Transcriptomic and Physiological Evidence for the Relationship between Unsaturated Fatty Acid and Salt Stress in Peanut

Comparative Transcriptome Analysis Revealed Candidate Gene Modules Involved in Salt Stress Response in Sweet Basil and Overexpression of ObWRKY16 and ObPAL2 Enhanced Salt Tolerance of Transgenic Arabidopsis

Sweet basil (Ocimum basilicum L.) is an important aromatic plant with high edibility and economic value, widely distributed in many regions of the tropics including the south of China. In recent years, environmental problems, especially soil salinization, have seriously restricted the planting and spread of sweet basil. However, the molecular mechanism of the salt stress response in sweet basil is still largely unknown. In this study, seed germination, seedling growth, and chlorophyll synthesis in sweet basil were inhibited under salt stress conditions. Through comparative transcriptome analysis, the gene modules involved in the metabolic processes, oxidative response, phytohormone signaling, cytoskeleton, and photosynthesis were screened out. In addition, the landscape of transcription factors during salt treatment in sweet basil was displayed as well. Moreover, the overexpression of the WRKY transcription factor-encoding gene, ObWRKY16, and the phenylalanine ammonia-lyase-encoding gene, ObPAL2, enhanced the seed germination, seedling growth, and survival rate, respectively, of transgenic Arabidopsis, suggesting that they might be important candidates for the creation of salt-tolerant sweet basil cultivars. Our data enrich the study on salt responses in sweet basil and provide essential gene resources for genetic improvements in sweet basil in the future.

ASRpro: A machine-learning computational model for identifying proteins associated with multiple abiotic stress in plants

One of the thrust areas of research in plant breeding is to develop crop cultivars with enhanced tolerance to abiotic stresses. Thus, identifying abiotic stress-responsive genes (SRGs) and proteins is important for plant breeding research. However, identifying such genes via established genetic approaches is laborious and resource intensive. Although transcriptome profiling has remained a reliable method of SRG identification, it is species specific. Additionally, identifying multistress responsive genes using gene expression studies is cumbersome. Thus, endorsing the need to develop a computational method for identifying the genes associated with different abiotic stresses. In this work, we aimed to develop a computational model for identifying genes responsive to six abiotic stresses: cold, drought, heat, light, oxidative, and salt. The predictions were performed using support vector machine (SVM), random forest, adaptive boosting (ADB), and extreme gradient boosting (XGB), where the autocross covariance (ACC) and K-mer compositional features were used as input. With ACC, K-mer, and ACC + K-mer compositional features, the overall accuracy of ∼60-77, ∼75-86, and ∼61-78% were respectively obtained using the SVM algorithm with fivefold cross-validation. The SVM also achieved higher accuracy than the other three algorithms. The proposed model was also assessed with an independent dataset and obtained an accuracy consistent with cross-validation. The proposed model is the first of its kind and is expected to serve the requirement of experimental biologists; however, the prediction accuracy was modest. Given its importance for the research community, the online prediction application, ASRpro, is made freely available (https://iasri-sg.icar.gov.in/asrpro/) for predicting abiotic SRGs and proteins.

Synergistic effects of salt and ultraviolet radiation on the rice-field cyanobacterium Nostochopsis lobatus HKAR-21

Environmental variation has a significant impact on how organisms, including cyanobacteria, respond physiologically and biochemically. Salinity and ultraviolet radiation (UVR)-induced variations in the photopigments of the rice-field cyanobacterium Nostochopsis lobatus HKAR-21 and its photosynthetic performance was studied. We observed that excessive energy dissipation after UVR is mostly caused by Non-Photochemical Quenching (NPQ), whereas photochemical quenching is important for preventing photoinhibition. These findings suggest that ROS production may play an important role in the UVR-induced injury. To reduce ROS-induced oxidative stress, Nostochopsis lobatus HKAR-21 induces the effective antioxidant systems, which includes different antioxidant compounds like carotenoids and enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). The study indicates that Nostochopsis lobatus HKAR-21 exposed to photosynthetically active radiation + UV-A + UV-B (PAB) and PAB + NaCl (PABN) had significantly reduced photosynthetic efficiency. Furthermore, maximum ROS was detected in PAB exposed cyanobacterial cells. The induction of lipid peroxidation (LPO) has been investigated to evaluate the impact of UVR on the cyanobacterial membrane in addition to enzymatic defensive systems. The maximal LPO level was found in PABN treated cells. Based on the findings of this research, it was concluded that salinity and UVR had collegial effects on the major macromolecular components of the rice-field cyanobacterium Nostochopsis lobatus HKAR-21.

Research progress on the physiological response and molecular mechanism of cold response in plants

Low temperature is a critical environmental stress factor that restricts crop growth and geographical distribution, significantly impacting crop quality and yield. When plants are exposed to low temperatures, a series of changes occur in their external morphology and internal physiological and biochemical metabolism. This article comprehensively reviews the alterations and regulatory mechanisms of physiological and biochemical indices, such as membrane system stability, redox system, fatty acid content, photosynthesis, and osmoregulatory substances, in response to low-temperature stress in plants. Furthermore, we summarize recent research on signal transduction and regulatory pathways, phytohormones, epigenetic modifications, and other molecular mechanisms mediating the response to low temperatures in higher plants. In addition, we outline cultivation practices to improve plant cold resistance and highlight the cold-related genes used in molecular breeding. Last, we discuss future research directions, potential application prospects of plant cold resistance breeding, and recent significant breakthroughs in the research and application of cold resistance mechanisms.

Genome-Wide Identification and Expression Analysis of the Stearoyl-Acyl Carrier Protein Δ9 Desaturase Gene Family under Abiotic Stress in Barley

Stearoyl-acyl carrier protein (ACP) Δ9 desaturase (SAD) is a critical fatty acid dehydrogenase in plants, playing a prominent role in regulating the synthesis of unsaturated fatty acids (UFAs) and having a significant impact on plant growth and development. In this study, we conducted a comprehensive genomic analysis of the SAD family in barley (Hordeum vulgare L.), identifying 14 HvSADs with the FA_desaturase_2 domain, which were divided into four subgroups based on sequence composition and phylogenetic analysis, with members of the same subgroup possessing similar genes and motif structures. Gene replication analysis suggested that tandem and segmental duplication may be the major reasons for the expansion of the SAD family in barley. The promoters of HvSADs contained various cis-regulatory elements (CREs) related to light, abscisic acid (ABA), and methyl jasmonate (MeJA). In addition, expression analysis indicated that HvSADs exhibit multiple tissue expression patterns in barley as well as different response characteristics under three abiotic stresses: salt, drought, and cold. Briefly, this evolutionary and expression analysis of HvSADs provides insight into the biological functions of barley, supporting a comprehensive analysis of the regulatory mechanisms of oil biosynthesis and metabolism in plants under abiotic stress.

The genus Arachis: an excellent resource for studies on differential gene expression for stress tolerance

Peanut Arachis hypogaea is a segmental allotetraploid in the section Arachis of the genus Arachis along with the Section Rhizomataceae. Section Arachis has several diploid species along with Arachis hypogaea and A. monticola. The section Rhizomataceae comprises polyploid species. Several species in the genus are highly tolerant to biotic and abiotic stresses and provide excellent sets of genotypes for studies on differential gene expression. Though there were several studies in this direction, more studies are needed to identify more and more gene combinations. Next generation RNA-seq based differential gene expression study is a powerful tool to identify the genes and regulatory pathways involved in stress tolerance. Transcriptomic and proteomic study of peanut plants under biotic stresses reveals a number of differentially expressed genes such as R genes (NBS-LRR, LRR-RLK, protein kinases, MAP kinases), pathogenesis related proteins (PR1, PR2, PR5, PR10) and defense related genes (defensin, F-box, glutathione S-transferase) that are the most consistently expressed genes throughout the studies reported so far. In most of the studies on biotic stress induction, the differentially expressed genes involved in the process with enriched pathways showed plant-pathogen interactions, phenylpropanoid biosynthesis, defense and signal transduction. Differential gene expression studies in response to abiotic stresses, reported the most commonly expressed genes are transcription factors (MYB, WRKY, NAC, bZIP, bHLH, AP2/ERF), LEA proteins, chitinase, aquaporins, F-box, cytochrome p450 and ROS scavenging enzymes. These differentially expressed genes are in enriched pathways of transcription regulation, starch and sucrose metabolism, signal transduction and biosynthesis of unsaturated fatty acids. These identified differentially expressed genes provide a better understanding of the resistance/tolerance mechanism, and the genes for manipulating biotic and abiotic stress tolerance in peanut and other crop plants. There are a number of differentially expressed genes during biotic and abiotic stresses were successfully characterized in peanut or model plants (tobacco or Arabidopsis) by genetic manipulation to develop stress tolerance plants, which have been detailed out in this review and more concerted studies are needed to identify more and more gene/gene combinations.

scRNA-seq Reveals the Mechanism of Fatty Acid Desaturase 2 Mutation to Repress Leaf Growth in Peanut (Arachis hypogaea L.)

Fatty Acid Desaturase 2 (FAD2) controls the conversion of oleic acids into linoleic acids. Mutations in FAD2 not only increase the high-oleic content, but also repress the leaf growth. However, the mechanism by which FAD2 regulates the growth pathway has not been elucidated in peanut leaves with single-cell resolution. In this study, we isolated fad2 mutant leaf protoplast cells to perform single-cell RNA sequencing. Approximately 24,988 individual cells with 10,249 expressed genes were classified into five major cell types. A comparative analysis of 3495 differentially expressed genes (DEGs) in distinct cell types demonstrated that fad2 inhibited the expression of the cytokinin synthesis gene LOG in vascular cells, thereby repressing leaf growth. Further, pseudo-time trajectory analysis indicated that fad2 repressed leaf cell differentiation, and cell-cycle evidence displayed that fad2 perturbed the normal cell cycle to induce the majority of cells to drop into the S phase. Additionally, important transcription factors were filtered from the DEG profiles that connected the network involved in high-oleic acid accumulation (WRKY6), activated the hormone pathway (WRKY23, ERF109), and potentially regulated leaf growth (ERF6, MYB102, WRKY30). Collectively, our study describes different gene atlases in high-oleic and normal peanut seedling leaves, providing novel biological insights to elucidate the molecular mechanism of the high-oleic peanut-associated agronomic trait at the single-cell level.

Trichoderma harzianum inoculation promotes sweet sorghum growth in the saline soil by modulating rhizosphere available nutrients and bacterial community

As one of the major abiotic stresses, salinity can affect crop growth and plant productivity worldwide. The inoculation of rhizosphere or endophytic microorganisms can enhance plant tolerance to salt stresses, but the potential mechanism is not clear. In this study, Trichoderma harzianum ST02 was applied on sweet sorghum [Sorghum bicolor (L.) Moench] in a field trial to investigate the effects on microbiome community and physiochemical properties in the rhizosphere soil. Compared with the non-inoculated control, Trichoderma inoculation significantly increased the stem yield, plant height, stem diameter, and total sugar content in stem by 35.52%, 32.68%, 32.09%, and 36.82%, respectively. In addition, Trichoderma inoculation improved the nutrient availability (e.g., N, P, and K) and organic matter in the rhizosphere soil and changed the bacterial community structure and function in both bulk and rhizosphere soil by particularly increasing the relative abundance of Actinobacter and N-cycling genes (nifH, archaeal and bacterial amoA). We proposed that T. harzianum ST02 could promote sweet sorghum growth under saline conditions by regulating available nutrients and the bacterial community in the rhizosphere soil.

Overexpression of the Purple Perilla (Perilla frutescens (L.)) FAD3a Gene Enhances Salt Tolerance in Soybean

The increasingly serious trend of soil salinization inhibits the normal growth and development of soybeans, leading to reduced yields and a serious threat to global crop production. Microsomal ω-3 fatty acid desaturase encoded by the FAD3 gene is a plant enzyme that plays a significant role in α-linolenic acid synthesis via regulating the membrane fluidity to better accommodate various abiotic stresses. In this study, PfFAD3a was isolated from perilla and overexpressed in soybeans driven by CaMV P35S, and the salt tolerance of transgenic plants was then evaluated. The results showed that overexpression of PfFAD3a increased the expression of PfFAD3a in both the leaves and seeds of transgenic soybean plants, and α-linolenic acid content also significantly increased; hence, it was shown to significantly enhance the salt tolerance of transgenic plants. Physiological and biochemical analysis showed that overexpression of PfFAD3a increased the relative chlorophyll content and PSII maximum photochemical efficiency of transgenic soybean plants under salt stress; meanwhile, a decreased accumulation of MDA, H₂O₂, and O2•-, increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbic acid peroxidase (APX), as well as the production of proline and soluble sugar. In summary, the overexpression of PfFAD3a may enhance the salt tolerance in transgenic soybean plants through enhanced membrane fluidity and through the antioxidant capacity induced by C18:3.

Genome-Wide Analysis of the SNARE Family in Cultivated Peanut (Arachis hypogaea L.) Reveals That Some Members Are Involved in Stress Responses

The superfamily of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins mediates membrane fusion during vesicular transport between endosomes and the plasma membrane in eukaryotic cells, playing a vital role in plant development and responses to biotic and abiotic stresses. Peanut (Arachis hypogaea L.) is a major oilseed crop worldwide that produces pods below ground, which is rare in flowering plants. To date, however, there has been no systematic study of SNARE family proteins in peanut. In this study, we identified 129 putative SNARE genes from cultivated peanut (A. hypogaea) and 127 from wild peanut (63 from Arachis duranensis, 64 from Arachis ipaensis). We sorted the encoded proteins into five subgroups (Qa-, Qb-, Qc-, Qb+c- and R-SNARE) based on their phylogenetic relationships with Arabidopsis SNAREs. The genes were unevenly distributed on all 20 chromosomes, exhibiting a high rate of homolog retention from their two ancestors. We identified cis-acting elements associated with development, biotic and abiotic stresses in the promoters of peanut SNARE genes. Transcriptomic data showed that expression of SNARE genes is tissue-specific and stress inducible. We hypothesize that AhVTI13b plays an important role in the storage of lipid proteins, while AhSYP122a, AhSNAP33a and AhVAMP721a might play an important role in development and stress responses. Furthermore, we showed that three AhSNARE genes (AhSYP122a, AhSNAP33a and AhVAMP721) enhance cold and NaCl tolerance in yeast (Saccharomyces cerevisiae), especially AhSNAP33a. This systematic study provides valuable information about the functional characteristics of AhSNARE genes in the development and regulation of abiotic stress responses in peanut.

Salt Stress Inhibits Photosynthesis and Destroys Chloroplast Structure by Downregulating Chloroplast Development-Related Genes in Robinia pseudoacacia Seedlings

Soil salinization is an important factor limiting food security and ecological stability. As a commonly used greening tree species, Robinia pseudoacacia often suffers from salt stress that can manifest as leaf yellowing, decreased photosynthesis, disintegrated chloroplasts, growth stagnation, and even death. To elucidate how salt stress decreases photosynthesis and damages photosynthetic structures, we treated R. pseudoacacia seedlings with different concentrations of NaCl (0, 50, 100, 150, and 200 mM) for 2 weeks and then measured their biomass, ion content, organic soluble substance content, reactive oxygen species (ROS) content, antioxidant enzyme activity, photosynthetic parameters, chloroplast ultrastructure, and chloroplast development-related gene expression. NaCl treatment significantly decreased biomass and photosynthetic parameters, but increased ion content, organic soluble substances, and ROS content. High NaCl concentrations (100-200 mM) also led to distorted chloroplasts, scattered and deformed grana lamellae, disintegrated thylakoid structures, irregularly swollen starch granules, and larger, more numerous lipid spheres. Compared to control (0 mM NaCl), the 50 mM NaCl treatment significantly increased antioxidant enzyme activity while upregulating the expression of the ion transport-related genes Na⁺/H⁺ exchanger 1(NHX 1) and salt overly sensitive 1 (SOS 1) and the chloroplast development-related genes psaA, psbA, psaB, psbD, psaC, psbC, ndhH, ndhE, rps7, and ropA. Additionally, high concentrations of NaCl (100-200 mM) decreased antioxidant enzyme activity and downregulated the expression of ion transport- and chloroplast development-related genes. These results showed that although R. pseudoacacia can tolerate low concentrations of NaCl, high concentrations (100-200 mM) can damage chloroplast structure and disturb metabolic processes by downregulating gene expression.

Selenium Regulates Antioxidant, Photosynthesis, and Cell Permeability in Plants under Various Abiotic Stresses: A Review

Plant growth is affected by various abiotic stresses, including water, temperature, light, salt, and heavy metals. Selenium (Se) is not an essential nutrient for plants but plays important roles in alleviating the abiotic stresses suffered by plants. This article summarizes the Se uptake and metabolic processes in plants and the functions of Se in response to water, temperature, light, salt, and heavy metal stresses in plants. Se promotes the uptake of beneficial substances, maintains the stability of plasma membranes, and enhances the activity of various antioxidant enzymes, thus alleviating adverse effects in plants under abiotic stresses. Future research directions on the relationship between Se and abiotic stresses in plants are proposed. This article will further deepen our understanding of the relationship between Se and plants.

Desaturases: Structural and mechanistic insights into the biosynthesis of unsaturated fatty acids

This review highlights the key role of fatty acid desaturases in the synthesis of naturally occurring, more common and not unsaturated fatty acids. The three major classes of fatty acid desaturases, such as acyl-lipid, acyl-acyl carrier protein and acyl-coenzyme A, are described in detail, with particular attention to the cellular localisation, the structure, the substrate and product specificity and the expression and regulation of desaturase genes. The review also gives an insight into the biocatalytic reaction of fatty acid desaturation by covering the general and more class-specific mechanistic studies around the synthesis of unsaturated fatty acids Finally, we conclude the review by looking at the numerous novel applications for desaturases in order to meet the very high demand for polyunsaturated fatty acids, taking into account the opportunity for the development of new, more efficient, easily reproducible, sustainable bioengineering advances in the field.

Identification and Investigation of the Genetic Variations and Candidate Genes Responsible for Seed Weight via GWAS in Paper Mulberry

Seeds directly determine the survival and population size of woody plants, but the genetic basis of seed weight in woody plants remain poorly explored. To identify genetic variations and candidate genes responsible for seed weight in natural woody populations, we investigated the hundred-seed weight of 198 paper mulberry individuals from different areas. Our results showed that the hundred-seed weight of paper mulberry was significantly associated with the bioclimatic variables of sampling sites, which increased from south to north along the latitudinal-temperature gradient. Using 2,414,978 high-quality SNPs from re-sequencing data, the genome-wide association analysis of the hundred-seed weight was performed under three models, which identified 148, 19 and 12 associated genes, respectively. Among them, 25 candidate genes were directly hit by the significant SNPs, including the WRKY transcription factor, fatty acid desaturase, F-box protein, etc. Most importantly, we identified three crucial genetic variations in the coding regions of candidate genes (Bp02g2123, Bp01g3291 and Bp10g1642), and significant differences in the hundred-seed weight were detected among the individuals carrying different genotypes. Further analysis revealed that Bp02g2123 encoding a fatty acid desaturase (FAD) might be a key factor affecting the seed weight and local climate adaptation of woody plants. Furthermore, the genome-wide investigation and expression analysis of FAD genes were performed, and the results suggested that BpFADs widely expressed in various tissues and responded to multiple phytohormone and stress treatments. Overall, our study identifies valuable genetic variations and candidate genes, and provides a better understanding of the genetic basis of seed weight in woody plants.

Genome-wide identification of biotin carboxyl carrier subunits of acetyl-CoA carboxylase in Brassica and their role in stress tolerance in oilseed Brassica napus

Background

Biotin carboxyl carrier protein (BCCP) is a subunit of Acetyl CoA-carboxylase (ACCase) which catalyzes the conversion of acetyl-CoA to malonyl-CoA in a committed step during the de novo biosynthesis of fatty acids. Lipids, lipid metabolites, lipid-metabolizing and -modifying enzymes are known to play a role in biotic and abiotic stress tolerance in plants. In this regard, an understanding of the Brassica napus BCCP genes will aid in the improvement of biotic and abiotic stress tolerance in canola.

Results

In this study, we identified 43 BCCP genes in five Brassica species based on published genome data. Among them, Brassica rapa, Brassica oleracea, Brassica nigra, Brassica napus and Brassica juncea had six, seven, seven, 10 and 13 BCCP homologs, respectively. Phylogenetic analysis categorized them into five classes, each with unique conserved domains. The promoter regions of all BCCP genes contained stress-related cis-acting elements as determined by cis-element analysis. We identified four and three duplicated gene pairs (segmental) in B. napus and B. juncea respectively, indicating the role of segmental duplication in the expansion of this gene family. The Ka/Ks ratios of orthologous gene pairs between Arabidopsis thaliana and five Brassica species were mostly less than 1.0, implying that purifying selection, i.e., selective removal of deleterious alleles, played a role during the evolution of Brassica genomes. Analysis of 10 BnaBCCP genes using qRT-PCR showed a different pattern of expression because of exposure of the plants to biotic stresses, such as clubroot and sclerotinia diseases, and abiotic stresses such as drought, low temperature and salinity stresses.

Conclusions

The identification and functional analysis of the Brassica BCCPs demonstrated that some of these genes might play important roles in biotic and abiotic stress responses. Results from this study could lay the foundation for a better understanding of these genes for the improvement of Brassica crops for stress tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08920-y.

Integrative System Biology Analysis of Transcriptomic Responses to Drought Stress in Soybean (Glycine max L.)

Drought is a major abiotic stressor that causes yield losses and limits the growing area for most crops. Soybeans are an important legume crop that is sensitive to water-deficit conditions and suffers heavy yield losses from drought stress. To improve drought-tolerant soybean cultivars through breeding, it is necessary to understand the mechanisms of drought tolerance in soybeans. In this study, we applied several transcriptome datasets obtained from soybean plants under drought stress in comparison to those grown under normal conditions to identify novel drought-responsive genes and their underlying molecular mechanisms. We found 2168 significant up/downregulated differentially expressed genes (DEGs) and 8 core modules using gene co-expression analysis to predict their biological roles in drought tolerance. Gene Ontology and KEGG analyses revealed key biological processes and metabolic pathways involved in drought tolerance, such as photosynthesis, glyceraldehyde-3-phosphate dehydrogenase and cytokinin dehydrogenase activity, and regulation of systemic acquired resistance. Genome-wide analysis of plants' cis-acting regulatory elements (CREs) and transcription factors (TFs) was performed for all of the identified DEG promoters in soybeans. Furthermore, the PPI network analysis revealed significant hub genes and the main transcription factors regulating the expression of drought-responsive genes in each module. Among the four modules associated with responses to drought stress, the results indicated that GLYMA_04G209700, GLYMA_02G204700, GLYMA_06G030500, GLYMA_01G215400, and GLYMA_09G225400 have high degrees of interconnection and, thus, could be considered as potential candidates for improving drought tolerance in soybeans. Taken together, these findings could lead to a better understanding of the mechanisms underlying drought responses in soybeans, which may useful for engineering drought tolerance in plants.

Genome-Wide Identification of Membrane-Bound Fatty Acid Desaturase Genes in Three Peanut Species and Their Expression in Arachis hypogaea during Drought Stress

As a crop irrigated primarily by rain, the quality and yield of peanuts are significantly limited by drought. To date, many studies have indicated that fatty acid desaturase (FAD) genes enhance plant tolerance to drought stresses. In this study, 16, 15, and 31 FADs were identified in Arachis duranensis, Arachis ipaensis, and Arachis hypogaea, respectively. All the FADs were divided into four subfamilies, which had relatively conserved gene structures, motifs, and domains. The synteny relationships and chromosomal position analysis showed that the FADs in subgenome pairs, A. duranensis-A. hypogaea (AA) and A. ipaensis-A. hypogaea (BB), were homologous, and their physical locations were consistent. The Ka/Ks results indicated that nine FAD genes underwent a purifying selection, and Ah|FAD3.2 experienced positive selection during tetraploid peanut speciation. Various cis-acting elements related to hormone signaling and stress responsiveness in promoters and the predicted miRNA targeting Ah|FADs suggested that these genes play crucial roles in drought tolerance. The expression profiles of Ah|FADs in 22 tissues and drought-tolerant and -sensitive cultivars under drought stress suggested that 4 and 6 FADs were putative genes related to oil accumulation and drought, respectively. These findings will help provide insight into the potential functional roles of the FAD genes, which may aid in dealing with plant drought stress.

Combined Proteomic and Metabolomic Analysis of the Molecular Mechanism Underlying the Response to Salt Stress during Seed Germination in Barley

Salt stress is a major abiotic stress factor affecting crop production, and understanding of the response mechanisms of seed germination to salt stress can help to improve crop tolerance and yield. The differences in regulatory pathways during germination in different salt-tolerant barley seeds are not clear. Therefore, this study investigated the responses of different salt-tolerant barley seeds during germination to salt stress at the proteomic and metabolic levels. To do so, the proteomics and metabolomics of two barley seeds with different salt tolerances were comprehensively examined. Through comparative proteomic analysis, 778 differentially expressed proteins were identified, of which 335 were upregulated and 443 were downregulated. These proteins, were mainly involved in signal transduction, propanoate metabolism, phenylpropanoid biosynthesis, plant hormones and cell wall stress. In addition, a total of 187 salt-regulated metabolites were identified in this research, which were mainly related to ABC transporters, amino acid metabolism, carbohydrate metabolism and lipid metabolism; 72 were increased and 112 were decreased. Compared with salt-sensitive materials, salt-tolerant materials responded more positively to salt stress at the protein and metabolic levels. Taken together, these results suggest that salt-tolerant germplasm may enhance resilience by repairing intracellular structures, promoting lipid metabolism and increasing osmotic metabolites. These data not only provide new ideas for how seeds respond to salt stress but also provide new directions for studying the molecular mechanisms and the metabolic homeostasis of seeds in the early stages of germination under abiotic stresses.

Mycorrhizal symbiosis reprograms ion fluxes and fatty acid metabolism in wild jujube during salt stress

Chinese jujube (Ziziphus jujuba) is an important fruit tree in China, and soil salinity is the main constraint affecting jujube production. It is unclear how arbuscular mycorrhizal (AM) symbiosis supports jujube adaptation to salt stress. Herein, we performed comparative physiological, ion flux, fatty acid (FA) metabolomic, and transcriptomic analyses to examine the mechanism of AM jujube responding to salt stress. AM seedlings showed better performance during salt stress. AM symbiosis altered phytohormonal levels: indole-3-acetic acid and abscisic acid contents were significantly increased in AM roots and reduced by salt stress. Mycorrhizal colonization enhanced root H+ efflux and K+ influx, while inducing expression of plasma membrane-type ATPase 7 (ZjAHA7) and high-affinity K+ transporter 2 (ZjHAK2) in roots. High K+/Na+ homeostasis was maintained throughout salt exposure. FA content was elevated in AM leaves as well as roots, especially for palmitic acid, oleic acid, trans oleic acid, and linoleic acid, and similar effects were also observed in AM poplar (Populus. alba × Populus. glandulosa cv. 84K) and Medicago truncatula, indicating AM symbiosis elevating FA levels could be a conserved physiological effect. Gene co-expression network analyses uncovered a core gene set including 267 genes in roots associated with AM symbiosis and conserved transcriptional responses, for example, FA metabolism, phytohormone signal transduction, SNARE interaction in vesicular transport, and biotin metabolism. In contrast to widely up-regulated genes related to FA metabolism in AM roots, limited genes were affected in leaves. We propose a model of AM symbiosis-linked reprogramming of FA metabolism and provide a comprehensive insight into AM symbiosis with a woody species adaptation to salt stress.

Salvianolic Acid Modulates Physiological Responses and Stress-Related Genes That Affect Osmotic Stress Tolerance in Glycine max and Zea mays

Drought is a serious threat worldwide to soybean and maize production. This study was conducted to discern the impact of salvianolic acid treatment on osmotic-stressed soybean (Glycine max L.) and maize (Zea mays L.) seedlings from the perspective of physiochemical and molecular reactions. Examination of varied salvianolic acid concentrations (0, 0.1, 1, 5, 10, and 25 μM) on soybean and maize seedling growth confirmed that the 0.1 and 1 μM concentrations, respectively, showed an improvement in agronomic traits. Likewise, the investigation ascertained how salvianolic acid application could retrieve osmotic-stressed plants. Soybean and maize seedlings were irrigated with water or 25% PEG for 8 days. The results indicated that salvianolic acid application promoted the survival of the 39-day-old osmotic-stressed soybean and maize plants. The salvianolic acid-treated plants retained high photosynthetic pigments, protein, amino acid, fatty acid, sugar, and antioxidant contents, and demonstrated low hydrogen peroxide and lipid contents under osmotic stress conditions. Gene transcription pattern certified that salvianolic acid application led to an increased expression of GmGOGAT, GmUBC2, ZmpsbA, ZmNAGK, ZmVPP1, and ZmSCE1d genes, and a diminished expression of GmMIPS2, GmSOG1, GmACS, GmCKX, ZmPIS, and ZmNAC48 genes. Together, our results indicate the utility of salvianolic acid to enhance the osmotic endurance of soybean and maize plants.

Can omic tools help generate alternative newer sources of edible seed oil?

There are three pathways for triacylglycerol (TAG) biosynthesis: De novo TAG biosynthesis, phosphatidylcholine-derived biosynthesis, and cytosolic TAG biosynthesis. Variability in fatty acid composition is mainly associated with phosphatidylcholine-derived TAG pathway. Mobilization of TAG-formed through cytosolic pathway into lipid droplets is yet unknown. There are multiple regulatory checkpoints starting from acetyl-CoA carboxylase to the lipid droplet biogenesis in TAG biosynthesis. Although a primary metabolism, only a few species synthesize oil in seeds for storage, and less than 10 species are commercially exploited. To meet out the growing demand for oil, diversifying into newer sources is the only choice left. The present review highlights the potential strategies targeting species like Azadirachta, Callophyllum, Madhuca, Moringa, Pongamia, Ricinus, and Simarouba, which are not being used for eating but are otherwise high yielding (ranging from 1.5 to 20 tons per hectare) with seeds having a high oil content (40-60%). Additionally, understanding the toxin biosynthesis in Ricinus and Simarouba would be useful in developing toxin-free oil plants. Realization of the importance of cell cultures as "oil factories" is not too far into the future and would soon be a commercially viable option for producing oils in vitro, round the clock.

Heterologous Expression of Arabidopsis AtARA6 in Soybean Enhances Salt Tolerance

Salt damage is an important abiotic stress affecting the agronomic traits of soybean. Soybeans rapidly sense and transmit adverse signals when salt-damaged, inducing a set of response mechanisms to resist salt stress. AtARA6 encodes a small GTPase, which plays an important role in Arabidopsis vesicle transport and salt tolerance. In this study, we transformed the Arabidopsis gene AtARA6 into the cultivated soybean Shen Nong 9 (SN9). To investigate the salt tolerance pathways affected by AtARA6 in soybean, we performed transcriptome sequencing using transgenic soybean and wild-type (SN9) under salt treatment and water treatment. Our results suggest that AtARA6 is involved in the regulation of soybean SNARE complexes in the vesicle transport pathway, which may directly strengthen salt tolerance. In addition, we comprehensively analyzed the RNA-seq data of transgenic soybean and SN9 under different treatments and obtained 935 DEGs. GO analysis showed that these DEGs were significantly enriched in transcription factor activity, sequence-specific DNA binding, and the inositol catabolic process. Three salt-responsive negative regulator transcription factors, namely MYC2, WRKY6, and WRKY86, were found to be significantly downregulated after salt treatment in transgenic soybeans. Moreover, four genes encoding inositol oxygenase were significantly enriched in the inositol catabolic process pathway, which could improve the salt tolerance of transgenic soybeans by reducing their reactive oxygen species content. These are unique salt tolerance effects produced by transgenic soybeans. Our results provide basic insights into the function of AtARA6 in soybeans and its role in abiotic stress processes in plants.

Ser/Thr Protein Kinase SpkI Affects Photosynthetic Efficiency in Synechocystis sp. PCC 6803 upon Salt Stress

High salinity is a common environmental factor that limits productivity and growth for photosynthetic organisms. Here, we identified a mutant defected in gene sll1770, which encodes a Ser/Thr protein kinase SpkI, with a significantly low maximal quantum yield of PSII under high salt condition in Synechocystis sp. PCC 6803. Physiological characterization demonstrated that the ΔspkI mutant had normal growth and photosynthesis under control condition. And a significantly higher NPQ capacity was also observed in ΔspkI when grown under control condition. However, when grown under high salt condition, ΔspkI exhibited apparently slower growth as well as decreased net photosynthesis and PSII activity. Western blot analysis demonstrated that the amount of major photosynthetic proteins declined sharply in ΔspkI when cells grown under high salt condition. Redox kinetics measurement suggested that the activities of PSI and cytochrome b₆f complex were modified in ΔspkI under high salt condition, which resulted in a more reduced PQ pool in ΔspkI. Chlorophyll fluorescence traces suggested that the O_A⁻ reoxidation and state transition was also impaired in ΔspkI under high salt condition. Above all, we propose that Ser/Thr protein kinase SpkI plays a role in maintaining high-effective photosynthesis during high-salt acclimation process in Synechocystis.

Linkage and association analyses reveal that hub genes in energy-flow and lipid biosynthesis pathways form a cluster in upland cotton

Upland cotton is an important allotetraploid crop that provides both natural fiber for the textile industry and edible vegetable oil for the food or feed industry. To better understand the genetic mechanism that regulates the biosynthesis of storage oil in cottonseed, we identified the genes harbored in the major quantitative trait loci/nucleotides (QTLs/QTNs) of kernel oil content (KOC) in cottonseed via both multiple linkage analyses and genome-wide association studies (GWAS). In ‘CCRI70′ RILs, six stable QTLs were simultaneously identified by linkage analysis of CHIP and SLAF-seq strategies. In ‘0-153′ RILs, eight stable QTLs were detected by consensus linkage analysis integrating multiple strategies. In the natural panel, thirteen and eight loci were associated across multiple environments with two algorithms of GWAS. Within the confidence interval of a major common QTL on chromosome 3, six genes were identified as participating in the interaction network highly correlated with cottonseed KOC. Further observations of gene differential expression showed that four of the genes, LtnD, PGK, LPLAT1, and PAH2, formed hub genes and two of them, FER and RAV1, formed the key genes in the interaction network. Sequence variations in the coding regions of LtnD, FER, PGK, LPLAT1, and PAH2 genes may support their regulatory effects on oil accumulation in mature cottonseed. Taken together, clustering of the hub genes in the lipid biosynthesis interaction network provides new insights to understanding the mechanism of fatty acid biosynthesis and TAG assembly and to further genetic improvement projects for the KOC in cottonseeds.

Soil Amendment with Arbuscular Mycorrhizal Fungi and Biochar Improves Salinity Tolerance, Growth, and Lipid Metabolism of Common Wheat (Triticum aestivum L.)

Salt stress in soils impacts grain crop yield. Soil amendment with biochar and arbuscular mycorrhizal alone has been analyzed to improve the growth of several crops under salinity stress. However, the combined application of biochar and arbuscular mycorrhizal fungi for the remediation of salinity and improvement of crop productivity in wheat are rarely discussed and have remained unclear. Therefore, this experiment was performed to investigate the effect with biochar (150 g biochar per each treated pot containing 3 kg soil) and/or arbuscular mycorrhizal fungi (20 g AMF inoculum containing 80% mycorrhizal roots, 100–160 spores, and extraradical hyphae per each treated pot) on the productivity of wheat (Triticum aestivum L.) under four salt stress gradients; 0, 50, 100, and 150 mM NaCl. The results show salinity significantly reduced plant height (9.9% to 22.9%), shoot fresh weight (35.6% to 64.4%), enzymatic activities (34.1% to 39.3%), and photosynthetic pigments—i.e., total chlorophyll contents (75.0%) and carotenoids contents (56.2%) of plants—as compared with control. Under exclusive biochar application, the plants were moderately tolerant to salinity stress, which was evident in their growth, moderately reduced fatty acid content, partially impaired enzymatic activity, and photosynthetic pigments, while under the exclusive AMF application, the wheat plants were relatively sensitive to salinity stress, resulting in impaired growth rate, decreased unsaturated fatty acid composition, enzymatic activity, and photosynthetic pigments. Conversely, under the co-application of biochar and AMF, wheat plants partially increased plant height (14.1%), shoot fresh biomass (75.7%), root fresh biomass (24.9%), partially increased enzymatic activity (49.5%), and unimpaired photosynthetic pigments (30.2% to 54.8%) of wheat under salinity stress. Current findings concluded that exclusive incorporation of biochar, and the synergistic application of AMF and biochar, could be utilized as a promising way to reduce the deleterious effects of salinity stress in wheat production.

Label-free proteomics approach reveals candidate proteins in rice (Oryza sativa L.) important for ACC deaminase producing bacteria-mediated tolerance against salt stress

The omics-based studies are important for identifying characteristic proteins in plants to elucidate the mechanism of ACC deaminase producing bacteria-mediated salt tolerance. This study evaluates the changes in the proteome of rice inoculated with ACC deaminase producing bacteria under salt stress conditions. Salt stress resulted in a significant decrease in photosynthetic pigments, whereas inoculation of Methylobacterium oryzae CBMB20 had significantly increased pigment contents under normal and salt stress conditions. A total of 76, 51 and 33 differentially abundant proteins (DAPs) were identified in non-inoculated salt stressed plants, bacteria inoculated plants under normal and salt stress conditions, respectively. The abundances of proteins responsible for ethylene emission and programmed cell death were increased, and that of photosynthesis-related proteins were decreased in non-inoculated plants under salt stress. Whereas, bacteria-inoculated plants had shown higher abundance of antioxidant proteins, RuBisCo and ribosomal proteins that are important for enhancing stress tolerance and improving plant physiological traits. Collectively, salt stress might affect plant physiological traits by impairing photosynthetic machinery and accelerating apoptosis leading to a decline in biomass. However, inoculation of plants with bacteria can assist in enhancing photosynthetic activity, antioxidant activities and ethylene regulation related proteins for attenuating salt induced apoptosis and sustaining growth and development. This article is protected by copyright. All rights reserved.

Long-distance control of pumpkin rootstock over cucumber scion under drought stress as revealed by transcriptome sequencing and mobile mRNAs identifications

Grafting with pumpkin rootstock is commonly used not only to improve the quality of cucumber fruits but also to confer biotic or abiotic stress tolerance. However, the molecular mechanism of grafted cucumbers to drought stress and the possible roles of mobile mRNAs to improve stress tolerance have remained obscure. Hence, we conducted transcriptome sequencing and combined it with morpho-physiological experiments to compare the response of homografts (cucumber as scion and rootstock) (C) and heterografts (cucumber as scion and pumpkin as rootstock) (P) to drought stress. After applying drought stress, homografts and heterografts expressed 2960 and 3088 genes in response to drought stress, respectively. The identified DEGs in heterografts under drought stress were categorized into different stress-responsive groups, such as carbohydrate metabolism (involved in osmotic adjustment by sugar accumulation), lipid and cell wall metabolism (involved in cell membrane integrity by a reduction in lipid peroxidation), redox homeostasis (increased antioxidant enzymes activities), phytohormone (increased ABA content), protein kinases and transcription factors (TFs) using MapMan software. Earlier and greater H2O2 accumulation in xylem below the graft union was accompanied by leaf ABA accumulation in heterografts in response to drought stress. Greater leaf ABA helped heterografted cucumbers to sense and respond to drought stress earlier than homografts. The timely response of heterografts to drought stress led to maintain higher water content in the leaves even in the late stage of drought stress. The identified mobile mRNAs (mb-mRNAs) in heterografts were mostly related to photosynthesis which would be the possible reason for improved chlorophyll content and maximum photochemical efficiency of PSII (Fv/Fm). The existence of some stress-responsive pumpkin (rootstock) mRNAs in cucumber (scion), such as heat shock protein (HSP70, a well-known stress-responsive gene), led to the higher proline accumulation than homografts. The expression of the mobile and immobile stress-responsive mRNAs and timely response of heterografts to drought stress could improve drought tolerance in pumpkin-rooted plants.

Differential Physio-Biochemical and Metabolic Responses of Peanut (Arachis hypogaea L.) under Multiple Abiotic Stress Conditions

The frequency and severity of extreme climatic conditions such as drought, salinity, cold, and heat are increasing due to climate change. Moreover, in the field, plants are affected by multiple abiotic stresses simultaneously or sequentially. Thus, it is imperative to compare the effects of stress combinations on crop plants relative to individual stresses. This study investigated the differential regulation of physio-biochemical and metabolomics parameters in peanut (Arachis hypogaea L.) under individual (salt, drought, cold, and heat) and combined stress treatments using multivariate correlation analysis. The results showed that combined heat, salt, and drought stress compounds the stress effect of individual stresses. Combined stresses that included heat had the highest electrolyte leakage and lowest relative water content. Lipid peroxidation and chlorophyll contents did not significantly change under combined stresses. Biochemical parameters, such as free amino acids, polyphenol, starch, and sugars, significantly changed under combined stresses compared to individual stresses. Free amino acids increased under combined stresses that included heat; starch, sugars, and polyphenols increased under combined stresses that included drought; proline concentration increased under combined stresses that included salt. Metabolomics data that were obtained under different individual and combined stresses can be used to identify molecular phenotypes that are involved in the acclimation response of plants under changing abiotic stress conditions. Peanut metabolomics identified 160 metabolites, including amino acids, sugars, sugar alcohols, organic acids, fatty acids, sugar acids, and other organic compounds. Pathway enrichment analysis revealed that abiotic stresses significantly affected amino acid, amino sugar, and sugar metabolism. The stress treatments affected the metabolites that were associated with the tricarboxylic acid (TCA) and urea cycles and associated amino acid biosynthesis pathway intermediates. Principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), and heatmap analysis identified potential marker metabolites (pinitol, malic acid, and xylopyranose) that were associated with abiotic stress combinations, which could be used in breeding efforts to develop peanut cultivars that are resilient to climate change. The study will also facilitate researchers to explore different stress indicators to identify resistant cultivars for future crop improvement programs.

Exogenous hesperidin and chlorogenic acid alleviate oxidative damage induced by arsenic toxicity in Zea mays through regulating the water status, antioxidant capacity, redox balance and fatty acid composition

Arsenic (As) toxicity is a problem that needs to be solved in terms of both human health and agricultural production in the vast majority of the world. The presence of As causes biomass loss by disrupting the balance of biochemical processes in plants and preventing growth/water absorption in the roots and accumulating in the edible parts of the plant and entering the food chain. A critical method of combating As toxicity is the use of biosafe, natural, bioactive compounds such as hesperidin (HP) or chlorogenic acid (CA). To this end, in this study, the physiological and biochemical effects of HP (100 μM) and CA (50 μM) were investigated in Zea mays under arsenate stress (100 μM). Relative water content, osmotic potential, photosynthesis-related parameters were suppressed under stress. It was determined that stress decreased the activities of the antioxidant system and increased the level of saturated fatty acids and, gene expression of PHT transporters involved in the uptake and translocation of arsenate. After being exposed to stress, HP and CA improved the capacity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), glutathione S-transferase (GST) and glutathione peroxidase (GPX) and then ROS accumulation (H₂O₂) and lipid peroxidation (TBARS) were effectively removed. These phenolic compounds contributed to maintaining the cellular redox status by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. HP and CA reversed the adverse effects of excessive metal ion accumulation by re-regulated expression of the PHT1.1 and PHT1.3 genes in response to stress. Exogenously applied HP and CA effectively maintained membrane integrity by regulating saturated/unsaturated fatty acid content. However, the combined application of HP and CA did not show a synergistic protective activity against As stress and had a negative effect on the antioxidant capacity of maize leaves. As a result, HP and CA have great potentials to provide tolerance to maize under As stress by reducing oxidative injury and preserving the biochemical reactions of photosynthesis.

Defective cytokinin signaling reprograms lipid and flavonoid gene-to-metabolite networks to mitigate high salinity in Arabidopsis

Cytokinin (CK) in plants regulates both developmental processes and adaptation to environmental stresses. Arabidopsis histidine phosphotransfer ahp2,3,5 and type-B Arabidopsis response regulator arr1,10,12 triple mutants are almost completely defective in CK signaling, and the ahp2,3,5 mutant was reported to be salt tolerant. Here, we demonstrate that the arr1,10,12 mutant is also more tolerant to salt stress than wild-type (WT) plants. A comprehensive metabolite profiling coupled with transcriptome analysis of the ahp2,3,5 and arr1,10,12 mutants was conducted to elucidate the salt tolerance mechanisms mediated by CK signaling. Numerous primary (e.g., sugars, amino acids, and lipids) and secondary (e.g., flavonoids and sterols) metabolites accumulated in these mutants under nonsaline and saline conditions, suggesting that both prestress and poststress accumulations of stress-related metabolites contribute to improved salt tolerance in CK-signaling mutants. Specifically, the levels of sugars (e.g., trehalose and galactinol), amino acids (e.g., branched-chain amino acids and γ-aminobutyric acid), anthocyanins, sterols, and unsaturated triacylglycerols were higher in the mutant plants than in WT plants. Notably, the reprograming of flavonoid and lipid pools was highly coordinated and concomitant with the changes in transcriptional levels, indicating that these metabolic pathways are transcriptionally regulated by CK signaling. The discovery of the regulatory role of CK signaling on membrane lipid reprogramming provides a greater understanding of CK-mediated salt tolerance in plants. This knowledge will contribute to the development of salt-tolerant crops with the ability to withstand salinity as a key driver to ensure global food security in the era of climate crisis.

The potential of prodigiosin for control of Prorocentrum donghaiense blooms: Algicidal properties and acute toxicity to other marine organisms at various trophic levels

Prorocentrum donghaiense, a marine dinoflagellate, causes harmful algal blooms (HABs) characterised by the highest outbreak frequency and most extensive coverage among similar species in the East China Sea. Highly efficient and ecofriendly biocontrol strategies should be developed for HAB control. Prodigiosin is an efficient biological algicide that demonstrated strong algicidal activity towards P. donghaiense. However, the mechanism of its toxicity to P. donghaiense is unknown. These factors were investigated to evaluate potential use of prodigiosin for control of P. donghaiense blooms. Photosynthetic electron transport rate, maximum quantum yield and respiration rate of P. donghaiense decreased significantly upon exposure to prodigiosin, indicating that prodigiosin rapidly exerted adverse effects on the chloroplasts and mitochondria. Furthermore, a significant increase in dichlorofluorescein fluorescence intensity indicated an overproduction of reactive oxygen species (ROS). The antioxidant system of P. donghaiense scavenged ROS; however, an increase in malondialdehyde concentrations indicated that excessive ROS were still able to initiate lipid peroxidation. Thus, ROS production resulted in the formation of lipids with a reduced degree of unsaturation. Lipid peroxidation decreased lipid fluidity and rigidified the membrane system, causing serious functional destruction of the membrane. Flow cytometry analysis indicated that prodigiosin arrested the cell cycle of P. donghaiense. However, surviving algal cells were able to repair the damaged functions and resume the cell cycle after prodigiosin was removed by photodegradation. Otherwise, P. donghaiense cells lost their membrane integrity and died. To begin an evaluation of ecological safety of prodigiosin, we tested four marine organisms at various trophic levels. The results of these tests indicated that Chlorella vulgaris, Photobacterium phosphoreum, Artemia salina and Lateolabrax japonicus were less sensitive to prodigiosin than P. donghaiense. Toxicity to all five organisms declined after prodigiosin was exposed to sunlight for 6 h. Considering the toxic doses of prodigiosin to various organisms and its photodegradation characteristics, we suggest that prodigiosin has potential in controlling P. donghaiense blooms but should be applied at night, in small doses, with multiple applications.

Metabolomics and Physiological Insights into the Ability of Exogenously Applied Chlorogenic Acid and Hesperidin to Modulate Salt Stress in Lettuce Distinctively

Recent studies in the agronomic field indicate that the exogenous application of polyphenols can provide tolerance against various stresses in plants. However, the molecular processes underlying stress mitigation remain unclear, and little is known about the impact of exogenously applied phenolics, especially in combination with salinity. In this work, the impacts of exogenously applied chlorogenic acid (CA), hesperidin (HES), and their combination (HES + CA) have been investigated in lettuce (Lactuca sativa L.) through untargeted metabolomics to evaluate mitigation effects against salinity. Growth parameters, physiological measurements, leaf relative water content, and osmotic potential as well as gas exchange parameters were also measured. As expected, salinity produced a significant decline in the physiological and biochemical parameters of lettuce. However, the treatments with exogenous phenolics, particularly HES and HES + CA, allowed lettuce to cope with salt stress condition. Interestingly, the treatments triggered a broad metabolic reprogramming that involved secondary metabolism and small molecules such as electron carriers, enzyme cofactors, and vitamins. Under salinity conditions, CA and HES + CA distinctively elicited secondary metabolism, nitrogen-containing compounds, osmoprotectants, and polyamines.

The Roles of CCCH Zinc-Finger Proteins in Plant Abiotic Stress Tolerance

Zinc-finger proteins, a superfamily of proteins with a typical structural domain that coordinates a zinc ion and binds nucleic acids, participate in the regulation of growth, development, and stress adaptation in plants. Most zinc fingers are C2H2-type or CCCC-type, named after the configuration of cysteine (C) and histidine (H); the less-common CCCH zinc-finger proteins are important in the regulation of plant stress responses. In this review, we introduce the domain structures, classification, and subcellular localization of CCCH zinc-finger proteins in plants and discuss their functions in transcriptional and post-transcriptional regulation via interactions with DNA, RNA, and other proteins. We describe the functions of CCCH zinc-finger proteins in plant development and tolerance to abiotic stresses such as salt, drought, flooding, cold temperatures and oxidative stress. Finally, we summarize the signal transduction pathways and regulatory networks of CCCH zinc-finger proteins in their responses to abiotic stress. CCCH zinc-finger proteins regulate the adaptation of plants to abiotic stress in various ways, but the specific molecular mechanisms need to be further explored, along with other mechanisms such as cytoplasm-to-nucleus shuttling and post-transcriptional regulation. Unraveling the molecular mechanisms by which CCCH zinc-finger proteins improve stress tolerance will facilitate the breeding and genetic engineering of crops with improved traits.

Mechanisms and functions of membrane lipid remodeling in plants

Lipid remodeling, defined herein as post-synthetic structural modifications of membrane lipids, play crucial roles in regulating the physicochemical properties of cellular membranes and hence their many functions. Processes affected by lipid remodeling include lipid metabolism, membrane repair, cellular homeostasis, fatty acid trafficking, cellular signaling and stress tolerance. Glycerolipids are the major structural components of cellular membranes and their composition can be adjusted by modifying their head groups, their acyl chain lengths and the number and position of double bonds. This review summarizes recent advances in our understanding of mechanisms of membrane lipid remodeling with emphasis on the lipases and acyltransferases involved in the modification of phosphatidylcholine and monogalactosyldiacylglycerol, the major membrane lipids of extraplastidic and photosynthetic membranes, respectively. We also discuss the role of triacylglycerol metabolism in membrane acyl chain remodeling. Finally, we discuss emerging data concerning the functional roles of glycerolipid remodeling in plant stress responses. Illustrating the molecular basis of lipid remodeling may lead to novel strategies for crop improvement and other biotechnological applications such as bioenergy production.

Genome-wide association mapping of sodium and potassium concentration in rice grains and shoots under alternate wetting and drying and continuously flooded irrigation

Identification of a large number of QTL and candidate genes for sodium accumulation in a field grown population of rice derived from the aus subpopulation. Rice (Oryza sativa L.) is a globally important cereal crop. Sodium (Na⁺) and potassium (K⁺) are the major monovalent ions which affect rice growth, and exploring their uptake mechanisms will be useful for understanding rice biology. Since the balance of Na⁺ and K⁺ plays a significant role in adaptation of rice to salinity, that biology might inform the search for tolerance. In this study, the Na⁺ and K⁺ concentration and Na⁺/K⁺ ratio in grains and shoots were analyzed in the Bengal and Assam Aus Panel grown in field conditions under continuously flooded (CF) and alternate wetting and drying (AWD) irrigation. Overall, AWD irrigation significantly reduced the Na⁺ concentration and increased the K⁺ concentration in shoots and grains compared to the plants grown under CF. Genome-wide association mapping was conducted on Na⁺, K⁺ concentration and Na⁺/K⁺ ratio with 2 million SNPs using an efficient mixed model. Only QTLs which contained more than two significant SNPs (p < 0.0001) and where at least one of these significant SNPs passed a 10% false discovery rate were reported. A total of 106 QTLs were identified as being associated with Na⁺ concentration and Na⁺/K⁺ ratio across all traits and field conditions, with 48 QTLs found in multiple traits and/or water conditions. Four notable QTLs (one each on chromosomes 1 and 11, two on chromosome 2) and the haplotype variants of four candidate genes (OsHKT1;5, OsNHX2, LOC_Os02g32490 and OsFAD2_1) are discussed. The QTLs/candidate genes identified here could be useful for breeding rice that accumulates lower concentrations of sodium.

Comprehensive transcriptional analysis reveals salt stress-regulated key pathways, hub genes and time-specific responsive gene categories in common bermudagrass (Cynodon dactylon (L.) Pers.) roots

BACKGROUND

Despite its good salt-tolerance level, key genes and pathways involved with temporal salt response of common bermudagrass (Cynodon dactylon (L.) Pers.) have not been explored. Therefore, in this study, to understand the underlying regulatory mechanism following the different period of salt exposure, a comprehensive transcriptome analysis of the bermudagrass roots was conducted.

RESULTS

The transcripts regulated after 1 h, 6 h, or 24 h of hydroponic exposure to 200 mM NaCl in the roots of bermudagrass were investigated. Dataset series analysis revealed 16 distinct temporal salt-responsive expression profiles. Enrichment analysis identified potentially important salt responsive genes belonging to specific categories, such as hormonal metabolism, secondary metabolism, misc., cell wall, transcription factors and genes encoded a series of transporters. Weighted gene co-expression network analysis (WGCNA) revealed that lavenderblush2 and brown4 modules were significantly positively correlated with the proline content and peroxidase activity and hub genes within these two modules were further determined. Besides, after 1 h of salt treatment, genes belonging to categories such as signalling receptor kinase, transcription factors, tetrapyrrole synthesis and lipid metabolism were immediately and exclusively up-enriched compared to the subsequent time points, which indicated fast-acting and immediate physiological responses. Genes involved in secondary metabolite biosynthesis such as simple phenols, glucosinolates, isoflavones and tocopherol biosynthesis were exclusively up-regulated after 24 h of salt treatment, suggesting a slightly slower reaction of metabolic adjustment.

CONCLUSION

Here, we revealed salt-responsive genes belonging to categories that were commonly or differentially expressed in short-term salt stress, suggesting possible adaptive salt response mechanisms in roots. Also, the distinctive salt-response pathways and potential salt-tolerant hub genes investigated can provide useful future references to explore the molecular mechanisms of bermudagrass.

Analysis of N6-methyladenosine reveals a new important mechanism regulating the salt tolerance of sweet sorghum

The N⁶-methyladenosine (m⁶A) modification is the most common internal post-transcriptional modification, with important regulatory effects on RNA export, splicing, stability, and translation. Studies on the m⁶A modifications in plants have focused on Arabidopsis thaliana growth and development. However, A. thaliana is a salt-sensitive and model plant species. Thus, studies aimed at characterizing the role of the m⁶A modification in the salt stress responses of highly salt-tolerant crop species are needed. Sweet sorghum is cultivated as an energy and forage crop, which is highly suitable for growth on saline-alkaline land. Exploring the m⁶A modification in sweet sorghum may be important for elucidating the salt-resistance mechanism of crops. In this study, we mapped the m⁶A modifications in two sorghum genotypes (salt-tolerant M-81E and salt-sensitive Roma) that differ regarding salt tolerance. The m⁶A modification in sweet sorghum under salt stress was drastically altered, especially in Roma, where the m⁶A modification on mRNAs of some salt-resistant related transcripts increased, resulting in enhanced mRNA stability, which in turn was involved in the regulation of salt tolerance in sweet sorghum. Although m⁶A modifications are important for regulating sweet sorghum salt tolerance, the regulatory activity is limited by the initial m⁶A modification level. Additionally, in M-81E and Roma, the differences in the m⁶A modifications were much greater than the differences in gene expression levels and are more sensitive. Our study suggests that the number and extent of m⁶A modifications on the transcripts of salt-resistance genes may be important factors for determining and assessing the salt tolerance of crops.

Plant growth-promoting microbes — an industry view

Plant growth-promoting microbes can affect the plant microbiome, improving different properties of the plant such as yield and health. Many companies are commercializing these microbes as products called biologicals. Defining the product concept is one of the first and most important steps in making a biological product. Companies can use phenotyping and genotyping approaches to identify the microbe to make into a live bacterial product. Screening usually begins in the laboratory and often moves from high-throughput methods to more time and resource-intensive methods culminating in large scale field testing. Once the microbe is chosen, the fermentation process grows the bacteria to the necessary amounts, while the formulation process ensures a stable product in the desired form such as a liquid or powder. The products must show yield increases in the field over several seasons and conditions, but also must be easy to use and cost-effective to be adopted by farmers and other customers. Tying all these data together from the selection process to test results gives a customer a ‘reason to believe’ for the marketing and launch of a successful product.

Transcriptomic analysis reveals potential pathways associated with salt resistance in pecan (Carya illinoensis K. Koch)

Soil salinity is a serious abiotic stress worldwide. Pecan plants (Carya illinoensis K. Koch) have been suggested for cultivation in soils with high levels of salinity owing to their huge demand. To understand the potential molecular mechanisms in pecan in response to salt stress, RNA-sequencing technology was used to compare the transcriptomes of pecan plants treated with 0, 0.3 %, or 0.6 % NaCl solutions. The results indicated that 170,086 unigenes were obtained from pecan leaf cDNA samples. Based on the assembled de novo transcriptome, 53, 535, and 7358 differentially expressed genes (DEGs) were detected between untreated and salt-treated leaves at 8, 24, and 48 h, respectively. Because of the large number of DEGs across different contrasts, a Gene Set Enrichment Analysis was selected to identify gene pathways associated with salt treatment. A total of 1858 DEGs were enriched in 66 gene sets, including 22 up-regulated and 47 down-regulated gene sets in the salt treatment groups, compared with those in the control groups. The up-regulated gene sets were mainly involved in the response to salicylic acid; the regulation of the jasmonic acid-mediated signalling pathway during the short-term treatment (8 h); and the cellular response to hypoxia, cellular respiration, and RNA modification during the long-term treatment (24-48 h). The down-regulated gene sets were predominately associated with photosynthesis, water transport, and the metabolic biosynthetic process under salt stress. Genes related to the Really Interesting New Gene superfamily protein and F-box domain protein in the ubiquitin-dependent degradation pathway were significantly up-regulated or down-regulated in different periods of the regulating process. Overall, these results not only enrich genomic resources but also provide insights into the molecular mechanism in pecan under salt stress.

An insight into the role of silicon on retaliation to osmotic stress in finger millet (Eleusine coracana (L.) Gaertn)

Finger millet, a vital nutritional cereal crop provides food security. It is a well-established fact that silicon (Si) supplementation to plants alleviates both biotic and abiotic stresses. However, precise molecular targets of Si remain elusive. The present study attempts to understand the alterations in the metabolic pathways after Si amendment under osmotic stress. The analysis of transcriptome and metabolome of finger millet seedlings treated with distilled water (DW) as control, Si (10 ppm), PEG (15%), and PEG (15%) + Si (10 ppm) suggest the molecular alterations mediated by Si for ameliorating the osmotic stress. Under osmotic stress, uptake of Si has increased mediating the diversion of an enhanced pool of acetyl CoA to lipid biosynthesis and down-regulation of TCA catabolism. The membrane lipid damage reduced significantly by Si under osmotic stress. A significant decrease in linolenic acid and an increase of jasmonic acid (JA) in PEG + Si treatment suggest the JA mediated regulation of osmotic stress. The relative expression of transcripts corroborated with the corresponding metabolites abundance levels indicating the activity of genes in assuaging the osmotic stress. This work substantiates the role of Si in osmotic stress tolerance by reprogramming of fatty acids biosynthesis in finger millet.

Integration of miRNAs, Degradome, and Transcriptome Omics Uncovers a Complex Regulatory Network and Provides Insights Into Lipid and Fatty Acid Synthesis During Sesame Seed Development

Sesame (Sesamum indicum L.) has always been known as a health-promoting oilseed crop because of its nutrient-rich oil. In recent years, studies have focused on lipid and fatty acid (FA) biosynthesis in various plants by high-throughput sequencing. Here, we integrated transcriptomics, small RNAs, and the degradome to establish a comprehensive reserve intensive on key regulatory micro RNA (miRNA)-targeting circuits to better understand the transcriptional and translational regulation of the oil biosynthesis mechanism in sesame seed development. Deep sequencing was performed to differentially express 220 miRNAs, including 65 novel miRNAs, in different developmental periods of seeds. GO and integrated KEGG analysis revealed 32 pairs of miRNA targets with negatively correlated expression profiles, of which 12 miRNA-target pairs were further confirmed by RT-PCR. In addition, a regulatory co-expression network was constructed based on the differentially expressed gene (DEG) profiles. The FAD2, LOC10515945, LOC105161564, and LOC105162196 genes were clustered into groups that regulate the accumulation of unsaturated fatty acid (UFA) biosynthesis. The results provide a unique advanced molecular platform for the study of lipid and FA biosynthesis, and this study may serve as a new theoretical reference to obtain increased levels of UFA from higher-quality sesame seed cultivars and other plants.

AhABI4s Negatively Regulate Salt-Stress Response in Peanut

Soil salinity is one of the major factors that limit the area of cultivable land and yield potential of crops. The ability of salt tolerance varies with plant species. Peanut (Arachis hypogaea L.) is a moderately salt-sensitive and economically important crop, however, their biological processes involved in salt-stress response remain unclear. In this study, we investigated the role of A. hypogaea L. ABSCISIC ACID INSENSITIVE 4s (AhABI4s) in salt tolerance and elucidated its mode of action in peanuts. The results showed that the downregulation of AhABI4s via whole plant virus-induced gene silencing has enhanced the survival rate, biomass accumulation, and root/shoot ratio of peanut seedlings in response to salt-stress. Transcriptomics, quantitative proteomics, and phosphoproteomic analyses were performed using AhABI4s-silenced and Mock plants. The expression pattern of 15,247 genes, 1,900 proteins, and 2,620 phosphorylation sites were affected by silencing of AhABI4s in peanut leaf and root after sodium chloride (NaCl) treatment. Among them, 63 potential downstream target genes of ABI4 changed consistently at both transcription and translation levels, and the protein/phosphorylation levels of 31 ion transporters/channels were also affected. Electrophoretic mobility shift assays (EMSA) showed that ABI4 was able to bind to the promoters of HSP70, fructokinase (FRK), and pyruvate kinase (PK) coding genes in vitro. In addition, we also detected a binding preference of AhABI4 for CACT(G/T)GCA motif in the promoters of down-regulated genes in peanut leaf. Collectively, the potential downstream targets which were regulated at the levels of transcription and translation, binding preference, and in vivo phosphorylation sites that had been revealed in this study will provide new insight into the AhABI4s-mediated salt tolerance regulation mechanism in peanuts.

Drought and Salinity Stress Responses and Microbe-Induced Tolerance in Plants

Drought and salinity are among the most important environmental factors that hampered agricultural productivity worldwide. Both stresses can induce several morphological, physiological, biochemical, and metabolic alterations through various mechanisms, eventually influencing plant growth, development, and productivity. The responses of plants to these stress conditions are highly complex and depend on other factors, such as the species and genotype, plant age and size, the rate of progression as well as the intensity and duration of the stresses. These factors have a strong effect on plant response and define whether mitigation processes related to acclimation will occur or not. In this review, we summarize how drought and salinity extensively affect plant growth in agriculture ecosystems. In particular, we focus on the morphological, physiological, biochemical, and metabolic responses of plants to these stresses. Moreover, we discuss mechanisms underlying plant-microbe interactions that confer abiotic stress tolerance.

Respiratory Burst Oxidase Homologs RBOHD and RBOHF as Key Modulating Components of Response in Turnip Mosaic Virus-Arabidopsis thaliana (L.) Heyhn System

Turnip mosaic virus (TuMV) is one of the most important plant viruses worldwide. It has a very wide host range infecting at least 318 species in over 43 families, such as Brassicaceae, Fabaceae, Asteraceae, or Chenopodiaceae from dicotyledons. Plant NADPH oxidases, the respiratory burst oxidase homologues (RBOHs), are a major source of reactive oxygen species (ROS) during plant–microbe interactions. The functions of RBOHs in different plant–pathogen interactions have been analyzed using knockout mutants, but little focus has been given to plant–virus responses. Therefore, in this work we tested the response after mechanical inoculation with TuMV in ArabidopsisrbohD and rbohF transposon knockout mutants and analyzed ultrastructural changes after TuMV inoculation. The development of the TuMV infection cycle was promoted in rbohD plants, suggesting that RbohD plays a role in the Arabidopsis resistance response to TuMV. rbohF and rbohD/F mutants display less TuMV accumulation and a lack of virus cytoplasmic inclusions were observed; these observations suggest that RbohF promotes viral replication and increases susceptibility to TuMV. rbohD/F displayed a reduction in H₂O₂ but enhanced resistance similarly to rbohF. This dominant effect of the rbohF mutation could indicate that RbohF acts as a susceptibility factor. Induction of hydrogen peroxide by TuMV was partially compromised in rbohD mutants whereas it was almost completely abolished in rbohD/F, indicating that these oxidases are responsible for most of the ROS produced in this interaction. The pattern of in situ H₂O₂ deposition after infection of the more resistant rbohF and rbohD/F genotypes suggests a putative role of these species on systemic signal transport. The ultrastructural localization and quantification of pathogenesis-related protein 1 (PR1) indicate that ROS produced by these oxidases also influence PR1 distribution in the TuMV-A.thaliana pathosystem. Our results revealed the highest activation of PR1 in rbohD and Col-0. Thus, our findings indicate a correlation between PR1 accumulation and susceptibility to TuMV. The specific localization of PR1 in the most resistant genotypes after TuMV inoculation may indicate a connection of PR1 induction with susceptibility, which may be characteristic for this pathosystem. Our results clearly indicate the importance of NADPH oxidases RbohD and RbohF in the regulation of the TuMV infection cycle in Arabidopsis. These findings may help provide a better understanding of the mechanisms modulating A.thaliana–TuMV interactions.

Current Advances in Plant Growth Promoting Bacteria Alleviating Salt Stress for Sustainable Agriculture

Humanity in the modern world is confronted with diverse problems at several levels. The environmental concern is probably the most important as it threatens different ecosystems, food, and farming as well as humans, animals, and plants. More specifically, salinization of agricultural soils is a global concern because of on one side, the permanent increase of the areas affected, and on the other side, the disastrous damage caused to various plants affecting hugely crop productivity and yields. Currently, great attention is directed towards the use of Plant Growth Promoting Bacteria (PGPB). This alternative method, which is healthy, safe, and ecological, seems to be very promising in terms of simultaneous salinity alleviation and improving crop productivity. This review attempts to deal with different aspects of the current advances concerning the use of PGPBs for saline stress alleviation. The objective is to explain, discuss, and present the current progress in this area of research. We firstly discuss the implication of PGPB on soil desalinization. We present the impacts of salinity on crops. We look for the different salinity origin and its impacts on plants. We discuss the impacts of salinity on soil. Then, we review various recent progress of hemophilic PGPB for sustainable agriculture. We categorize the mechanisms of PGPB toward salinity tolerance. We discuss the use of PGPB inoculants under salinity that can reduce chemical fertilization. Finally, we present some possible directions for future investigation. It seems that PGPBs use for saline stress alleviation gain more importance, investigations, and applications. Regarding the complexity of the mechanisms implicated in this domain, various aspects remain to be elucidated.

Green leaf volatile (Z)-3-hexeny-1-yl acetate reduces salt stress in peanut by affecting photosynthesis and cellular redox homeostasis

Green leaf volatiles (GLVs) are released by plants when they encounter biotic stress, but their functions in the response to abiotic stress have not been determined. We have previously shown that exogenous application of (Z)-3-hexeny-1-yl acetate (Z-3-HAC), a kind of GLV, could alleviate salt stress in peanut (Arachis hypogaea L.) seedlings; however, notably little is known concerning the transcription regulation mechanisms of Z-3-HAC. In this study, we comprehensively characterized the transcriptomes and physiological indices of peanut seedlings exposed to Z-3-HAC and/or salt stress. Analysis of transcriptome data showed that 1420 genes were upregulated in the seedlings primed with Z-3-HAC under salt stress compared with the non-primed treatment. Interestingly, these genes were significantly enriched in the photosynthetic and ascorbate metabolism-related categories, as well as several plant hormone metabolism pathways. The physiological data revealed that Z-3-HAC significantly increased the net photosynthetic rate, SPAD value, plant height and shoot biomass compared with the non-primed peanut seedlings under salt stress. A significantly higher ratio of K⁺ :Na⁺ , reduced-to-oxidized glutathione (GSH:GSSG), and ascorbate-to-dehydroascorbate (AsA:DHA) were also observed for the plants primed with Z-3-HAC compared with the salt stress control. Meanwhile, Z-3-HAC significantly increased the activity of enzymes in the AsA-GSH cycle. Taken together, these results highlight the importance of Z-3-HAC in protecting peanut seedlings against salt stress by affecting photosynthesis, cellular redox homeostasis, K⁺ :Na⁺ homeostasis, and phytohormones.

Edible Plant Oil: Global Status, Health Issues, and Perspectives

Edible plant oil (EPO) is an indispensable nutritional resource for human health. Various cultivars of oil-bearing plants are grown worldwide, and the chemical compositions of different plant oils are diverse. The extremely complex components in oils lead to diverse standards for evaluating the quality and safety of different EPOs. The environment poses great challenges to the EPO safety and quality during the entire industrial chain, including plant cultivation, harvesting, oil processing, and storage. Environmental risk factors include heavy metal or pesticide residue pollution, insect or harmful microbial infestation, and rancidity. Here, the diverse components in oil and various oil-producing processes are discussed, including plant species, oil yield, and composition complexity, environmental factors that degrade oil quality. Additionally, we propose a whole-industrial-chain monitoring system instead of current single-link-monitoring approach by monitoring and tracking the quality and safety of EPOs during the entire process of plant cultivation, raw materials harvest, oil process, and EPOs storage. This will provide guidance for monitoring the quality and safety of EPOs, which were challenged by the deteriorating environment.

Unraveling the mechanisms of resistance to Sclerotium rolfsii in peanut (Arachis hypogaea L.) using comparative RNA-Seq analysis of resistant and susceptible genotypes

Stem rot, a devastating fungal disease of peanut, is caused by Sclerotium rolfsii. RNA-sequencing approaches have been used to unravel the mechanisms of resistance to stem rot in peanut over the course of fungal infection in resistant (NRCG-CS85) and susceptible (TG37A) genotypes under control conditions and during the course of infection. Out of about 290 million reads, nearly 251 million (92.22%) high-quality reads were obtained and aligned to the Arachis duranensis and Arachis ipaensis genomes with the average mapping of 78.91% and 78.61%, respectively. In total, about 48.6% of genes were commonly regulated, while approximately 21.8% and 29.6% of uniquely regulated genes from A. duranensis and A. ipaensis genomes, respectively, were identified. Several annotated transcripts, such as receptor-like kinases, jasmonic acid pathway enzymes, and transcription factors (TFs), including WRKY, Zinc finger protein, and C2-H2 zinc finger, showed higher expression in resistant genotypes upon infection. These transcripts have a known role in channelizing the downstream of pathogen perception. The higher expression of WRKY transcripts might have induced the systemic acquired resistance (SAR) by the activation of the jasmonic acid defense signaling pathway. Furthermore, a set of 30 transcripts involved in the defense mechanisms were validated with quantitative real-time PCR. This study suggested PAMP-triggered immunity as a probable mechanism of resistance, while the jasmonic acid signaling pathway was identified as a possible defense mechanism in peanut. The information generated is of immense importance in developing more effective ways to combat the stem rot disease in peanut.

Selenium mitigates salt-induced oxidative stress in durum wheat (Triticum durum Desf.) seedlings by modulating chlorophyll fluorescence, osmolyte accumulation, and antioxidant system

Hydroponic experiments were conducted to investigate the effects of different concentrations of sodium selenate (Na₂SeO₄) and sodium selenite (Na₂SeO₃) on durum wheat seed germination and seedling growth under salt stress. The treatments used were 0 and 50 mM NaCl solutions, each supplemented with Na₂SeO₄ or Na₂SeO₃ at 0, 0.1, 1, 2, 4, 8, or 10 μM. Salt alone significantly inhibited seed germination and reduced seedling growth. Addition of low concentrations (0.1-4 μM) of Na₂SeO₄ or Na₂SeO₃ mitigated the adverse effects of salt stress on seed germination, biomass accumulation, and other physiological attributes. Among them, 1 μM Na₂SeO₄ was most effective at restoring seed germination rate, germination energy, and germination index, significantly increasing these parameters by about 12.35, 24.17, and 11.42%, respectively, compared to salt-stress conditions. Adding low concentrations of Na₂SeO₄ or Na₂SeO₃ to the salt solution also had positive effects on chlorophyll fluorescence indices, decreased the concentrations of free proline and malondialdehyde, as well as electrolyte leakage, and increased catalase, superoxide dismutase, and peroxidase activities in roots and shoots. However, high concentrations (8-10 μM) of Na₂SeO₄ or Na₂SeO₃ disrupted seed germination and seedling growth, with damage caused by Na₂SeO₃ being more severe than that by Na₂SeO₄. It is thus clear that exogenous selenium can improve the adaptability of processing wheat to salt stress and maintain higher photosynthetic rate by decreasing the accumulation of reactive oxygen species and alleviating the degree of membrane lipid peroxidation. Na₂SeO₄ was more effective than Na₂SeO₃ at all given concentrations.