and wild-type plants, which was likely due to increased auxin polar transport in the root systems of the AVP1/ AtNHX1-co-overexpressing plants. Moreover, these AVP1/ AtNHX1-co-overexpressing cotton plants produced 24 % higher fiber yield under low-irrigation conditions and 35 % higher fiber yield under dryland conditions as compared to wild-type cotton in the field. [ABSTRACT FROM AUTHOR]

The Arabidopsis gene AVP1 encodes an H-pyrophosphatase that functions as a proton pump at the vacuolar membranes, generating a proton gradient across vacuolar membranes, which serves as the driving force for many secondary transporters on vacuolar membranes such as Na/H-antiporters. Overexpression of AVP1 could improve drought tolerance and salt tolerance in transgenic plants, suggesting a possible way in improving drought and salt tolerance in crops. The AVP1 was therefore introduced into peanut by Agrobacterium-mediated transformation. Analysis of AVP1-expressing peanut indicated that AVP1-overexpression in peanut could improve both drought and salt tolerance in greenhouse and growth chamber conditions, as AVP1-overexpressing peanuts produced more biomass and maintained higher photosynthetic rates under both drought and salt conditions. In the field, AVP1-overexpressing peanuts also outperformed wild-type plants by having higher photosynthetic rates and producing higher yields under low irrigation conditions. [ABSTRACT FROM AUTHOR]

Salinity is a major environmental stress that affects agricultural productivity worldwide. One approach to improving salt tolerance in crops is through high expression of the Arabidopsis gene AtNHX1, which encodes a vacuolar sodium/proton antiporter that sequesters excess sodium ion into the large intracellular vacuole. Sequestering cytosolic sodium into the vacuoles of plant cells leads to a low level of sodium in cytosol, which minimizes the sodium toxicity and injury to important enzymes in cytosol. In the meantime, the accumulation of sodium in vacuoles restores the correct osmolarity to the intracellular milieu, which favors water uptake by plant root cells and improves water retention in tissues under soils that are high in salt. To improve the yield and quality of peanut under high salt conditions, AtNHX1 was introduced into peanut plants through Agrobacterium-mediated transformation. The AtNHX1-expressing peanut plants displayed increased tolerance of salt at levels up to 150 mM NaCl. When compared to wild-type plants, AtNHX1-expressing peanut plants suffered less damage, produced more biomass, contained more chlorophyll, and maintained higher photosynthetic rates under salt conditions. These data indicate that AtNHX1 can be used to enhance salt tolerance in peanut. [ABSTRACT FROM AUTHOR]