Search

Recently, we reported the discovery of a novel endoglucanase of the glycoside hydrolase family 12 (GH12), designated IfCelS12A, from the haloalkaliphilic anaerobic bacterium Iocasia fonsfrigidae strain SP3-1, which was isolated from a hypersaline pond in the Samut Sakhon province of Thailand (ca. 2017). IfCelS12A exhibits high substrate specificity on carboxymethyl cellulose and amorphous cellulose but low substrate specificity on b-1,3;1,4-glucan. Unlike some endoglucanases of the GH12 family, IfCelS12A does not exhibit hydrolytic activity on crystalline cellulose (i.e., Avicel™). High-Pressure Liquid Chromatography (HPLC) and Thin Layer Chromatography (TLC) analyses of products resulting from IfCelS12-mediated hydrolysis indicate mode of action for this enzyme. Notably, IfCelS12A preferentially hydrolyzes cellotetraoses, cellopentaoses, and cellohexaoses with negligible activity on cellobiose or cellotriose. Kinetic analysis with cellopentaose and barely b-D-glucan as cellulosic substrates were conducted. On cellopentaose, IfCelS12A demonstrates a 16-fold increase in activity (KM = 0.27 mM; kcat = 0.36 s-1; kcat/KM = 1.34 mM-1 s-1) compared to the enzymatic hydrolysis of barley b-D-glucan (KM: 0.04 mM, kcat: 0.51 s-1, kcat/KM = 0.08 mM-1 s-1). Moreover, IfCelS12A enzymatic efficacy is stable in hypersaline sodium chlorids (NaCl) solutions (up to 10% NaCl). Specifically, IfCel12A retains notable activity after 24 h at 2M NaCl (10% saline solution). IfCelS12A used as a cocktail component with other cellulolytic enzymes and in conjunction with mobile sequestration platform technology offers additional options for deconstruction of ionic liquid-pretreated cellulosic feedstock. KEY POINTS: • IfCelS12A from an anaerobic alkaliphile Iocasia fronsfrigidae shows salt tolerance • IfCelS12A in cocktails with other enzymes efficiently degrades cellulosic biomass • IfCelS12A used with mobile enzyme sequestration platforms enhances hydrolysis.

Chloride (Cl−) ions cause major damage to crops in saline soils. Understanding the key factors that influence Cl− uptake and translocation will aid the breeding of more salt-tolerant crops. Here, using genome-wide association study and transcriptomic analysis, we identified a NITRATE TRANSPORTER 1 (NRT1)/PEPTIDE TRANSPORTER family (NPF) protein, GmNPF7.5, as the dominant gene locus influencing Cl− homeostasis in soybean (Glycine max). A natural SNP variation resulted in two haplotypes (GmNPF7.5HapA and GmNPF7.5HapB), which was associated with Cl− content. GmNPF7.5HapA mediated Cl− or nitrate (NO3−) uptake in a pH-dependent manner and exhibited higher permeability for Cl− over NO3−. The suppression of GmNPF7.5HapA expression decreased Cl− accumulation and salt damage in plants, whereas its overexpression showed the opposite effects. The elite haplotype GmNPF7.5HapB diminished Cl− transport activity independently from NO3− permeability, thus enhancing soybean salt tolerance. Furthermore, the protein kinase GmPI4Kγ4 could phosphorylate GmNPF7.5, which repressed Cl− uptake without affecting NO3− permeability. Our findings define a regulatory mechanism for Cl− control under NaCl stress, providing a strategy for the improvement of salt tolerance in soybean plants. Synopsis: Chloride ions are important inducers of salt toxicity in soybean plants. This study identifies GmNPF7.5 as a major contributor to chloride accumulation, and suppressing its expression leads to increased salt tolerance in commercial soybean cultivars. GmNPF7.5 mediates chloride and nitrate ion uptake in soybean. Salt stress induces the expression of GmPI4Kγ4 and enhances the interaction between GmPI4Kγ4 and GmNPF7.5. GmPI4Kγ4 phosphorylates GmNPF7.5 and inhibits its Cl– transport activity, thereby decreasing Cl– accumulation under salt stress. GmPI4Kγ4 acts as a protein kinase by phosphorylating nitrate transporter family protein GmNPF7.5, thus leading to the inhibition of chloride uptake under salt stress. [ABSTRACT FROM AUTHOR]

The development of a salt-tolerant hexaploid triticale cultivar offers an economical and efficient solution for utilizing marginal land. Understanding how hexaploid triticales respond to salt stress is essential if this goal is to be achieved. A genome-wide association study (GWAS), along with transcriptome and proteome analyses, were used in the present study to determine the molecular responses to salt stress in hexaploid triticale. In total, 81 marker-trait associations for 10 salt-tolerance traits were identified in 153 hexaploid triticale accessions, explaining 0.71% to 56.98% of the phenotypic variation, and 54 GWAS-associated genes were uncovered. A total of 67, 88, and 688 differential expression genes were co-expressed at both the transcriptomic and proteomic levels after 4, 12, and 18 h of salt stress, respectively. Among these differentially expressed genes, six appeared in the coincident expression trends for both the transcriptomic and proteomic levels at the seed germination stage. A total of nine common KEGG pathways were enriched at both the transcriptomic and proteomic levels at 4, 12, and 18 h. After integrating GWAS-target genes with transcriptomics and proteomics approaches that the candidate gene late embryogenesis abundant protein 14 (LEA14) was up-regulated at the transcriptomic and proteomic levels. LEA14 contained important stress-responsive cis-acting regulatory elements that could be dynamically regulated by the binding of transcription factors (TFs). This suggested that LEA14 was a key gene associated with salt tolerance in hexaploid triticale and could respond quickly to salt stress. This study improved understanding about the potential molecular mechanisms associated with hexaploid triticale salt tolerance and contributed to the breeding of salt-tolerant germplasms and the utilization of saline soils. [ABSTRACT FROM AUTHOR]

Calmodulin, a highly conserved calcium‐binding protein, plays a crucial role in response to salt stress. Previous studies investigated sequence and function of calmodulin members in some plants, but their roles in rice have not been fully elucidated. Three OsCaM1 genes namely OsCaM1‐1/2/3 encode the same OsCaM1 protein. Here, we found that OsCaM1‐1 had significantly higher expression than the other two genes under salt stress. After 4 weeks of exposure to 75 mM NaCl, OsCaM1‐1 overexpressed mutants showed higher salt tolerance, while knocked‐out mutants exhibited lower salt tolerance, compared to the wild type. Moreover, the oscam1‐1 mutants had higher Na+ concentration and Na+/K+ ratio in both shoots and roots, less instantaneous K+ and Ca2+ fluxes in roots, compared to wild type under salt stress, indicating the involvement of OsCaM1‐1 in regulation of Na+ and K+ homoeostasis via Ca2+ signal. RNA‐seq analysis identified 452 differentially expressed genes (DEGs) regulated by OsCaM1‐1 and salt stress, and they were mainly enriched in nucleus DNA‐binding activities, including ABI5, WRKY76, WRKY48 and bHLH120 transcription factors. Knockout of OsCaM1‐1 also modulated the expression of Na+ transporters, including HKT1;1, HKT1;5, SOS1, NHX1 and NHX4. In conclusion, OsCaM1‐1 positively regulates salt tolerance in rice through mediating ion homoeostasis. Summary statement: Calmodulin plays a crucial role in response to salt stress. Knockout of OsCaM1‐1 modulated the expressions of HKT1;5, HKT1;1, NHX1 and SOS1, highlighting the positive role of OsCaM1‐1 in the regulation of salt tolerance in rice through mediating ion homoeostasis. [ABSTRACT FROM AUTHOR]

Culturing saline tilapia has become a new trend in the aquaculture due to the scarcity of freshwater resources. In this study, the genetic basis controlling for salt tolerance were investigated by using a ddRAD-seq-based GWAS in 288 individuals with extreme salt tolerant traits from half-sib families of red tilapia. 12 genome-wide significant SNPs and 6 chromosome-wide significant SNPs associated with acute salt tolerance were identified. Two QTLs on LG18:25,593,701–7009020 and on LG16:19,735,164–21,231,391 were defined. It is noteworthy that the QTL on LG16 is a novel QTL associated with acute salt stress. Near the significant SNP sites, we identified candidate genes sik1, ltb4r2b, pnp5b and kirrel1b with differential transcript expression under salt stress. Furthermore, significant physiological differences in serum osmolality and ion concentrations were confirmed between the tolerant group and sensitive group under 4.5 h of 22 ppt stress. The sensitive group had much higher serum osmolality (osmolality: 642.20 ± 6.30 mOsm/kg) and higher concentrations of sodium and chloride ions (sodium: 317.67 ± 5.03 mmol/L and chloride: 316.43 ± 8.28 mmol/L) than the tolerant group (547.60 ± 15.44 mOsm/kg, posmolality = 0.0002; sodium: 280.53 ± 9.13 mmol/L, psodium < 0.0242; chloride: 266.00 ± 12.00 mmol/L, pchloride < 0.0184). However, the lowest bicarbonate concentration was detected in the sensitive group at 22 ppt (2.53 ± 0.30 mmol/L), which was significantly different from both the sensitive group at 0 ppt (p = 0.0008) and the tolerant group at 22 ppt (p = 0.0164). Our research laid the foundation for exploring the genetic mechanisms of acute salt tolerance and osmoregulation in red tilapia and for developing strains of red tilapia adapted to saltwater. [ABSTRACT FROM AUTHOR]

Soil salinity is a major global challenge affecting agricultural productivity and food security. This study explores innovative strategies to improve salt tolerance in soybean (Glycine max), a crucial crop in the global food supply. This study investigates the synergistic effects of S-nitroso glutathione (GSNO) and silicon on enhancing salt tolerance in soybean (Glycine max). Two soybean cultivars, Seonpung (salt-tolerant) and Cheongja (salt-sensitive), were analyzed for various physiological, biochemical, and genetic traits under salt stress. The results showed that the combined GSNO and Si treatment significantly improved several key traits, including plant height, relative water content, root development, nodule numbers, chlorophyll content, and stomatal aperture, under both control and salt stress conditions. Additionally, this treatment optimized ion homeostasis by enhancing the Na/K ratio and Ca content, while reducing damage markers such as electrolyte leakage, malondialdehyde, and hydrogen peroxide. The stress-responsive compounds, including proline, ascorbate peroxidase, and water-soluble proteins, were elevated under stress conditions, indicating improved tolerance. Gene expression analysis revealed significant upregulation of genes such as GmNHX1, GmSOS2, and GmAKT1, associated with salt stress response, while GmNIP2.1, GmNIP2.2, and GmLBR were downregulated in both varieties. Notably, the salt-sensitive variety Cheongja exhibited higher electrolyte leakage and oxidative damage compared to the salt-tolerant Seonpung. These findings suggest that the combination of GSNO and silicon enhances salt tolerance in soybean by improving physiological resilience, ion homeostasis, and stress-responsive gene expression. [ABSTRACT FROM AUTHOR]

Background: Improving the germination performance of bread wheat is an important breeding target in many wheat-growing countries where seedlings are often established in soils with high salinity levels. This study sought to characterize the molecular mechanisms underlying germination performance in salt-stressed wheat. To achieve this goal, a genome-wide association study (GWAS) was performed on 292 Iranian bread wheat accessions, including 202 landraces and 90 cultivars. Results: A total of 10 and 15 functional marker-trait associations (MTAs) were detected under moderate (60 mM NaCl) and severe (120 mM NaCl) salinity, respectively. From genomic annotation, 17 candidate genes were identified that were functionally annotated to be involved in the germination performance of salt-stressed wheat, such as CHX2, PK2, PUBs, and NTP10. Most of these genes play key roles in DNA/RNA/ATP/protein binding, transferase activity, transportation, phosphorylation, or ubiquitination and some harbored unknown functions that collectively may respond to salinity as a complex network. Conclusion: These findings, including the candidate genes, respective pathways, marker-trait associations (MTAs), and in-depth phenotyping of wheat accessions, improve knowledge of the mechanisms responsible for better germination performance of wheat seedlings under salinity conditions. [ABSTRACT FROM AUTHOR]

Hybrid rice typically surpasses conventional rice in terms of biomass, yield, and stress resistance, whereas developing and utilizing saline–alkali-tolerant hybrid rice is crucial to obtain crop harvests from salt-affected soils. In the present study, conventional rice varieties (paternal parents), i.e., Hua-Zhan and 9311, and four hybrid varieties, i.e., Xiang-Liang-You-Hua-Zhan, Jing-Liang-You-Hua-Zhan, Guang-8-You-Hua-Zhan, and Y-Liang-You-1-Hao, denoted as V1, V2, V3, V4, V5, and V6, respectively, received an application of two salt levels, i.e., 0% and 0.3% saltwater irrigation, during 2022–2023. The results reveal that the V1 (parental parent) had the highest salt tolerance index, which was significantly greater than that of its hybrid rice varieties, i.e., V3, V4, and V5. Moreover, the salt tolerance index of V2 (paternal parent) was also greater than that of its hybrid rice (V6). The lower salt tolerance index of the hybrid varieties might be owing to the lower relative loss number of effective panicles, total number of grains per panicle, seed setting rate, and thousand-grain weight. Moreover, our study revealed that the appearance of different rice varieties was enhanced at a salt concentration of 0.3%. Among all the rice cultivars, the largest reductions in chalkiness and chalky grain rate were observed in hybrid rice V3, i.e., 81.13% and 63.49%, as well as V6, i.e., 84.03% and 87.53%, respectively. The protein and sodium contents and sodium-potassium ratio of all the rice cultivars increased significantly under salt stress; however, no significant effect on cooking or sensory quality were noticed in all rice varieties under saline conditions. Overall, salt stress negatively affected the grain yield and quality, but hybrid rice is more salt-tolerant than conventional rice, harnessing heterosis to improve the yield of saline-tolerant rice. [ABSTRACT FROM AUTHOR]

In order to explore the effects of different mixed salt stress on germination of dandelion (Taraxacum mongolicum Hand-Mazz) seeds, in this study, dandelion seeds were used as experimental materials, and four mixed salts composed of different concentrations of NaCl (pH=7.20), Na2SO4 (pH=8.03), NaHCO3 (pH=8.90), and Na2CO3 (pH=9.63) were prepared. The concentration ratios of the four salts in the mixed salt were 1∶1∶0∶0 (YA), 1∶2∶1∶0 (YB), 1∶9∶9∶1 (YC), and 1: 1∶1∶1 (YD), respectively. Five concentration gradients (25, 50 100 150, and 200 mmol/L) were set for each mixed salt, and distilled water was used as the control (CK). Different types of mixed salt solutions were used to simulate the mixed saline-alkali soil conditions for the saline-alkali stress treatment of dandelion seeds, and germination and variation of dandelion seeds under alkaline salt stress were analyzed. The results showed that germination of most seeds was negatively affected to a certain extent under mixed salt stress. Under the same mixed salt, the germination rate of seeds decreased significantly with the increase of salt concentration. When the concentration of the four mixed salts was 25 mmol/L, the seed recovery germination rate was higher after rehydration, and the final germination rate was not significantly different from that of CK. At the same pH value, both the recovery germination rate and the final germination rate decreased to varying degrees with the increase of salt stress concentration. [ABSTRACT FROM AUTHOR]

Soil salinity is a significant abiotic factor that impedes sustainable crop production in key agricultural regions worldwide. Saline cultivation adversely affects soil quality, whereas the use of saline water for irrigation disrupts the physiological and biochemical processes of plants. Continuous irrigation with high salt concentrations leads to a gradual buildup of soil salinity, thus hindering optimal plant growth and development. Consequently, there is a growing emphasis on breeding salinity-tolerant cultivars of various crops. In this study, 71 tomato accessions sourced from 20 countries and provided by the US Department of Agriculture were evaluated under controlled greenhouse conditions and subjected to saline stress (200 mM NaCl). The experiment used a split-plot design, with the salt treatment serving as the main plot and the tomato accession as the subplot, which were arranged in a completely randomized design with three replications. Results identified nine accessions (PI 109837, PI 127820, PI 270256, PI 634828, PI 636205, PI 636255, PI 647143, PI 647528, and PI 647556) as salt-tolerant. Additionally, high broad-sense heritability was observed for the leaf injury score and leaf chlorophyll content. Furthermore, positive correlations were found among parameters related to the leaf injury score and leaf chlorophyll content (soil plant analysis development value). These findings offer valuable insights for tomato breeding programs, particularly those focused on enhancing salt tolerance of elite cultivars of this crucial crop. [ABSTRACT FROM AUTHOR]

Key message: SlNAC12 enhances salt stress tolerance of transgenic tomato by regulating ion homeostasis, antioxidant activity and flavonoids biosynthesis Soil salinization is a major environmental factor that adversely affects plant growth and development. NAC (NAM, ATAF1/2, and CUC2) is a large family of plant-specific transcription factors that play crucial roles in stress response. Here, we investigated the role of a novel NAC transcription factor, SlNAC12, in conferring salt stress tolerance in tomato (Solanum lycopersicum). Subcellular localization and yeast assays studies revealed that SlNAC12 is localized in the nucleus with weak transcriptional activity. SlNAC12 transcript was induced by salt stress in the leaves and roots of tomato seedlings. Overexpression of SlNAC12 in tomato led to significantly reduced plant height and root length. Transgenic tomato lines overexpressing of SlNAC12 (OE#1 and OE#3) exhibited enhanced tolerance to salinity, as evidenced by reduced the inhibitory effect of growth parameters under salt stress compared to wild type (WT). Overexpression of SlNAC12 in tomato affected Na+ and K+ homeostasis, leading to reduced Na+/K+ ratio, enhanced activity of antioxidant enzymes and decreased reactive oxygen species (ROS) accumulation under salt stress. Furthermore, the transcript levels of several genes involved in flavonoids metabolism and the levels of flavonoids accumulation were increased in SlNAC12-overexpressing tomato lines. Collectively, this study suggests that SlNAC12 transcription factor enhances salt stress tolerance in tomato is correlated with ion homeostasis, antioxidant enzyme systems, and flavonoids accumulation. [ABSTRACT FROM AUTHOR]

Key message: All ten dehydrin genes from three Medicago species are responsive to different kinds of abiotic stress, and CAS31 confers transgenic plants salt tolerance by down-regulating HKT1 expression. Dehydrins are protective proteins playing crucial roles in the tolerance of plants to abiotic stresses. However, a full-scale and systemic analysis of total dehydrin genes in Medicago at the genome level is still lacking. In this study, we identified ten dehydrin genes from three Medicago species (M. truncatula, M. ruthenica, and M. sativa), categorizing the coding proteins into four types. Genome collinearity analysis among the three Medicago species revealed six orthologous gene pairs. Promoter regions of dehydrin genes contained various phytohormone- and stress-related cis-elements, and transcriptome analysis showed up-regulation of all ten dehydrin genes under different stress conditions. Transformation of dehydrin gene CAS31 increased the tolerance of transgenic seedlings compared with wild-type seedlings under salt stress. Our study demonstrated that transgenic seedlings maintained the more chlorophyll, accumulated more proline and less hydrogen peroxide and malondialdehyde than wild-type seedlings under salt stress. Further study revealed that CAS31 reduced Na+ accumulation by down-regulating HKT1 expression under salt stress. These findings enhance our understanding of the dehydrin gene family in three Medicago species and provide insights into their mechanisms of tolerance. [ABSTRACT FROM AUTHOR]

Key message: Identification of salt-responsive calcineurin B-like protein-interacting protein kinases (CIPKs) in Populus. Calcineurin B-like protein-interacting protein kinases (CIPKs) play vital roles in plant growth and abiotic stress responses. Currently, the regulatory mechanisms underlying these processes mediated by CIPK proteins are not completely understood in woody species. This study provided the first systematic analysis of 31 Populus CIPK genes and investigated their evolutionary relationships, gene structures, motif compositions, and salt stress responses. A total of 11 pairs of paralogous PtCIPK genes were identified, of which three pairs may be resulted from whole genome duplication, and two pairs that may be created by tandem duplications. RT-qPCR analysis revealed that 93.5% (29/31) genes showed altered expression levels in roots after salt treatment. Ectopic expression of PdCIPK21 or PdCIPK31 in Arabidopsis resulted in significant increases of seed germination, root elongation and fresh weight under salt stress conditions. Cytological observation revealed that PdCIPK21/31 overexpression lines showed increased number, lumen area and cell wall thickness of xylem vessels, and higher lignin content in stems compared with the wild type, with decreased sensitivity to long-term salt stress treatment. Our results suggest that PdCIPK21/31 serve as candidate genes for improving wood production and enhancing salt tolerance of tree species. [ABSTRACT FROM AUTHOR]

Tetraploid plants always exhibit noticeable changes in tissue structure and stress tolerance, but the underlying physiological mechanisms remain poorly understood. Here, we generated a tetraploid plant of Populus davidiana using colchicine induction and performed phenotypic characterization. The results showed that the tetraploid plant had bigger ground diameters and leaf area than the diploid plant. The tetraploid plant had thicker palisade tissue but less stomatal density than the diploid plant. The tetraploid plant also had higher chlorophyll content, net photosynthetic rate, maximal efficiency of PSII photochemistry, the effective quantum yield of PSII, photochemical quenching coefficient but lower non-photochemical quenching coefficient than the diploid plant. Furthermore, we found that the tetraploid plant displayed significantly enhanced drought and salt tolerance in comparison with the diploid progenitor. Our results not only revealed the structural and physiological changes in the tetraploid plant, but also provided a reference for the generation of better quality varieties.Key message: In this study, a tetraploid poplar was obtained and phenotypic analysis revealed the structural and physiological changes of tetraploid poplar compared with its diploid ancestor. [ABSTRACT FROM AUTHOR]

For plant diseases to become established, plant pathogens require not only virulence factors and susceptible hosts, but also optimal environmental conditions. The accumulation of high soil salinity can have serious impacts on agro-biological ecosystems. However, the interactions between plant pathogens and salinity have not been fully characterized. This study investigated the effects of salt stress on representative plant pathogens, such as Burkholderia gladioli, Burkholderia glumae, Pectobacterium carotovorum subsp. carotovorum (Pcc), Ralstonia solanacearum, and Xanthomonas oryzae pv. oryzae. Phenotypic assays revealed that B. gladioli and R. solanacearum are highly sensitive to salt stress, exhibiting significant reductions in growth, motility, and enzyme production, whereas Pcc showed notable tolerance. Pan-genome-based comparative transcriptomics identified co-downregulated patterns in B. gladioli and R. solanacearum under stress conditions, indicating the suppression of bacterial chemotaxis and type III secretion systems. Uniquely upregulated patterns in Pcc were associated with enhanced survival under high salinity, such as protein quality control, osmotic equilibrium, and iron acquisition. Additionally, the application of salt stress combined with the beneficial bacterium Chryseobacterium salivictor significantly reduced tomato wilt caused by R. solanacearum, suggesting a potential management strategy. This study underscores practical implications for effectively understanding and controlling plant pathogens under future climate changes involving salt stress. [ABSTRACT FROM AUTHOR]

Salt stress poses a significant constraint on rice production, so further exploration is imperative to elucidate the intricate molecular mechanisms governing salt tolerance in rice. By manipulating the rhizosphere microbial communities or targeting specific microbial functions, it is possible to enhance salt tolerance in crops, improving crop yields and food security in saline environments. In this study, we conducted rice rhizospheric microbial amplicon sequencing and metatranscriptome analysis, revealing substantial microbiomic differences between the salt-tolerant rice cultivar TLJIAN and the salt-sensitive HUAJING. Fungal taxa including Hormiactis, Emericellopsis, Ceriosporopsis, Dirkmeia, and Moesziomyces predominated in the rhizosphere of salt-tolerant rice, while bacterial genera such as Desulfoprunum and Hydrogenophaga exhibited notable differences. Metatranscriptomic analysis identified 7192 differentially expressed genes (DEGs) in the two rice varieties, with 3934 genes being upregulated and 3258 genes being downregulated. Enrichment analyses in KEGG and GO pathways highlighted the majority of DEGs were associated with the "two-component system", "sulfur metabolism", and "microbial metabolism in diverse environments". The interaction network of DEGs and microbial taxa revealed upregulation of transporters, transcriptional factors, and chaperones, such as ABC transporters and chaperonin GroEL, in the rhizosphere microbiomes of salt-tolerant varieties. Our multi-omics network analysis unveiled that fungi like Ceriosporopsis and Dirkmeria, along with bacteria such as Desulfoprunum, Rippkaea, and Bellilinea, showed a positive correlation with flavonoid synthesis in salt-tolerant rice. This study provides an in-depth exploration of the distinctive microbial communities associated with the rhizosphere of salt-tolerant rice varieties, shedding light on the complex interactions between these microbial consortia and their host plants under stress conditions. [ABSTRACT FROM AUTHOR]

Dunaliella salina is an important source of natural β-carotene (containing 9-cis and all trans isomers) for industrial production. The phytohormone salicylic acid (SA) has been proven to have impacts on the stress resistance of higher plants, but research on microalgae is currently unclear. In this study, the effects of SA on the growth, biochemical composition, antioxidant enzyme activity, key enzymes of β-carotene synthesis, and cis-and trans-isomers of β-carotene in D. salina under different salt concentrations were investigated. The results were shown that at concentrations of 1.5, 2, and 2.5 M NaCl, the antioxidant enzyme activity and key enzymes for β-carotene synthesis in algal cells were significantly increased, but the content and proportion of 9-cis isomer in β-carotene isomers decreased. The addition of SA significantly increased the growth and antioxidant enzyme (SOD, MDA) activity, as well as the synthesis of key enzyme phytoene synthase (PSY), phytoene desaturase (PDS), and lycopene β cyclase (LCYB) of D. salina under high-salinity conditions. It is worth noting that under the treatment of SA, the proportion of 9-cis isomer in the three salt concentrations (1.5, 2, 2.5 M NaCl) significantly increased by 32.09%, 20.30%, and 11.32%, respectively. Moreover, SA can not only improve the salt tolerance of D. salina, but also increase the proportion of 9-cis isomer, with higher physiological activity in β-carotene, thereby enhancing the application value of D. salina. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Perennial ryegrass (Lolium perenne) is a widely cultivated forage and turf grass species. Salt stress can severely damage the growth of grass plants. The genome-wide molecular mechanisms of salt tolerance have not been well understood in perennial grass species. In this study, the salt sensitive genotype P1 (PI265351, Chile) and the salt tolerant genotype P2 (PI368892, Algeria) of perennial ryegrass were subjected to 200 mM NaCl, and transcriptomics and metabolomics analyses were performed. A total of 5,728 differentially expressed genes (DEGs) were identified through pairwise comparisons. Antioxidant enzyme encoding genes (LpSOD1, LpCAT1), ion channel gene LpCaC1 and transcription factors (LpERFs, LpHSF1 and LpMYB1) were significantly upregulated in P2, suggesting their involvement in regulating expression of salt-responsive genes for salt tolerance. Functional analysis of DEGs revealed that biosynthesis of secondary metabolites, carbohydrate metabolism and signal transduction were the main pathways in response to salt stress. Weighted gene co-expression network analysis (WGCNA) based on RNA-Seq data showed that membrane transport and ABC transporters were significantly correlated with salt tolerance-related traits. The combined transcriptomics and metabolomics analysis demonstrated that the phenylpropanoid biosynthesis pathway was a major secondary metabolic pathway in the salt response of perennial ryegrass. Especially, the tolerant genotype P2 had greater amounts of upregulated phenylpropanoids, flavonoids and anthocyanins and higher expressions of relevant genes in the pathway than the sensitive genotype P1, indicating a role of phenylpropanoid biosynthesis for perennial ryegrass to adapt to salt stress. The results provided insights into the molecular mechanisms of perennial ryegrass adaptation to salinity and laid a base for genetic improvement of salt tolerance in perennial grass species. [ABSTRACT FROM AUTHOR]

SUMMARY Flavonoids are the major secondary metabolites participating in many biological processes of plants. Although flavonoid biosynthesis has been extensively studied, its regulatory mechanisms during the day and night cycles remain poorly understood. In this study, three proteins, MsMYB206, MsMYB450, and MsHY5, were found to interact with each other, in which MsMYB206 directly transactivated two flavonoid biosynthetic genes, MsFLS and MsF3′H. The expression patterns of MsMYB206, MsMYB450, MsFLS, and MsF3′H were fully consistent at regular intervals across day/night cycles that were higher at night than in the daytime. On the contrary, both gene expression levels and protein contents of MsHY5 increased in the daytime but decreased at night, and the lower expression of MsHY5 at night led to strengthened interaction between MsMYB206 and MsMYB450. The MsMYB206‐overexpression plants were more salt‐tolerant and their flavonoid contents were higher than the WT during the day/night cycles. This study revealed one mechanism interpreting the fluctuating flavonoid contents during day/night cycles regulated by the MsMYB206/MsMYB450/MsHY5‐MsFLS/MsF3′H module that also contributed to salt tolerance in alfalfa. [ABSTRACT FROM AUTHOR]

Melilotus albus, which contains abundant pharmacologically active coumarins, is usually used as a rotation crop and green manure worldwide. Abscisic acid (ABA) is a crucial plant hormone that plays an important role in plant stress responses. There is a paucity of information about the ABA signaling pathway and its regulatory network in M. albus. Here, we performed a comparative physiological and transcriptomic analysis to assess the response of M. albus to exogenous ABA. Physiological analysis revealed that proline (Pro), soluble protein and H2O2 content after ABA treatment 3 h significantly increased by 14.0%, 12.0% and 32.4% compared with 0 h in M. albus. A total of 19,855 differentially expressed genes (DEGs) were identified under ABA treatment, including 13,392 in shoots and 15,471 in roots. We obtained two modules that were significantly correlated with the ABA treatment (the darkorange module was positively correlated at 24 h in the shoot, brown2 module positively correlated at 3 h in the root) by weighted correlation network analysis (WGCNA). KEGG enrichment analysis showed that genes within two modules were primarily enriched in protein synthesis and metabolism, secondary metabolites, purine and pyrimidine metabolism, and phenylalanine, tyrosine and tryptophan biosynthesis. GO enrichment analysis indicated that genes within two modules were primarily enriched in energy substance metabolism. These pathways were mainly associated with abiothic stress, which indicated that exogenous application of ABA activated the stress resistance system of M. albus. The hub gene 4CL1 (4-Coumarate: CoA ligase 1) was translated and expressed in yeast, resulting in enhanced salt and ABA tolerance in the transgenic yeast. Overexpression of Ma4CL1 in M. albus improved the salt resistance of the transgenic plants. Profiling ABA-responsive genes offers valuable insights into the molecular functions of regulatory genes and will facilitate future molecular breeding efforts in M. albus. [ABSTRACT FROM AUTHOR]

Rosa rugosa is a representative aromatic species. Wild roses are known for their strong tolerance to highly salty environments, whereas cultivated varieties of roses exhibit lower salt stress tolerance, limiting their development and industrial expansion. Previous studies have shown that C2H2-type zinc finger proteins play a crucial role in plants' resistance to abiotic stresses. In this study, 102 C2H2-type zinc finger genes (RrC2H2s) were identified in R. rugosa via a comprehensive approach. These genes were categorized into three lineages, and their motif constitutions were grouped into four classes. RrC2H2s were distributed across all seven rose chromosomes, with 15 paralogous gene pairs identified within synteny regions. Additionally, 43 RrC2H2s showed differential expression across various tissues under salt stress, with RrC2H2-8 being the only gene consistently repressed in all tissues. Subcellular localization analysis revealed that the RrC2H2-8 protein was localized in the nucleus. The heterologous expression of RrC2H2-8 in Arabidopsis significantly improved its growth under salt stress compared to the wild-type (WT) plants. Furthermore, the malondialdehyde content in the roots of transgenic Arabidopsis was significantly lower than that in the WT, suggesting that RrC2H2-8 enhanced salt tolerance by reducing cellular damage. This study provides a systematic understanding of the RrC2H2 family and identifies RrC2H2-8 as a regulator of salt tolerance, laying a foundation for future research on the mechanisms of salt stress regulation by RrC2H2. [ABSTRACT FROM AUTHOR]