Proteomic response of oat leaves to long-term salinity stress

Trends and Directions in Oats Research under Drought and Salt Stresses: A Bibliometric Analysis (1993-2023)

With global climate change leading to increasing intensity and frequency of droughts, as well as the growing problem of soil salinization, these factors significantly affect crop growth, yield, and resilience to adversity. Oats are a cereal widely grown in temperate regions and are rich in nutritive value; however, the scientific literature on the response of oat to drought and salt stress has not yet been analyzed in detail. This study comprehensively analyzed the response of oat to drought stress and salt stress using data from the Web of Science core database and bibliometric methods with R (version4.3.1), VOSviewer (version 1.6.19), and Citespace (version6.3.1.0) software. The number of publications shows an increasing trend in drought stress and salt stress in oat over the past 30 years. In the field of drought-stress research, China, the United States, and Canada lead in terms of literature publication, with the most academic achievements being from China Agricultural University and Canadian Agricultural Food University. The journal with the highest number of published papers is Field Crops Research. Oat research primarily focuses on growth, yield, physiological and biochemical responses, and strategies for improving drought resistance. Screening of drought-tolerant genotypes and transformation of drought-tolerant genes may be key directions for future oat drought research. In the field of salt-stress research, contributions from China, the United States, and India stand out, with the Chinese Academy of Agricultural Sciences and Inner Mongolia Agricultural University producing the most significant research results. The largest number of published articles has been found in the Physiologia Plantarum journal. Current oat salt-stress research primarily covers growth, physiological and biochemical responses, and salt-tolerance mechanisms. It is expected that future oat salt research will focus more on physiological and biochemical responses, as well as gene-editing techniques. Despite achievements under single-stress conditions, combined drought and salt-stress effects on oat remain understudied, necessitating future research on their interaction at various biological levels. The purpose of this study is to provide potential theoretical directions for oat research on drought and salt stress.

Smart reprograming of plants against salinity stress using modern biotechnological tools

Climate change gives rise to numerous environmental stresses, including soil salinity. Salinity/salt stress is the second biggest abiotic factor affecting agricultural productivity worldwide by damaging numerous physiological, biochemical, and molecular processes. In particular, salinity affects plant growth, development, and productivity. Salinity responses include modulation of ion homeostasis, antioxidant defense system induction, and biosynthesis of numerous phytohormones and osmoprotectants to protect plants from osmotic stress by decreasing ion toxicity and augmented reactive oxygen species scavenging. As most crop plants are sensitive to salinity, improving salt tolerance is crucial in sustaining global agricultural productivity. In response to salinity, plants trigger stress-related genes, proteins, and the accumulation of metabolites to cope with the adverse consequence of salinity. Therefore, this review presents an overview of salinity stress in crop plants. We highlight advances in modern biotechnological tools, such as omics (genomics, transcriptomics, proteomics, and metabolomics) approaches and different genome editing tools (ZFN, TALEN, and CRISPR/Cas system) for improving salinity tolerance in plants and accomplish the goal of "zero hunger," a worldwide sustainable development goal proposed by the FAO.

Changes in leaf ecophysiological traits and proteome profile provide new insights into variability of salt response in the succulent halophyte Cakile maritima

Natural variability of stress tolerance in halophytic plants is of significance both ecologically and in view of identifying molecular traits for salt tolerance in plants. Using ecophysiological and proteomic analyses, we address these phenomena in two Tunisian accessions of the oilseed halophyte, Cakile maritima Scop., thriving on arid and semi-arid Mediterranean bioclimatic stages (Djerba and Raoued, respectively), with a special emphasis on the leaves. Changes in biomass, photosynthetic gas exchange and pigment concentrations in C. maritima plants treated with three salinity levels (0, 100 and 300mM NaCl) were monitored for 1month. Comparative two-dimensional gel electrophoresis (2-DE) revealed 94 and 56 proteins of differential abundance in Raoued and Djerba accessions, respectively. These salinity-responsive proteins were mainly related to photosynthesis and oxidative phosphorylation (OXPHOS). Although Djerba accession showed a lower biomass productivity, it showed a slightly higher CO2 assimilation rate than Raoued accession when salt-treated. Photosynthesis impairment in both accessions under salinity was also suggested by the lower abundance of proteins involved in Calvin cycle and electron transfer. A significant increase of protein spots involved in the OXPHOS system was found in Djerba accession, suggesting an increase in mitochondrial respiration for increased ATP production under saline conditions, whereas a lesser pronounced trend was observed for Raoued accession. The latter showed in addition higher abundance of proteins involved in photorespiration. Salt-challenged plants of Djerba also likely developed mechanisms for scavenging ROS in leaves as shown by the increase in superoxide dismutase and thioredoxin, while an opposite trend was found in Raoued.

The Absence of the AtSYT1 Function Elevates the Adverse Effect of Salt Stress on Photosynthesis in Arabidopsis

Arabidopsis thaliana SYNAPTOTAGMIN 1 (AtSYT1) was shown to be involved in responses to different environmental and biotic stresses. We investigated gas exchange and chlorophyll a fluorescence in Arabidopsis wild-type (WT, ecotype Col-0) and atsyt1 mutant plants irrigated for 48 h with 150 mM NaCl. We found that salt stress significantly decreases net photosynthetic assimilation, effective photochemical quantum yield of photosystem II (Φ_PSII), stomatal conductance and transpiration rate in both genotypes. Salt stress has a more severe impact on atsyt1 plants with increasing effect at higher illumination. Dark respiration, photochemical quenching (qP), non-photochemical quenching and Φ_PSII measured at 750 µmol m⁻² s⁻¹ photosynthetic photon flux density were significantly affected by salt in both genotypes. However, differences between mutant and WT plants were recorded only for qP and Φ_PSII. Decreased photosynthetic efficiency in atsyt1 under salt stress was accompanied by reduced chlorophyll and carotenoid and increased flavonol content in atsyt1 leaves. No differences in the abundance of key proteins participating in photosynthesis (except PsaC and PsbQ) and chlorophyll biosynthesis were found regardless of genotype or salt treatment. Microscopic analysis showed that irrigating plants with salt caused a partial closure of the stomata, and this effect was more pronounced in the mutant than in WT plants. The localization pattern of AtSYT1 was also altered by salt stress.

Choline Chloride Mediates Salinity Tolerance in Cluster Bean (Cyamopsis tetragonoloba L.) by Improving Growth, Oxidative Defense, and Secondary Metabolism

Choline chloride (CC) application enhanced the tolerance of cluster bean (Cyamopsis tetragonoloba L.) against salinity stress. The aim of the study was to determine the protective role of CC on plant growth, photosynthesis, and biochemical indicators of oxidative stress. The seeds of BR-99 (tolerant) and BR-2017 (sensitive) were surface sterilized and sown in plastic pots containing river sandy soil. The design of the experiments was completely randomized with 4 replicates per treatment. Three weeks after germination, salinity (150 mM) was imposed. Then plants were sprayed with different concentrations of CC (3, 5, and 10 mM), while normal plants were sprayed with distilled water. Salinity decreased growth attributes, relative water contents, photosynthetic attributes, total soluble proteins, total free amino acids, phenolic, flavonoids, ascorbic acid, proline, and glycine betaine and increased the levels of oxidative stress indicators. However, the application of CC (particularly 5 mM) improved growth attributes, photosynthetic pigments, and activities of antioxidant compounds by reducing the levels of H2O2, malondialdehyde in salt-stressed plants in both cluster bean varieties. BR-99 variety showed more tolerance to salinity stress than that of BR-2017 in the form of greater oxidative defense and osmotic adjustment and clear from greater plant dry masses. Thus, our results showed that the application of CC (5 mM) is an efficient strategy for field use in the areas, where salt stress soils limit agriculture production.

Proteomic Responses to Alkali Stress in Oats and the Alleviatory Effects of Exogenous Spermine Application

Alkali stress limits plant growth and yield more strongly than salt stress and can lead to the appearance of yellow leaves; however, the reasons remain unclear. In this study, we found that (1) the down-regulation of coproporphyrinogen III oxidase, protoporphyrinogen oxidase, and Pheophorbide a oxygenase in oats under alkali stress contributes to the appearance of yellow leaves (as assessed by proteome and western blot analyses). (2) Some oat proteins that are involved in the antioxidant system, root growth, and jasmonic acid (JA) and indole-3-acetic acid (IAA) synthesis are up-regulated in response to alkalinity and help increase alkali tolerance. (3) We added exogenous spermine to oat plants to improve their alkali tolerance, which resulted in higher chlorophyll contents and plant dry weights than in plants subjected to alkaline stress alone. This was due to up-regulation of chitinase and proteins related to chloroplast structure, root growth, and the antioxidant system. Spermine addition increased sucrose utilization efficiency, and promoted carbohydrate export from leaves to roots to increase energy storage in roots. Spermine addition also increased the IAA and JA contents required for root growth.

Response of oat morphologies, root exudates, and rhizosphere fungal communities to amendments in a saline-alkaline environment

The application of organic amendments to saline-alkaline soil has been recommended as an agricultural strategy to improve crop productivity and soil health. However, there has been limited research on how organic soil amendment strategies affect the health of oats and their associated rhizosphere fungal communities in saline-alkaline conditions. Thus, the objectives of this study were to understand the effects of oat cultivars with contrasting saline-alkaline tolerances and different amendments on plant morphologies, root exudates (soluble sugars and organic acids), and rhizosphere fungal communities in a saline-alkaline environment. Experiments were conducted on a saline-alkaline tolerant cultivar, Baiyan2, and a saline-alkaline sensitive cultivar, Caoyou1, under four different organic amendment strategies: 1. control (no amendment application), 2. bio-fertilizer application, 3. rotten straw application, and 4. a co-application of bio-fertilizer and rotten straw. Results showed that plant morphological characters of Baiyan2 were better than Caoyou1, and that soluble sugar and organic acid levels in the rhizosphere of Baiyan2 were significantly lower than Caoyou1. Compared to the control, oat root and plant development was significantly improved by the combined bio-fertilizer and rotten straw amendment. Bio-fertilizer application promoted malic and citric acid levels, contributing to a higher total organic acid level, and significantly increased the abundance of Rhizopus arrhizus and decreased the abundance of the fungal pathogens Alternaria, Cladosporium, Sarocladium and Heydenia of Ascomycota in both oat cultivars. All amendment treatments containing rotten straw, except the combined amendment in Baiyan2, significantly increased the relative abundance of Ascomycota (specifically Gibberella, Talaromyces, Fusarium, and Bipolaris) and decreased the relative abundance of R. arrhizus by reducing soluble sugar and organic acid levels. For the combined amendment in Baiyan2, there were no significant changes in Gibberella and Rhizopus between the control and amendment treatment. Our results suggest that co-application of bio-fertilizer and rotten straw, combined with a tolerant oat cultivar, is an effective method to increase crop productivity and enhance soil health in a saline-alkaline environment.

Bio-fertilizer and rotten straw amendments alter the rhizosphere bacterial community and increase oat productivity in a saline-alkaline environment

Saline–alkaline conditions can limit crop productivity and the role of soil microbes in nutrient cycling in arid and semi-arid regions throughout the world. A better understanding of how soil amendments and plant varieties affect rhizosphere microbial communities in saline–alkaline environments is important for the development of sustainable and productive agricultural systems under these challenging conditions. The objective of this study was to determine the effect of organic soil amendments on crop yield, soil physicochemical properties and rhizosphere bacterial communities of two oat cultivars in a saline–alkaline soil. The experiment was conducted in a semi-arid region of Northern China and involved growing two oat cultivars with varying levels of saline–alkaline tolerance under four different amendment treatments: (1) control (no amendments), (2) bio-fertilizer, (3) rotten straw, and (4) combination of bio-fertilizer and rotten straw. The combined bio-fertilizer and rotten straw amendment treatment resulted in the highest oat yields, reduced soil pH, and increased soil salt content for both cultivars. Baiyan2 (tolerant cultivar) had a higher bacterial α-diversity, relative abundance of Proteobacteria and Acidobacteria, and lower relative abundance of Firmicutes compared to Caoyou1 (sensitive cultivar). The rotten straw treatment and combined amendment treatment decreased bacterial α-diversity and the abundance of Proteobacteria, and increased the abundance of Firmicutes, which were positively correlated with soil salt, available nitrogen, phosphorous and potassium for both cultivars. Our study suggested using tolerant oat cultivars with the combined application of rotten straw and bio-fertilizer could be an effective strategy in remediating saline–alkaline soils.

Interactive proteogenomic exploration of response to Fusarium head blight in oat varieties with different resistance

Fusarium species are cereal pathogens that cause the Fusarium Head Blight (FHB) disease. FHB can reduce yield, cause mycotoxin accumulation in the grain and reduce germination efficiency of the harvested seeds. Understanding the biochemical interactions between the host plants and the pathogen is crucial for controlling the disease and for the development of cultivars with improved tolerance to FHB. Here, we studied morphological and proteomic differences between the susceptible oat variety Belinda and the more resistant variety Argamak using variety-specific transcriptome assemblies as references. Measurements of deoxynivalenol toxin levels confirmed the partial resistance in Argamak and the susceptibility in Belinda. To jointly investigate the proteomics- and sequence data, we developed an RShiny-based interface for interactive exploration of the dataset using univariate and multivariate statistics. When applying this interface to the dataset, quantitative protein differences between Belinda and Argamak were detected, and eighteen peptides were found uniquely in Argamak during infection, among them several lipoxygenases. Such proteins can be developed as markers for Fusarium resistance breeding. In conclusion, this study provides the first proteogenomic insight on molecular Fusarium-oat interactions at both morphological and molecular levels and the data are openly available through an interactive interface for further inspection. SIGNIFICANCE: Fusarium head blight causes widespread damage to crops, and chronic and acute toxicity to human and livestock due to the accumulation of toxins during infection. In the present study, two oat varieties with differing resistance were challenged with Fusarium to understand the disease better, and studied both at morphological and molecular levels, identifying proteins which could play a role in the defense mechanism. Furthermore, a proteogenomics approach allows joint profiling of expression and sequence level differences to identify potentially functionally differing mutations. Here such analysis is made openly available through an interactive interface which allows other scientists to draw further findings from the data. This study may both serve as a basis for understanding oat disease response and developing breeding markers for Fusarium resistant oat and future proteogenomic studies using the interactive approach described.

The role and proteomic analysis of ethylene in hydrogen gas-induced adventitious rooting development in cucumber (Cucumis sativus L.) explants

Previous studies have shown that both hydrogen gas (H₂) and ethylene (ETH) play positive roles in plant adventitious rooting. However, the relationship between H₂and ETH during this process has not been explored and remains insufficiently understood. In this study, cucumber (Cucumis sativus L.) was used to explore the proteomic changes in ETH-H₂-induced rooting. Our results show that hydrogen-rich water (HRW) and ethylene-releasing compound (ethephon) at proper concentrations promote adventitious rooting, with maximal biological responses occurring at 50% HRW or 0.5 µM ethephon. ETH inhibitors aminoethoxyvinylglycine (AVG) and AgNO₃ cause partial inhibition of adventitious rooting induced by H₂, suggesting that ETH might be involved in H₂-induced adventitious rooting. According to two-dimensional electrophoresis (2-DE) and mass spectrometric analyses, compared with the control, 9 proteins were up-regulated while 15 proteins were down-regulated in HRW treatment; four proteins were up-regulated while 10 proteins were down-regulated in ethephon treatment; and one protein was up-regulated while nine proteins were down-regulated in HRW+AVG treatment. Six of these differentially accumulated proteins were further analyzed, including photosynthesis -related proteins (ribulose-1,5-bisphosphate carall boxylase smsubunit (Rubisco), sedoheptulose-1,7-bisphosphatase (SBPase), oxygen-evolving enhancer protein (OEE1)), amino and metabolism-related protein (threonine dehydratase (TDH)), stress response-related protein (cytosolic ascorbate peroxidase (CAPX)), and folding, modification and degradation-related protein (protein disulfide-isomerase (PDI)). Moreover, the results of real-time PCR about the mRNA levels of these genes in various treatments were consistent with the 2-DE results. Therefore, ETH may be the downstream signaling molecule during H₂- induced adventitious rooting and proteins Rubisco, SBPase, OEE1, TDH, CAPX and PDI may play important roles during the process.

CRISPR/Cas9-Induced Mutagenesis of Semi-Rolled Leaf1,2 Confers Curled Leaf Phenotype and Drought Tolerance by Influencing Protein Expression Patterns and ROS Scavenging in Rice (Oryza sativa L.)

Rice leaf morphology is an essential agronomic trait to develop drought-tolerant genotypes for adequate and stable crop production in drought-prone areas. Here, rolled leaf mutant plants were acquired by CRISPR/Cas9-based mutagenesis of Semi-rolled leaf1,2 (SRL1 and SRL2) genes, and isobaric tags for relative and absolute quantification (iTRAQ) based proteomic analysis was performed to analyze the subsequent proteomic regulation events. Homozygous mutants exhibit decreased chlorophyll content, transpiration rate, stomatal conductance, vascular bundles (VB), stomatal number, and agronomic traits with increased panicle number and bulliform cells (BCs). Under drought stress, mutant plants displayed lower malondialdehyde (MDA) content while higher survival rate, abscisic acid (ABA) content, superoxide dismutase (SOD), catalase (CAT) activities, and grain filling percentage compare with their wild type (WT). Proteomic results revealed that 270 proteins were significantly downregulated, and 107 proteins were upregulated in the mutant line compared with WT. Proteins related to lateral organ boundaries’ (LOB) domain (LBD) were downregulated, whereas abiotic stress-responsive proteins were upregulated in the CRISPR mutant. LBD proteins (Q5KQR7, Q6K713, Q7XGL4, Q8LQH4), probable indole-3-acetic acid-amido synthetase (Q60EJ6), putative auxin transporter-like protein 4 (Q53JG7), Monoculm 1 (Q84MM9) and AP2 (Apetala2) domain-containing protein (Q10A97) were found to be hub-proteins. The hybrids developed from mutant restorers showed a semi-rolled leaf phenotype with increased panicle number, grain number per panicle, and yield per plant. Our findings reveal the intrinsic value of genome editing and expand the knowledge about the network of proteins for leaf rolling and drought avoidance in rice.

Comparative proteomic analysis of okra (Abelmoschus esculentus L.) seedlings under salt stress

Background

Salinization seriously threatens land use efficiency and crop yields across the world. Understanding the mechanisms plants use to protect against salt stress will help breeders develop salt-tolerant vegetable crops. Okra (Abelmoschus esculentus L.) is an important vegetable crop of the mallow family, which is now cultivated in warm regions worldwide. To understand the effects of salt stress on the protein level of okra, a comparative proteomic analysis of okra seedlings grown in the presence of 0 or 300 mmol L^− 1 NaCl treatment was performed using an integrated approach of Tandem Mass Tag labeling and LC-MS/MS integrated approach.

Results

A total of 7179 proteins were identified in this study, for which quantitative information was available for 5774 proteins. In the NaCl/control comparison group, there were 317 differentially expressed proteins (DEPs), of which 165 proteins were upregulated and 152 proteins downregulated in the presence of NaCl. Based on the above data, we carried out a systematic bioinformatics analysis of proteins with information, including protein annotation, domain characteristics, functional classification, and pathway enrichment. Enriched gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the DEPs were most strongly associated with “response to stress” and “protein processing in endoplasmic reticulum”. Furthermore, several heat shock proteins were identified as DEPs.

Conclusions

This information provides a reference direction for further research on the okra proteome in the downstream of the salt stress response, with our data revealing that the responses of okra to salt stress involves by various pathways.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5737-7) contains supplementary material, which is available to authorized users.

iTRAQ-Based Protein Profiling and Biochemical Analysis of Two Contrasting Rice Genotypes Revealed Their Differential Responses to Salt Stress

Salt stress is one of the key abiotic stresses causing huge productivity losses in rice. In addition, the differential sensitivity to salinity of different rice genotypes during different growth stages is a major issue in mitigating salt stress in rice. Further, information on quantitative proteomics in rice addressing such an issue is scarce. In the present study, an isobaric tags for relative and absolute quantitation (iTRAQ)-based comparative protein quantification was carried out to investigate the salinity-responsive proteins and related biochemical features of two contrasting rice genotypes—Nipponbare (NPBA, japonica) and Liangyoupeijiu (LYP9, indica), at the maximum tillering stage. The rice genotypes were exposed to four levels of salinity: 0 (control; CK), 1.5 (low salt stress; LS), 4.5 (moderate salt stress; MS), and 7.5 g of NaCl/kg dry soil (high salt stress, HS). The iTRAQ protein profiling under different salinity conditions identified a total of 5340 proteins with 1% FDR in both rice genotypes. In LYP9, comparisons of LS, MS, and HS compared with CK revealed the up-regulation of 28, 368, and 491 proteins, respectively. On the other hand, in NPBA, 239 and 337 proteins were differentially upregulated in LS and MS compared with CK, respectively. Functional characterization by KEGG and COG, along with the GO enrichment results, suggests that the differentially expressed proteins are mainly involved in regulation of salt stress responses, oxidation-reduction responses, photosynthesis, and carbohydrate metabolism. Biochemical analysis of the rice genotypes revealed that the Na⁺ and Cl⁻ uptake from soil to the leaves via the roots was increased with increasing salt stress levels in both rice genotypes. Further, increasing the salinity levels resulted in increased cell membrane injury in both rice cultivars, however more severely in NPBA. Moreover, the rice root activity was found to be higher in LYP9 roots compared with NPBA under salt stress conditions, suggesting the positive role of rice root activity in mitigating salinity. Overall, the results from the study add further insights into the differential proteome dynamics in two contrasting rice genotypes with respect to salt tolerance, and imply the candidature of LYP9 to be a greater salt tolerant genotype over NPBA.

How Kentucky bluegrass tolerate stress caused by sodium chloride used for road de-icing?

Salts used in road de-icing during winter season inhibit the growth and development of lawn grass species. The mechanism of plant tolerance/sensitivity to such treatments is still not clear. Moreover, there is a lack of fast and non-invasive tool to detect the effect of these salts on plants growth. This study was designed to understand the tolerance mechanism of Kentucky bluegrass plants on salinity, based on some biometric and physiological parameters. In this experiment, we simulated the urban conditions where salts are used intensively for roads de-icing. Germination capacity was evaluated at five salt solutions of NaCl (0, 50, 100, 150 and 200 mM), and physiological parameters were measured during the tillering phase at salinity levels of 0, 150 and 300 mM of NaCl. Seeds of Kentucky bluegrass did not germinate under salinity. During tillering phase, salinity affected length, area and dry mass of roots as well as the relative water content of plants, negatively. Moreover, it influenced the maximum chlorophyll fluorescence yield, quantum yield of photosystem II and electron transport rate at early period of stress. This allows us to recommend these parameters for early detection of soil salinity effects on Kentucky bluegrass plants. It seems to be that the tolerance of this plant towards salinity is based on retaining water content in leaves that allow more efficient functioning of photosynthetic apparatus.

Physiological and TMT-based proteomic analysis of oat early seedlings in response to alkali stress

Oats are an important cereal crop worldwide, and they also serve as a phytoremediation crop to ameliorate salinized and alkalized soils. However, the mechanism of the oat response to alkali remains unclear. Physiological and tandem mass tag (TMT)-based proteomic analyses were employed to elucidate the mechanism of the oat response to alkali stress. Physiological and phenotypic data showed that oat root growth was inhibited more severely than shoot growth after alkali stress. In total, 164 proteins were up-regulated and 241 proteins were down-regulated in roots, and 93 proteins were up-regulated and 139 proteins were down-regulated in shoots. Under high pH stress, transmembrane proton transporters were down-regulated; conversely, organic acid synthesis related enzymes were increased. Transporters of N, P, Fe, Cu and Ca in addition to N assimilation enzymes in the root were highly increased. This result revealed that higher efficiency of P, Fe, Cu and Ca transport, especially higher efficiency of N intake and assimilation, greatly promoted oat root resistance to alkali stress. Furthermore, many resistance proteins, such as late embryogenesis abundant (LEA) mainly in shoots, GDSL esterase lipase mainly in roots, and WD40-like beta propeller repeat families, greatly accumulated to contribute to oat resistance to alkali stress. SIGNIFICANCE: In this study, physiological and tandem mass tag (TMT)-based proteomic analyses were employed to elucidate oats early seedlings in response to alkali stress. Many difference expression proteins were found involving in oats response to alkali stress. Also, higher efficiency transport of P, Fe, Cu, Ca and N greatly promoted oat resistance to alkali stress.