Pyrroline-5-carboxylate Synthase Research Articles

Cellular ATP demand creates metabolically distinct subpopulations of mitochondria.

Mitochondria serve a crucial role in cell growth and proliferation by supporting both ATP synthesis and the production of macromolecular precursors. Whereas oxidative phosphorylation (OXPHOS) depends mainly on the oxidation of intermediates from the tricarboxylic acid cycle, the mitochondrial production of proline and ornithine relies on reductive synthesis1. How these competing metabolic pathways take place in the same organelle is not clear. Here we show that when cellular dependence on OXPHOS increases, pyrroline-5-carboxylate synthase (P5CS)-the rate-limiting enzyme in the reductive synthesis of proline and ornithine-becomes sequestered in a subset of mitochondria that lack cristae and ATP synthase. This sequestration is driven by both the intrinsic ability of P5CS to form filaments and the mitochondrial fusion and fission cycle. Disruption of mitochondrial dynamics, by impeding mitofusin-mediated fusion or dynamin-like-protein-1-mediated fission, impairs the separation of P5CS-containing mitochondria from mitochondria that are enriched in cristae and ATP synthase. Failure to segregate these metabolic pathways through mitochondrial fusion and fission results in cells either sacrificing the capacity for OXPHOS while sustaining the reductive synthesis of proline, or foregoing proline synthesis while preserving adaptive OXPHOS. These findings provide evidence of the key role of mitochondrial fission and fusion in maintaining both oxidative and reductive biosyntheses in response to changing nutrient availability and bioenergetic demand.

Salicylic acid mitigates 'Hayward' kiwifruit chilling injury by regulating hormone and proline metabolism, as well as maintaining cellular structure

The 'Hayward' kiwifruit is extremely susceptible to chilling injury (CI) during the late stages of cold storage, thus limiting its storage quality and life. Therefore, mitigating the losses caused by CI is imperative. Salicylic acid (SA) has been demonstrated to mitigate CI in fruit and vegetables. In this study, we conducted a comparative analysis of proline metabolism, key endogenous hormone levels, as well as the effects on cell structure and membrane lipid oxidation in kiwifruit treated with 1 mM SA during low-temperature storage. The results showed that SA could attenuate lipoxygenase (LOX) activity, enhance catalase (CAT) activity, suppress the elevation of malondialdehyde (MDA) content, mitigate starch granule degradation in cells, and preserve cell structure integrity. Moreover, SA was found to enhance proline biosynthesis by activating ornithine transaminase (OAT) and pyrroline-5-carboxylate synthase (P5CS) while concurrently suppressing proline dehydrogenase (PDH) activity. Additionally, exogenous SA increased endogenous levels of both SA and abscisic acid (ABA), while simultaneously decreasing the concentration of gibberellic acid (GA) in fruit. In conclusion, exogenous SA treatment could alleviate the development of CI in kiwifruit by maintaining cell structure, promoting proline synthesis, and balancing endogenous hormone content. Our study offers a theoretical foundation for understanding the mechanism by which SA mitigates cold damage in kiwifruit, and provides novel insights into the low-temperature preservation of kiwifruit.

Synergistic effect of carbon nanoparticles with mild salinity for improving chemical composition and antioxidant activities of radish sprouts.

The demand for healthy foods with high functional value has progressively increased. Carbon nanoparticles (CNPs) have a promising application in agriculture including the enhancement of plant growth. However, there are few studies on the interactive effects of CNPs and mild salinity on radish seed sprouting. To this end, the effect of radish seed priming with 80mM CNPs on biomass, anthocyanin, proline and polyamine metabolism, and antioxidant defense system under mild salinity growth condition (25 mM NaCl). The results indicated that seed nanopriming with CNPs along with mild salinity stress enhanced radish seed sprouting and its antioxidant capacity. Priming boosted the antioxidant capacity by increasing antioxidant metabolites such as (polyphenols, flavonoids, polyamines, anthocyanin, and proline). To understand the bases of these increases, precursors and key biosynthetic enzymes of anthocyanin [phenylalanine, cinnamic acid, coumaric acid, naringenin, phenylalanine ammonia lyase, chalcone synthase (CHS), cinnamate-4-hydroxylase (C4H) and 4-coumarate: CoA ligase (4CL)], proline [pyrroline-5-carboxylate synthase (P5CS), proline dehydrogenase (PRODH), Sucrose, Sucrose P synthase, invertase) and polyamines [putrescine, spermine, spermidine, total polyamines, arginine decarboxylase, orinthnine decarboxylase, S-adenosyl-L-methionine decarboxylase, spermidine synthase, spermine synthase] were analyzed. In conclusion, seed priming with CNPs has the potential to further stimulate mild salinity-induced bioactive compound accumulation in radish sprouts.

Elevated level of chilling tolerance in cucumber fruit was obtained by β-aminobutyric acid via the regulation of antioxidative response and metabolism of energy, proline and unsaturated fatty acid

• BABA treatment enhances the chilling tolerance in cucumber fruit. • BABA application improved the antioxidant capacity of harvested cucumber fruit. • BABA-treated fruit exhibited higher level of energy status. • BABA promoted proline accumulation and maintained higher level of UFA contents. This experimental study was conducted to investigate the effects of β-aminobutyric acid (BABA) on chilling injury in cold-stored cucumber fruit. Results showed that BABA decreased the development of chilling injury in cucumber fruit. BABA-treated fruit exhibited elevated antioxidant ability, indicated by high activities of superoxide dismutase (SOD) and catalase (CAT) and low levels of hydrogen peroxide and superoxide anion. BABA treatment maintained a high level of energy status by promoting the activities and genes expression of H + -ATPase, Ca 2+ -ATPase, succinate dehydrogenase (SDH) and cytochrome C oxidase (CCO). Increased enzymes activities and genes expression of Δ 1 -pyrroline-5-carboxylate synthase (PCS) and ornithine-δ-aminotransferase (OAT) and depressed enzyme activity and gene expression of proline dehydrogenase (PDH) in BABA-treated cucumber collectively promoted the accumulation of proline. Furthermore, BABA treatment delayed the decreasing trend of unsaturated fatty acid content in cucumber. Thus, BABA is effective in enhancing chilling tolerance in cucumber fruit possibly by improving the antioxidant ability and adjusting the metabolism of energy, proline and unsaturated fatty acids.

Alpha Lipoic Acid as a Protective Mediator for Regulating the Defensive Responses of Wheat Plants against Sodic Alkaline Stress: Physiological, Biochemical and Molecular Aspects.

Recently, exogenous α-Lipoic acid (ALA) has been suggested to improve the tolerance of plants to a wide array of abiotic stresses. However, there is currently no definitive data on the role of ALA in wheat plants exposed to sodic alkaline stress. Therefore, this study was designed to evaluate the effects of foliar application by ALA at 0 (distilled water as control) and 20 µM on wheat seedlings grown under sodic alkaline stress (50 mM 1:1 NaHCO3 & Na2CO3; pH 9.7. Under sodic alkaline stress, exogenous ALA significantly (p ≤ 0.05) improved growth (shoot fresh and dry weight), chlorophyll (Chl) a, b and Chl a + b, while Chl a/b ratio was not affected. Moreover, leaf relative water content (RWC), total soluble sugars, carotenoids, total soluble phenols, ascorbic acid, K and Ca were significantly increased in the ALA-treated plants compared to the ALA-untreated plants. This improvement was concomitant with reducing the rate of lipid peroxidation (malondialdehyde, MDA) and H2O2. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) demonstrated greater activity in the ALA-treated plants compared to the non-treated ones. Conversely, proline, catalase (CAT), guaiacol peroxidase (G-POX), Na and Na/K ratio were significantly decreased in the ALA-treated plants. Under sodic alkaline stress, the relative expression of photosystem II (D2 protein; PsbD) was significantly up-regulated in the ALA treatment (67% increase over the ALA-untreated plants); while Δ pyrroline-5-carboxylate synthase (P5CS), plasma membrane Na+/H+ antiporter protein of salt overly sensitive gene (SOS1) and tonoplast-localized Na+/H+ antiporter protein (NHX1) were down-regulated by 21, 37 and 53%, respectively, lower than the ALA-untreated plants. These results reveal that ALA may be involved in several possible mechanisms of alkalinity tolerance in wheat plants.

Transcriptomic Analysis Provides Insights into Foliar Zinc Application Induced Upregulation in 2-Acetyl-1-pyrroline and Related Transcriptional Regulatory Mechanism in Fragrant Rice.

The involvement of zinc (Zn) in terms of aroma formation has been rarely investigated. This study shows that the regulation of 2-acetyl-1-pyrroline (2AP) biosynthesis was evaluated in two different rice cultivars under foliar Zn application. The results showed that the 2AP and Zn contents in leaves and grains were improved substantially under foliar Zn application. The 2AP content was positively related to the expression P5CS2 gene, contents of proline, 1-pyrroline, and Δ1-pyrroline-5-carboxylate (P5C), and the activity of pyrroline-5-carboxylate synthase (P5CS) under Zn application in fragrant rice. Multiple transcription factors (TFs) were differently expressed, such as bZIPs, NACs, and MYBs, to play a role under Zn treatments in fragrant rice, suggesting the crucial role of 46 differently expressed TFs in 2AP improvements in fragrant rice. Furthermore, this study showed that the optimal foliar Zn application at a concentration of 30 mg L-1 could increase the 2AP content of aromatic rice and keep the yield stable or increase the yield. TFs were involved in regulating to promote the 2AP formation in aromatic rice under the foliar Zn application. However, the relationship between 2AP biosynthesis pathway genes and TFs in fragrant rice remains to be further studied.

Activation of proline biosynthesis is critical to maintain glutamate homeostasis during acute methamphetamine exposure

Methamphetamine (METH) is a highly addictive psychostimulant that causes long-lasting effects in the brain and increases the risk of developing neurodegenerative diseases. The cellular and molecular effects of METH in the brain are functionally linked to alterations in glutamate levels. Despite the well-documented effects of METH on glutamate neurotransmission, the underlying mechanism by which METH alters glutamate levels is not clearly understood. In this study, we report an essential role of proline biosynthesis in maintaining METH-induced glutamate homeostasis. We observed that acute METH exposure resulted in the induction of proline biosynthetic enzymes in both undifferentiated and differentiated neuronal cells. Proline level was also increased in these cells after METH exposure. Surprisingly, METH treatment did not increase glutamate levels nor caused neuronal excitotoxicity. However, METH exposure resulted in a significant upregulation of pyrroline-5-carboxylate synthase (P5CS), the key enzyme that catalyzes synthesis of proline from glutamate. Interestingly, depletion of P5CS by CRISPR/Cas9 resulted in a significant increase in glutamate levels upon METH exposure. METH exposure also increased glutamate levels in P5CS-deficient proline-auxotropic cells. Conversely, restoration of P5CS expression in P5CS-deficient cells abrogated the effect of METH on glutamate levels. Consistent with these findings, P5CS expression was significantly enhanced in the cortical brain region of mice administered with METH and in the slices of cortical brain tissues treated with METH. Collectively, these results uncover a key role of P5CS for the molecular effects of METH and highlight that excess glutamate can be sequestered for proline biosynthesis as a protective mechanism to maintain glutamate homeostasis during drug exposure.

Mycorrhizal fungi enhance flooding tolerance of peach through inducing proline accumulation and improving root architecture

This study aimed to evaluate the effect of an arbuscular mycorrhizal fungus (AMF) Glomus mosseae on plant growth, root architecture, and proline metabolism in roots of peach (Prunes persica L.) under non-flooding and flooding conditions. The 12-day flooding dramatically inhibited root colonisation of G. mosseae, but induced a large number of extraradical mycelia. Although the flooding treatment also relatively inhibited growth and root architecture of peach, the mycorrhizal fungal inoculation dramatically increased shoot and root biomass, plant height, stem diameter, number of 1<sup>st</sup>- and 2<sup>nd</sup>-order lateral roots, root total length (mainly 0–1 cm and > 3 cm long), root surface area, and root volume under flooding. The study also revealed distinctly higher proline accumulation in the roots of mycorrhizal plants than non-mycorrhizal plants under both non-flooding and flooding conditions, accompanied by higher Δ<sup>1</sup>-pyrroline-5-carboxylate synthase (P5CS) activity and lower δ-ornithine transaminase and proline dehydrogenase activities. In addition, the PpP5CS1 gene expression was up-regulated by flooding and mycorrhization. This study concluded that mycorrhizal fungi enhanced flooding tolerance of peach through inducing proline accumulation and improving root architecture.

Pyrroline-5-carboxylate synthase senses cellular stress and modulates metabolism by regulating mitochondrial respiration.

Pyrroline-5-carboxylate synthase (P5CS) catalyzes the synthesis of pyrroline-5-carboxylate (P5C), a key precursor for the synthesis of proline and ornithine. P5CS malfunction leads to multiple human diseases; however, the molecular mechanism underlying these diseases is unknown. We found that P5CS localizes in mitochondria in rod- and ring-like patterns but diffuses inside the mitochondria upon cellular starvation or exposure to oxidizing agents. Some of the human disease-related mutant forms of P5CS also exhibit diffused distribution. Multimerization (but not the catalytic activity) of P5CS regulates its localization. P5CS mutant cells have a reduced proliferation rate and are sensitive to cellular stresses. Flies lacking P5CS have reduced eclosion rates. Lipid droplets accumulate in the eyes of the newly eclosed P5CS mutant flies, which degenerate with aging. The loss of P5CS in cells leads to abnormal purine metabolism and lipid-droplet accumulation. The reduced lipid-droplet consumption is likely due to decreased expression of the fatty acid transporter, CPT1, and few β-oxidation-related genes following P5CS knockdown. Surprisingly, we found that P5CS is required for mitochondrial respiratory complex organization and that the respiration defects in P5CS knockout cells likely contribute to the metabolic defects in purine synthesis and lipid consumption. This study links amino acid synthesis with mitochondrial respiration and other key metabolic processes, whose imbalance might contribute to P5CS-related disease conditions.

Salubrinal in Combination With 4E1RCat Synergistically Impairs Melanoma Development by Disrupting the Protein Synthetic Machinery.

Increased protein synthesis is a key process in melanoma, which is regulated by the ALDH18A1 gene encoding pyrroline-5-carboxylate synthase (P5CS). P5CS is involved in proline biosynthesis and targeting ALDH18A1 has previously been shown to inhibit melanoma development by decreasing intracellular proline levels to increase the phosphorylation of eIF2α mediated by GCN2, which then impairs mRNA translation. Since there are no current inhibitors of P5CS, decreased eIF2α phosphorylation in melanoma was targeted using salubrinal (a specific inhibitor of eIF2α phosphatase enzymes). While salubrinal alone was ineffective, the combined use of salubrinal and 4E1RCat (a dual inhibitor of eIF4E:4E-BP1 and eIF4E:eIF4G interaction to prevent assembly of the eIF4F complex and inhibit cap-dependent translation) was found to be effective at decreasing protein synthesis, protein translation, and cell cycle progression to synergistically decrease melanoma cell viability and inhibited xenograft melanoma tumor development. The combination of these agents synergistically decreased melanoma cell viability while having minimal effect on normal cells. This is the first report demonstrating that it is possible to inhibit melanoma viability by targeting eIF2α signaling using salubrinal and 4E1RCat to disrupt assembly of the eIF4F complex.

Genotype-Dependent Differences between Cereals in Response to Manganese Excess in the Environment

Industrial and agronomic activities lead to oversupply and accumulation of elements in the environment. Relatively little is known about mechanisms of manganese (Mn) triggered stress. In this study, different cultivars of popular cereals wheat, oat, and barley were investigated for their response to excessive Mn. Manganese ions (MnCl2) at 5 and 10 mM were applied to the grains and then to the media on which the plants grew until they developed their first leaf. It was performed ICP MS aiming to understand the mechanism of manganese stress in susceptible and resistant cultivar. Under Mn-stress a decrease in fresh weight of plants was observed, also differences in water content in first leaves, an increase in superoxide dismutases (SOD) and peroxidases (POX) activity, and a significant rise in catalase (CAT) was only characteristic for barley. Increasing Mn concentration resulted in enhancing of manganese superoxide dismutase (Mn-SOD) and copper, zinc superoxide dismutase (Cu/Zn-SOD) bands intensity. The increase in proline content, depending on a balance between pyrroline-5-carboxylate synthase (P5CS), ornithine-d-aminotransferase (OAT), and proline dehydrogenases (PHD) activities, indicated osmotic disorders in all plants and differentiated the studied cereals. Microscopic observations of changes in the structure of plastids and starch accumulation in Mn presence were particularly visible in sensitive cultivars. The study ranked the tested cereals in terms of their tolerance to Mn from the most tolerant wheat through barley and the least tolerant oats.

A R2R3-MYB transcription factor VvMYBF1 from grapevine (Vitis vinifera L.) regulates flavonoids accumulation and abiotic stress tolerance in transgenic Arabidopsis

ABSTRACTTranscriptional regulation is the most important tool for enhancing flavonoid biosynthesis of plants. The grapevine VvMYBF1 gene has been shown to be involved in the regulation of flavonoid biosynthesis. However, very little is known about its roles in tolerance to abiotic stresses. In this study, VvMYBF1 gene was cloned from grapevine. Its overexpression significantly increased accumulation of flavonoids and salt and drought tolerance in transgenic Arabidopsis. Real-time quantitative PCR analysis showed that overexpression of VvMYBF1 up-regulated the genes related to flavonoid and proline biosynthesis, stress responses and ROS scavenging under salt and drought stresses. Further components analyses showed that the transgenic plants exhibited significant increases of total flavonoids and proline content, as well as significant reduction of H2O2 and malonaldehyde (MDA) content. Enzymatic analyses found that the significant increases of phenylalanine ammonia lyase (PAL), chalcone isomerase (CHI), flavonol synthase (FLS), dihydroflavonol reductase (DFR), pyrroline-5-carboxylate synthase (P5CS), superoxide dismutase (SOD) and peroxidase (POD) activities were observed in the transgenic plants. These findings imply functions of VvMYBF1 in accumulation of flavonoids and tolerance to salt and drought stresses. The VvMYBF1 gene has the potential to be used to increase the content of valuable flavonoids and improve tolerance to abiotic stresses in plants.

A R2R3-type MYB transcription factor gene from soybean, GmMYB12, is involved in flavonoids accumulation and abiotic stress tolerance in transgenic Arabidopsis

The R2R3-type MYB transcription factors have been shown to increase flavonoids accumulation by regulating the expression of key enzyme genes related to flavonoid biosynthesis pathway. However, the roles and underlying mechanisms of the soybean GmMYB12 gene in regulation of flavonoids accumulation and tolerance to abiotic stresses are rarely known. In the present study, the GmMYB12 gene was isolated and its function was characterized. Sequence and yeast one-hybrid analyses showed that GmMYB12 contained two MYB domains and belonged to R2R3-MYB protein with transactivation activity. Subcellular localization analysis in onion epidermal cells indicated that GmMYB12 was localized to the nucleus. Overexpression of GmMYB12 increased the production of downstream flavonoids and the expression of related genes in the flavonoid biosynthesis pathway. It also improved resistance to salt and drought stresses during seed germination, root development, and growing stage. Further component and enzymatic analyses showed significant increases of proline content, pyrroline-5-carboxylate synthase (P5CS), superoxide dismutase (SOD), and peroxidase (POD) activities, as well as significant reduction of H2O2 and malonaldehyde (MDA) content under salt and drought stresses in transgenic plants. Meanwhile, the expression level of AtP5CS, AtSOD and AtPOD genes was up-regulated against salt and drought stresses. Together, our finding indicated that changing the expression level of GmMYB12 in plants alters the accumulation of flavonoids and regulates plantlet tolerance to abiotic stress by regulating osmotic balance, protecting membrane integrity and maintaining ROS homeostasis. The GmMYB12 gene has the potential to be used to increase the content of valuable flavonoids and improve the tolerance to abiotic stresses in plants.

Abscisic acid cross-talking with hydrogen peroxide and osmolyte compounds may regulate the leaf rolling mechanism under drought

Leaf rolling observed in some crops such as maize, rice, wheat and sorghum is an indicator of decreased water status. Moderate leaf rolling not tightly or early increases the photosynthesis and grain yield of crop cultivars under environmental stresses. Moreover, the effects of exogenous abscisic acid (ABA) on stomatal conductance, water status and synthesis of osmotic compounds are a well-known issue in plants subjected to water deficit. However, it is not clear how the cross-talk of ABA with H2O2 and osmolyte compounds affects the leaf rolling mechanism. Regulation mechanism of leaf rolling by ABA has been first studied in maize seedlings under drought stress induced by polyethylene glycol 6000 (PEG 6000) in this study. ABA treatment under drought stress reduced hydrogen peroxide (H2O2) content and the degree of leaf rolling (%) while the treatment-induced ABA synthesis, osmolyte levels (proline, polyamine and total soluble sugars) and some antioxidant enzyme activities in comparison to the plants that were not treated with ABA. Furthermore, exogenous ABA up-regulated the expression levels of arginine decarboxylase (ADC) and pyrroline-5-carboxylate synthase (P5CS) genes and down-regulated polyamine oxidase (PAO), diamine oxidase (DAO) and proline dehydrogenase (ProDH) gene expressions. When endogenous ABA content was decreased by the treatment of fluoridone (FLU) that is an ABA inhibitor, leaf rolling degree (%), H2O2 content and antioxidant enzyme activities increased, but osmolyte levels, ADC and P5CS gene expressions decreased. Finally, the treatment of ABA to maize seedlings exposed to drought stress resulted in the stimulation of the antioxidant system, osmotic adjustment and reduction of leaf rolling. We concluded that ABA can be a signal compound cross-talking H2O2, proline and polyamines and thus involved in the leaf rolling mechanism by providing osmotic adjustment. The results of this study can be used to provide data for the molecular breeding of maize hybrids with high grain yield by means of moderately rolled leaves.

Efficacy of FeSO4 nano formulations on osmolytes and antioxidative enzymes of sunflower under salt stress

This study investigated iron (II) sulfate (FeSO4) effects in two forms on some antioxidant enzyme activity, osmoregulators and sunflower growth under salt stress. Treatments included five cultivars (Alstar, Olsion, Yourflor, Hysun36 and Hysun33), two salinity levels (control and 100 mM NaCl), and three foliar applications (none-sprayed, FeSO4 normal and nano-particles at a rate of 2 g L−1). As a results, salt stress increased superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO), peroxidase (POX), pyrroline-5-carboxylate synthase (P5CS) and invertase activities; and also proline, soluble carbohydrates, malondialdehyde (MDA) content and reactive oxygen species (ROS) generation; however, reduced shoot dry weight and seed yield. Foliar spray of FeSO4 in two forms enhanced CAT, PPO, POX, invertase activity, soluble carbohydrates and decreased MDA content and ROS generation compared to non-sprayed plants under saline condition. In general, FeSO4 in nano was more effective than normal form in improving the growth of sunflower. As an average, the spray of FeSO4 increased proline content of Alestar cultivar under 100 mM salinity, which related with P5CS activity but reduced leaf proline content of Olsion and Hysun33 under non-saline condition. In addition, shoot dry weight and seed yield of sunflower were increased by FeSO4. Leaf Fe concentration of cultivars was strongly intensified by FeSO4 foliar spray under two conditions compared to non-sprayed treatment. Overall, the usage of FeSO4 alleviated the negative impact of salt stress, although the positive effects of nano-particles were more than the normal form.

Inoculation with the endophyte Piriformospora indica significantly affects mechanisms involved in osmotic stress in rice

BackgroundRice is a drought susceptible crop. A symbiotic association between rice and mycorrhizal fungi could effectively protect the plant against sudden or frequent episodes of drought. Due to its extensive network of hyphae, the endophyte is able to deeply explore the soil and transfer water and minerals to the plant, some of them playing an important role in mitigating the effects of drought stress. Moreover, the endophyte could modify the expression of drought responsive genes and regulate antioxidants.ResultsThree rice genotypes, WC-297 (drought tolerant), Caawa (moderately drought tolerant) and IR-64 (drought susceptible) were inoculated with Piriformospora indica (P. indica), a dynamic endophyte. After 20 days of co-cultivation with the fungus, rice seedlings were subjected to 15% polyethylene glycol-6000 induced osmotic stress. P. indica improved the growth of rice seedlings. It alleviated the destructive effects of the applied osmotic stress. This symbiotic association increased seedling biomass, the uptake of phosphorus and zinc, which are functional elements for rice growth under drought stress. It boosted the chlorophyll fluorescence, increased the production of proline and improved the total antioxidant capacity in leaves. The association with the endophyte also up regulated the activity of the Pyrroline-5-carboxylate synthase (P5CS), which is critical for the synthesis of proline.ConclusionA mycorrhizal association between P. indica and rice seedlings provided a multifaceted protection to rice plants under osmotic stress (− 0.295 MPa).

RNA-seq analysis reveals alternative splicing under salt stress in cotton, Gossypium davidsonii

BackgroundNumerous studies have focused on the regulation of gene expression in response to salt stress at the transcriptional level; however, little is known about this process at the post-transcriptional level.ResultsUsing a diploid D genome wild salinity-tolerant cotton species, Gossypium davidsonii, we analyzed alternative splicing (AS) of genes related to salt stress by comparing high-throughput transcriptomes from salt-treated and well-watered roots and leaves. A total of 14,172 AS events were identified involving 6798 genes, of which intron retention (35.73%) was the most frequent, being detected in 3492 genes. Under salt stress, 1287 and 1228 differential alternative splicing (DAS) events were identified in roots and leaves, respectively. These DAS genes were associated with specific functional pathways, such as “responses to stress”, “metabolic process” and “RNA splicing”, implying that AS represents an important pathway of gene regulation in response to salt stress. Several salt response genes, such as pyrroline-5-carboxylate synthase (P5CS), K+ channel outward (KCO1), plasma membrane intrinsic protein (PIP) and WRKY33 which were involved in osmotic balance, ion homeostasis, water transportation and transcriptional regulation, respectively, were identified with differential alternative splicing under salt stress. Moreover, we revealed that 13 genes encoding Ser/Arg-rich (SR) proteins related to AS regulation were differentially alternatively spliced under salt stress.ConclusionThis study first provide a comprehensive view of AS in G. davidsonii, and highlight novel insights into the potential roles of AS in plant responses to salt stress.

Heat responsive proteome changes reveal molecular mechanisms underlying heat tolerance in chickpea

Understanding the molecular differences in plant genotypes contrasting for heat sensitivity can provide useful insights into the mechanisms that confer heat tolerance in plants. This study focuses on comparative physiological and proteomic analyses of heat-sensitive (ICC16374) and heat-tolerant (JG14) genotypes of chickpea (Cicer arietinum L.) under heat stress impositions at anthesis. Heat stress reduced leaf water content, chlorophyll content and membrane integrity with a greater impact on the sensitive genotype compared to the tolerant one that had higher total antioxidant capacity and osmolyte accumulation, and consequently less oxidative damage. This study identified a set of 482 heat-responsive proteins in the tolerant genotype using comparative gel-free proteomics. Besides heat shock proteins, proteins such as acetyl-CoA carboxylase, pyrroline-5-carboxylate synthase (P5CS), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), phenylalanine ammonia-lyase (PAL) 2, ATP synthase, glycosyltransferase, sucrose synthase and late embryogenesis abundant (LEA) proteins were strongly associated with heat tolerance in chickpea. Several crucial proteins were induced by heat exclusively in the heat-tolerant genotype. Comparative proteome profiling and pathway analysis revealed mitigating strategies including, accumulation of osmoprotectants, protected membrane transport, ribosome and secondary metabolite synthesis, activation of antioxidant and defense compounds, amino acid biosynthesis, and hormonal modulation that might play key roles in chickpea heat tolerance. This study potentially contributes to improved stress resilience by advancing our understanding on the mechanisms of heat tolerance in chickpea.

PGPR-mediated expression of salt tolerance gene in soybean through volatiles under sodium nitroprusside.

Increasing evidence shows that nitric oxide (NO), a typical signaling molecule plays important role in development of plant and in bacteria-plant interaction. In the present study, we tested the effect of sodium nitroprusside (SNP)-a nitric oxide donor, on bacterial metabolism and its role in establishment of PGPR-plant interaction under salinity condition. In the present study, we adopted methods namely, biofilm formation assay, GC-MS analysis of bacterial volatiles, chemotaxis assay of root exudates (REs), measurement of electrolyte leakage and lipid peroxidation, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for gene expression. GC-MS analysis revealed that three new volatile organic compounds (VOCs) were expressed after treatment with SNP. Two VOCs namely, 4-nitroguaiacol and quinoline were found to promote soybean seed germination under 100 mM NaCl stress. Chemotaxis assay revealed that SNP treatment, altered root exudates profiling (SS-RE), found more attracted to Pseudomonas simiae bacterial cells as compared to non-treated root exudates (S-RE) under salt stress. Expression of Peroxidase (POX), catalase (CAT), vegetative storage protein (VSP), and nitrite reductase (NR) genes were up-regulated in T6 treatment seedlings, whereas, high affinity K+ transporter (HKT1), lipoxygenase (LOX), polyphenol oxidase (PPO), and pyrroline-5-carboxylate synthase (P5CS) genes were down-regulated under salt stress. The findings suggest that NO improves the efficiency and establishment of PGPR strain in the plant environment during salt condition. This strategy may be applied on soybean plants to increase their growth during salinity stress.

A vacuolar Na+/H+ antiporter gene, IbNHX2, enhances salt and drought tolerance in transgenic sweetpotato

Plant vacuolar Na+/H+ antiporters (NHX) play a critical role in adaption to abiotic stresses by compartmentalizing Na+ into vacuoles from the cytosol. In this study, a vacuolar Na+/H+ antiporter gene, named IbNHX2, was isolated and characterized from salt-tolerant sweetpotato (Ipomoea batatas (L.) Lam.) line ND98. IbNHX2 consisted of 542 amino acid residues with a conserved binding domain ‘FFIYLLPPI’ for amiloride and a cation/H+ exchanger domain, and shared a high amino acid identity (73.72–96.13%) with the identified vacuolar Na+/H+ antiporters in other plant species. The genomic DNA of IbNHX2 contained 14 exons and 13 introns. Expression of IbNHX2 was induced by abscisic acid (ABA), NaCl and polyethylene glycol (PEG). Its overexpression significantly enhanced salt and drought tolerance in the transgenic sweetpotato. An significant increase of proline content and superoxide dismutase (SOD) and photosynthesis activities and significant reduction of malonaldehyde (MDA) and H2O2 content were found in the transgenic sweetpotato plants. Up-regulation of the stress-responsive genes encoding pyrroline-5-carboxylate synthase (P5CS), SOD, catalase (CAT), zeaxanthinepoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED), aldehyde oxidase (AO), late embryogenesis abundant protein (LEA), psbA and phosphoribulokinase (PRK) in the transgenic plants was also found under salt and drought stresses. The overall results demonstrate the explicit role of IbNHX2 in conferring salt and drought tolerance of sweetpotato. The IbNHX2 gene has the potential to be used for improving salt and drought tolerance of plants.