Salt Stress Response Research Articles

SlbHLH22-Induced Hypertrophy Development Is Related to the Salt Stress Response of the GTgamma Gene in Tomatoes.

Hypertrophy development induced by the overexpression of SlbHLH22 (also called SlUPA-like) was susceptible to Xanthomonas in tomatoes. Transcriptome and metabolome analyses were performed on the hypertrophy leaves of a SlbHLH22-overexpressed line (OE) and wild type (WT) to investigate the molecular mechanism. Metabolome analysis revealed that six key metabolites were over-accumulated in the OE, including Acetylserine/O-Acetyl-L-serine, Glucono-1,5-lactone, Gluconate, 2-Oxoglutarate, and Loganate, implying that the OE plants increased salt or oxidant resistance under normal growth conditions. The RNA-seq analysis showed the changed expressions of downstream genes involved in high-energy consumption, photosynthesis, and transcription regulation in OE lines, and we hypothesized that these biological processes were related to the GTgamma subfamily of trihelix factors. The RT-PCR results showed that the expressions of the GTgamma genes in tomatoes, i.e., SlGT-7 and SlGT-36, were suppressed in the hypertrophy development. The expression of the GTgamma gene was downregulated by salinity, indicating a coordinated role of GTgamma in hypertrophy development and salt stress. Further research showed that both SlGT-7 and SlGT-36 were highly expressed in leaves and could be significantly induced by abscisic acid (ABA). The GTgamma protein had a putative phosphorylation site at S96. These results suggested GTgamma's role in hypertrophy development by increasing the salt resistance.

PagMYB73 enhances salt stress tolerance by regulating reactive oxygen species scavenging and osmotic maintenance in poplar

The MYB transcription factor (TF) family, widely recognized for its involvement in multiple biological processes, holds a significant position among plant TF families due to its substantial size. The R2R3-MYB TF has been extensively studied and known for its pivotal role in regulating the synthesis of anthocyanin, lignin, and secondary wall components in plants. However, there is currently limited information available regarding the function of R2R3-MYB genes in response to salt stress specifically in poplar. Here, we focused on a specific R2R3-MYB gene, PagMYB73, which belongs to the 84K poplar (Populus alba × P. glandulosa) species. We aimed to investigate the role of PagMYB73 in the regulatory mechanisms involved in salt stress response. PagMYB73 showed strong induction in leaves under salt stress conditions. Transgenic poplar plants overexpressing PagMYB73 exhibited enhanced salt tolerance, while suppression of the gene resulted in increased sensitivity to high salt levels. PagMYB73 can regulate the expression of several stress-related genes, including PagGSTU19, PagLEA51, PagSODs, PagPODs, and PagP5CS2. It achieves this by binding to the promoter regions of these genes that orchestrate adaptive responses to salt stress by modulating the osmotic balance and reducing the levels of reactive oxygen species (ROS). Indeed, overexpression of PagGSTU19 and PagLEA51 has been shown to enhance the salt tolerance of poplar. In conclusion, PagMYB73 regulates the expression of stress-related genes to improve ROS scavenging ability and osmotic maintenance, thereby improving the salt tolerance of the transgenic poplar.

In-silico identification and characterization of sucrose transporter genes and their differential expression pattern under salinity stress in Glycine max

Plant sucrose transporters, involved in sugar transport, are key in facilitating sugar flux across the plant cell membranes. However, external stress stimuli significantly impact these sucrose transporters (SWEET/MST/SUT) and, ultimately, the distribution of photosynthates. This has importance as sucrose is a prime energy source, a signaling molecule, and an osmolyte playing a key role in growth and development processes. This study aims to identify and comprehensive in silico characterization and involvement of soybean sucrose transporters GlymaSWEET, GlymaMST, and GlymaSUT in plant development and salt stress responses in an important oilseed crop soybean (Glycine max L.). A genome-wide screening of soybean revealed 13 GlymaSWEET, 6 GlymaMST, and 5 GlymaSUT orthologues as confirmed from the eggNOG database. Probable sites of these proteins were found to be the membranes of cells and organelles, as suggested by their sub-cellular localization. The cis-regulatory elements of these transporters’ promoters indicated their involvement in environmental stress responses. MicroRNA interactions with these transporters were also studied, besides 3-D protein structure prediction using in silico approaches. To gain an insight into the functional divergence of GlymaSWEET, GlymaMST, and GlymaSUT transporters, qRT-PCR-based gene expression analysis was done both in control and salt-treated root and leaf tissues of two contrasting Indian soybean varieties MAUS-47 (salt-tolerant) and Gujosoya-2 (salt-sensitive). Differential gene expression was observed with varying degrees amongst the varieties and the treatments. Overall, we can conclude that the identified GlymaSWEET, GlymaMST, and GlymaSUT have the potential to be explored as candidate genes for engineering salinity stress tolerance in soybean and other plants.

Calcium regulation of the Arabidopsis Na+/K+ transporter HKT1;1 improves seed germination under salt stress.

Calcium is known to improve seed-germination rates under salt stress. We investigated the involvement of calcium ions (Ca2+) in regulating HIGH-AFFINITY K+ TRANSPORTER 1 (HKT1; 1), which encodes a Na+/K+ transporter, and its post-translational regulator TYPE 2C PROTEIN PHOSPHATASE 49 (PP2C49), in germinating Arabidopsis (Arabidopsis thaliana) seedlings. Germination rates of hkt1 mutant seeds under salt stress remained unchanged by CaCl2 treatment in wild-type Arabidopsis, whereas pp2c49 mutant seeds displayed improved salt-stress tolerance in the absence of CaCl2 supplementation. Analysis of HKT1;1 and PP2C49 promoter activity revealed that CaCl2 treatment results in radicle-focused expression of HKT1;1 and reduction of the native radicle-exclusive expression of PP2C49. Ion-content analysis indicated that CaCl2 treatment improves K+ retention in germinating wild-type seedlings under salt stress, but not in hkt1 seedlings. Transgenic seedlings designed to exclusively express HKT1;1 in the radicle during germination displayed higher germination rates under salt stress than the wild type in the absence of CaCl2 treatment. Transcriptome analysis of germinating seedlings treated with CaCl2, NaCl, or both revealed 118 upregulated and 94 downregulated genes as responsive to the combined treatment. Bioinformatics analysis of the upstream sequences of CaCl2-NaCl-treatment-responsive upregulated genes revealed the abscisic acid response element CACGTGTC, a potential CaM-binding transcription activator-binding motif, as most prominent. Our findings suggest a key role for Ca2+ in mediating salt-stress responses during germination by regulating genes that function to maintain Na+ and K+ homeostasis, which is vital for seed germination under salt stress.

Corrigendum to: Salt tolerance in Brassicaceae crops: physiological responses and molecular mechanisms.

Soil salinisation is a growing threat to global agriculture, reducing crop yields. Brassicaceae crops are vital vegetables and cash crops. Salt stress significantly affects the growth and development of Brassicaceae crops. A better understanding of the molecular and physiological mechanisms of salt tolerance is of theoretical and practical importance to improve Brassicaceae crop's salt tolerance and crop quality. Combined with previous research results, we discuss recent advances in research on salt stress response and salt tolerance in Brassicaceae crops. We summarised recent research progress on the physiological and molecular mechanisms of ionic homeostasis, antioxidant regulation, hormonal regulation and accumulation of osmotic-adjustment substances. We also discussed the molecular mechanism of Brassicaceae crop salt tolerant varieties from the perspective of differentially expressed genes, differentially expressed proteins and metabolites through transcriptome, proteome and metabonomic analysis methods. This paper summarises the molecular mechanisms in the perspective of differentially expressed genes, differentially expressed proteins, and metabolites through transcriptomic, proteome and metabolomics analysis. The review provides abundant data for accelerating the breeding of salt-tolerant Brassicaceae and laid a foundation for understanding the mechanism of salt tolerance of Brassicaceae crops and breeding salt-tolerance varieties.

Dynamic physiological and transcriptomic changes reveal memory effects of salt stress in maize

BackgroundPre-exposing plants to abiotic stresses can induce stress memory, which is crucial for adapting to subsequent stress exposure. Although numerous genes involved in salt stress response have been identified, the understanding of memory responses to salt stress remains limited.ResultsIn this study, we conducted physiological and transcriptional assays on maize plants subjected to recurrent salt stress to characterize salt stress memory. During the second exposure to salt stress, the plants exhibited enhanced salt resistance, as evidenced by increased proline content and higher POD and SOD activity, along with decreased MDA content, indicative of physiological memory behavior. Transcriptional analysis revealed fewer differentially expressed genes and variations in response processes during the second exposure compared to the first, indicative of transcriptional memory behavior. A total of 2,213 salt stress memory genes (SMGs) were identified and categorized into four response patterns. The most prominent group of SMGs consisted of genes with elevated expression during the first exposure to salt stress but reduced expression after recurrent exposure to salt stress, or vice versa ([+ / −] or [− / +]), indicating that a revised response is a crucial process in plant stress memory. Furthermore, nine transcription factors (TFs) (WRKY40, WRKY46, WRKY53, WRKY18, WRKY33, WRKY70, MYB15, KNAT7, and WRKY54) were identified as crucial factors related to salt stress memory. These TFs regulate over 53% of SMGs, underscoring their potential significance in salt stress memory.ConclusionsOur study demonstrates that maize can develop salt stress memory, and the genes identified here will aid in the genetic improvement of maize and other crops.

SmWRKY11 acts as a positive regulator in eggplant response to salt stress

Salt stress is one of the most threatening abiotic stresses to plants, which can seriously affect plant growth, development, reproduction, and yield. However, the mechanisms of plant against salt stress largely remain unclear. Herein, SmWRKY11, an assumed WRKY transcription factor, was functionally characterized in eggplant against salt stress. SmWRKY11 was significantly up-regulated by salt, dehydration stress, and ABA treatment. SmWRKY11 located in the nucleus, and the Plant_zn_clust conserved domain exhibited transcriptional activation activity. Silencing of SmWRKY11 enhanced the susceptibility of eggplant to salt stress, accompanied by significantly down-regulation of transcript expression levels of salt stress defense-related genes SmNCED1, SmGSTU10, and positive regulator of salt stress response SmERF1 as well as increase of hydrogen peroxide (H2O2) content and decrease of the enzyme activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). In addition, silencing of SmERF1 also could significantly down-regulate SmWRKY11 expression in eggplant response to salt stress. By luciferase reporter assay and chromatin immunoprecipitation PCR assay, SmERF1 expression was found to be indirectly activated by SmWRKY11. These data indicate that SmWRKY11 acts as a positive regulator by forming positive feedback loop with SmERF1 via an indirect regulatory manner in eggplant response to salt stress.

MdNup62 involved in salt and osmotic stress tolerance in apple

Abiotic stress of plants has serious consequences on the development of the apple industry. Nuclear pore complexes (NPCs) control nucleoplasmic transport and play an important role in the regulation of plant abiotic stress response. However, the effects of NPCs on apple salt and osmotic stress responses have not been reported yet. In this study, we analyzed the expression and function of NUCLEOPORIN 62 (MdNup62), a component of apple NPC. MdNup62 expression was significantly increased by salt and mannitol (simulated osmotic stress) treatment. The MdNup62-overexpressing (OE) Arabidopsis and tomato lines exhibited significantly reduced salt stress tolerance, and MdNup62-OE Arabidopsis lines exhibited reduced osmotic stress tolerance. We further studied the function of HEAT SHOCK FACTOR A1d (MdHSFA1d), the interacting protein of MdNup62, in salt and osmotic stress tolerance. In contrast to MdNup62, MdHSFA1d-OE Arabidopsis lines showed significantly enhanced tolerance to salt and osmotic stress. Our findings suggest a possible interaction of MdNup62 with MdHSFA1d in the mediation of nuclear and cytoplasmic transport and the regulation of apple salt and osmotic stress tolerance. These results contribute to the understanding of the salt and osmotic stress response mechanism in apple.

Novel underlying regulatory mechanism of the MsDAD2-mediated salt stress response in alfalfa

Alfalfa (Medicago sativa L.), a crucial and widely grown forage legume, faces yield and quality challenges due to salinity stress. The defender against apoptotic death (DAD) gene, recognized initially as an apoptosis suppressor in mammals, plays a pivotal role in catalyzing N-glycosylation, acting as a positive regulator for protein folding and endoplasmic reticulum (ER) export. Here, we found that the MsDAD2 gene was specially induced in the salt-tolerant alfalfa cultivar (DL) under salinity stress, but not in the salt-sensitive cultivar (SD). Overexpression of MsDAD2 enhanced the salinity resistance of transgenic alfalfa by promoting NAD(P)H-quinone oxidoreductase (NQO1) and cytochrome b6f complex subunit (Cyt b6/f) expression, thereby mitigating reactive oxygen species (ROS) production. ChIP-qPCR analysis suggested that the differential expression of MsDAD2 in DL and SD under salinity stress may be linked to dynamic histone modifications in its promoter. Therefore, our findings elucidate a novel regulatory mechanism of MsDAD2 in alfalfa's response to salinity stress, underscoring its significance as a target for alfalfa breeding to enhance salt tolerance.

Deciphering the regulatory networks involved in mild and severe salt stress responses in the roots of wild grapevine Vitis vinifera spp. sylvestris.

Transcriptional regulatory networks are pivotal components of plant's response to salt stress. However, plant adaptation strategies varied as a function of stress intensity, which is mainly modulated by climate change. Here, we determined the gene regulatory networks based on transcription factor (TF) TF_gene co-expression, using two transcriptomic data sets generated from the salt-tolerant "Tebaba" roots either treated with 50mM NaCl (mild stress) or 150mM NaCl (severe stress). The analysis of these regulatory networks identified specific TFs as key regulatory hubs as evidenced by their multiple interactions with different target genes related to stress response. Indeed, under mild stress, NAC and bHLH TFs were identified as central hubs regulating nitrogen storage process. Moreover, HSF TFs were revealed as a regulatory hub regulating various aspects of cellular metabolism including flavonoid biosynthesis, protein processing, phenylpropanoid metabolism, galactose metabolism, and heat shock proteins. These processes are essentially linked to short-term acclimatization under mild salt stress. This was further consolidated by the protein-protein interaction (PPI) network analysis showing structural and plant growth adjustment. Conversely, under severe salt stress, dramatic metabolic changes were observed leading to novel TF members including MYB family as regulatory hubs controlling isoflavonoid biosynthesis, oxidative stress response, abscisic acid signaling pathway, and proteolysis. The PPI network analysis also revealed deeper stress defense changes aiming to restore plant metabolic homeostasis when facing severe salt stress. Overall, both the gene co-expression and PPI network provided valuable insights on key transcription factor hubs that can be employed as candidates for future genetic crop engineering programs.

PacBio Full-Length Transcriptome Sequencing Reveals the Mechanism of Salt Stress Response in Sonneratia apetala.

Sonneratia apetala is an essential mangrove wetland restoration tree species. Studying its molecular mechanism for salt tolerance could lay a foundation for further cultivating excellent resistant germplasm. This study used a combination of PacBio isoform sequencing (Iso-seq) and BGISEQ RNA sequencing (RNA-seq) to analyze the molecular mechanism to salt stress response of one-year-old S. apetala leaves. The growth and physiological analysis showed that physiological indexes such as growth rate, net photosynthetic rate and antioxidant enzyme activity all exhibit significant changes under salt stress. From Iso-seq, a total of 295,501 full-length transcripts, with an average length of 1418 bp, were obtained. RNA-seq produced 4712 differentially expressed genes (DEGs) as compared to a control group. Of these, 930 were identified to be co-expressed during the STEM time sequence analysis. Further, 715 and 444 co-expressed DEGs were annotated by GO and KEGG analyses, respectively. Moreover, 318 of the co-expressed DEGs were annotated as essential genes that were implicated in salt stress response of S. apetala, which were involved in transcription factors, signal transduction, hormone response, ROS homeostasis, osmotic balance, cell wall synthesis or modification. These results provide candidate targets for further characterization and offer insights into the salt-tolerant mechanism of S. apetala.

Jacalin-related lectin 45 (OsJRL45) isolated from ‘sea rice 86’ enhances rice salt tolerance at the seedling and reproductive stages

BackgroundRice (Oryza sativa L.) is one of the most widely cultivated grain crops in the world that meets the caloric needs of more than half the world’s population. Salt stress seriously affects rice production and threatens food security. Therefore, mining salt tolerance genes in salt-tolerant germplasm and elucidating their molecular mechanisms in rice are necessary for the breeding of salt tolerant cultivars.ResultsIn this study, a salt stress-responsive jacalin-related lectin (JRL) family gene, OsJRL45, was identified in the salt-tolerant rice variety ‘sea rice 86’ (SR86). OsJRL45 showed high expression level in leaves, and the corresponding protein mainly localized to the endoplasmic reticulum. The knockout mutant and overexpression lines of OsJRL45 revealed that OsJRL45 positively regulates the salt tolerance of rice plants at all growth stages. Compared with the wild type (WT), the OsJRL45 overexpression lines showed greater salt tolerance at the reproductive stage, and significantly higher seed setting rate and 1,000-grain weight. Moreover, OsJRL45 expression significantly improved the salt-resistant ability and yield of a salt-sensitive indica cultivar, L6-23. Furthermore, OsJRL45 enhanced the antioxidant capacity of rice plants and facilitated the maintenance of Na+-K+ homeostasis under salt stress conditions. Five proteins associated with OsJRL45 were screened by transcriptome and interaction network analysis, of which one, the transmembrane transporter Os10g0210500 affects the salt tolerance of rice by regulating ion transport-, salt stress-, and hormone-responsive proteins.ConclusionsThe OsJRL45 gene isolated from SR86 positively regulated the salt tolerance of rice plants at all growth stages, and significantly increased the yield of salt-sensitive rice cultivar under NaCl treatment. OsJRL45 increased the activity of antioxidant enzyme of rice and regulated Na+/K+ dynamic equilibrium under salinity conditions. Our data suggest that OsJRL45 may improve the salt tolerance of rice by mediating the expression of ion transport-, salt stress response-, and hormone response-related genes.

Expression of Cowpea VuWRKY21 and VuWRKY87 Genes in Arabidopsis thaliana Confers Plant Tolerance to Salt Stress

WRKY transcription factors play a pivotal role in regulating stress signaling pathways, including those associated with salt stress response. The present work characterized the effects of two WRKY genes from Vigna unguiculata, namely VuWRKY21 and VuWRKY87, on enhancing plant salinity tolerance. Under salt stress conditions, Arabidopsis lines expressing VuWRKY21 or VuWRKY87 showed elevated expression of genes participating in saline stress response pathways and reduced oxidative stress induced by reactive oxygen species (ROS). Among the salt-responsive genes in Arabidopsis, AtP5CS1, AtNHX1, AtRD29A, AtSOS3, AtSOS2, and AtSOS1 exhibited modulated expression levels after stress imposition. Furthermore, compared to wild-type plants, at most evaluated times, transgenic lines, on average, presented lower H2O2 content while displaying higher content of SOD (EC: 1.15.1.1) and CAT (EC: 1.11.1.6) at early stages of salt stress. These findings suggest that the expression of both VuWRKY genes in Arabidopsis, particularly VuWRKY21, activated genes involved in salinity tolerance.

Metabolomics analysis reveals the effect of removing cotyledons on salt tolerance in castor plant roots during early seedling establishment

Castor is an important oil crop with moderate salt tolerance that is grown worldwide. The early seedling stage is the most vulnerable phase during a plant’s lifecycle in a saline environment. Cotyledons play an important role in seedling establishment as the storage and first photosynthetic organ, and in the resistance of the seedling to salt stress. However, how cotyledons affect the metabolic response of castor roots in saline environments is unclear. Here, liquid chromatography-mass spectrometry analytical methods were used to examine the effects of removing cotyledons (no cotyledons removed, NR; one cotyledon removed, OR; both cotyledons removed, TR) on the metabolite changes in the roots under salt stress. The results showed that removing cotyledons inhibited the growth of TR roots much greater than NR or OR roots. Metabolomics analysis showed that the roots of TR seedlings had fewer metabolites involved in the salt stress response than NR seedlings. Moreover, the KEGG pathway enrichment analysis demonstrated that salt-induced metabolites were associated with major biological pathways related to tropane, piperidine, and pyridine alkaloid biosynthesis; amino acid biosynthesis; phenylpropanoid biosynthesis; amino sugar and nucleotide sugar metabolism, as well as arginine and proline metabolism. However, the contents of these metabolites decreased or did not change significantly in the TR roots compared to the NR roots under salt stress. Additionally, the contents of caffeyl alcohol, scopoletin, and syringin in the phenylpropanoid biosynthetic pathway increased significantly in the roots of TR seedlings under salt stress compared to the control treatment. Therefore, we concluded that castor plants with cotyledons enhanced particular metabolic pathways in the roots that protected cell membrane structure, maintained cell osmotic potential, resisted reactive oxygen species and provided energy under salt stress. In addition, the roots of castor plants without cotyledons may be resistant to salt stress by enhancing phenylpropanoid biosynthesis to maintain cell differentiation and enhance root lignification. Taken together, these findings provide new insight into the physiological functions of cotyledons in the aboveground-belowground interactions of castor plants under salt stress.

Molecular insights into the salt stress response of Pearl millet (Pennisetum glaucum): Pathways, differentially expressed genes and transcription factors

AbstractIntroductionPearl millet (Pennisetum glaucum) plays a crucial role as a cereal crop in arid and semi‐arid regions, where it confronts the formidable challenge of salt stress.Materials and MethodsTo unravel the underlying molecular mechanisms that underpin its salt stress resilience, we subjected 14‐day‐old seedlings to three distinct groups: Control, 75 mM NaCl and 150 mM NaCl. These pots received daily irrigation with their respective treatment solutions for a duration of 7 days. Following this week‐long treatment, we measured plant chlorophyll content, as well as the fresh and dry weights of shoots and roots. It became evident that the saline treatment, particularly in the 150 mM NaCl group, had a more pronounced impact on both weight and chlorophyll content in comparison to the control group, surpassing the effects observed in the 75 mM NaCl group. Subsequently, we conducted RNA sequence analysis on the leaves of Pearl millet from both the control and 150 mM NaCl‐treated groups.ResultsThe results revealed that 27.6% of Pennisetum glaucum genes exhibited differential expression, with 3246 genes being upregulated and 7408 genes downregulated when compared to the control group. Principal component analysis underscored distinct variations in gene expression patterns between the control and salt‐stressed groups. Pathway analysis sheds light on the upregulated differentially expressed genes (DEGs), highlighting their involvement in crucial pathways such as phytyl‐PP biosynthesis, lysine degradation, glutamate biosynthesis, nitrate assimilation and DLO biosynthesis. Conversely, the downregulated DEGs were associated with pathways like coumarins biosynthesis, pinobanksin biosynthesis, UDP‐ d‐glucuronate biosynthesis and cholesterol biosynthesis, among others. Furthermore, our transcription factor analysis unveiled specific families associated with the salt stress response, including bHLH, ERF, NAC, WRKY, bZIP, MYB and HD‐ZIP.ConclusionsThese findings represent a significant advancement in our comprehension of Pearl millet's capacity to withstand salt stress and provide potential targets for the development of salt‐resistant crops, contributing to the advancement of sustainable agriculture in regions affected by salinity.

Identification and functional characterization of a novel TRPA1 gene from sea cucumber Apostichopus japonicus and interaction with miR-2013 in response to salt stress.

Salinity is important abiotic factor influencing sea cucumber aquaculture. This study aimed to identify and functional study of a novel transient receptor potential cation channel subfamily A member 1 (TRPA1) involved in salinity stress through interaction with miR-2013 in the sea cucumber. The full-length cDNA sequence was 1369bp in length and encoded 138 amino acids. The TRPA1 homolog protein was a hydrophilic protein without a signal peptide and was predicted to a spatial structure of seven helices and eight random coils and two major ANK functional domains. Bioinformatic analysis and luciferase reporter assays confirmed TRPA1 as a target gene of miR-2013. Quantitative PCR revealed that miR-2013 was induced upregulation after salinity stress, while TRPA1 showed upregulated expression with maximum expression at 24h. The expression of miR-2013 and TRPA1 was negatively regulated. Transfection experiments were conducted to validate the role of miR-2013 and TRPA1 in salinity response. The results showed that miR-2013 was upregulated and TRPA1 was downregulated after transfection with miR-2013 mimics, while miR-2013 was downregulated and TRPA1 was upregulated after transfection with miR-2013 inhibitor. Transfection with si-TRPA1 homolog resulted in upregulation of miR-2013 and downregulation of TRPA1 homolog. These findings suggest that miR-2013 can regulate the expression of TRPA1 under salt stress, and highlight the importance of miR-2013 and TRPA1 in salt stress response. miR-2013 mimics improved the survival rate, while miR-2013 inhibitor and si-TRPA1 reduced it. These findings suggest that miR-2013 and TRPA1 play important roles in sea cucumbers adaptation to salinity changes.

Genome-wide identification and characterization of filamentation temperature-sensitive H (FtsH) genes and expression analysis in response to multiple stresses in Medicago truncatula.

Filamentation temperature-sensitive H (FtsH) is an AAA+ ATP-dependent protease that plays a vital role in plant environmental adaption and tolerance. However, little is known about the function of the FtsH gene family in the most important legume model plant, Medicago truncatula. To identify and investigate the potential stress adaptation roles of FtsH gene family in M. truncatula, we conducted a series of genome-wide characterization and expression analyses. Totally, twenty MtFtsH genes were identified, which were unevenly distributed across eight chromosomes and classified into six evolution groups based on their phylogenetic relationships, with each group containing similar structures and motifs. Furthermore, MtFtsH genes exhibited a high degree of collinearity and homology with leguminous plants such as alfalfa and soybean. Multiple cis-elements in the upstream region of MtFtsH genes were also identified that responded to light, abiotic stress, and phytohormones. Public RNA-seq data indicated that MtFtsH genes were induced under both salt and drought stresses, and our transcript expression analysis showed that MtFtsH genes of MtFtsH1, MtFtsH2, MtFtsH4, MtFtsH9, and MtFtsH10 were up-regulated after ABA, H2O2, PEG, and NaCl treatments. These results suggest that MtFtsH genes may play a critical role in drought and high salt stress responses and the adaption processes of plants. This study provides a systematic analysis of FtsH gene family in M. truncatula, serving as a valuable molecular theoretical basis for future functional investigations. Our findings also extend the pool of potential candidate genes for the genetic improvement of abiotic stress tolerance in legume crops.

Transcriptional landscape of cotton roots in response to salt stress at single-cell resolution

Increasing soil salinization has led to severe reductions in plant yield and quality, and investigating the molecular mechanism of salt stress response is therefore an urgent priority. In this study, we systematically analyzed the response of cotton roots to salt stress using single-cell transcriptomics technology; 56 281 high-quality cells were obtained from 5-day-old lateral root tips of Gossypium arboreum under natural growth conditions and different salt treatments. Ten cell types with an array of novel marker genes were identified and confirmed by in situ RNA hybridization, and pseudotime analysis of some specific cell types revealed their potential differentiation trajectories. Prominent changes in cell numbers under salt stress were observed for outer epidermal and inner endodermal cells, which were significantly enriched in response to stress, amide biosynthetic process, glutathione metabolism, and glycolysis/gluconeogenesis. Analysis of differentially expressed genes identified in multiple comparisons revealed other functional aggregations concentrated on plant-type primary cell wall biogenesis, defense response, phenylpropanoid biosynthesis, and metabolic pathways. Some candidate differentially expressed genes encoding transcription factors or associated with plant hormones also responsive to salt stress were identified, and the function of Ga03G2153, annotated as auxin-responsive GH3.6, was confirmed by virus-induced gene silencing. The GaGH3.6-silenced plants showed a severe stress-susceptible phenotype, and physiological and biochemical measurements indicated that they suffered more significant oxidative damage. These results suggest that GaGH3.6 might participate in cotton salt tolerance by regulating redox processes. We thus construct a transcriptional atlas of salt-stressed cotton roots at single-cell resolution, enabling us to explore cellular heterogeneity and differentiation trajectories and providing valuable insights into the molecular mechanisms that underlie plant stress tolerance.

The Arabidopsis ubiquitin ligases ATL31 and ATL6 regulate plant response to salt stress in an ABA-independent manner

E3 ubiquitin ligases play critical roles in regulating plant response to salt stress. Arabidopsis Tóxicos En Levadura (ATL) is a subfamily of RING-type E3 ubiquitin ligases widely conserved in plant species. ATL genes have been shown to be involved in regulating plant response to biotic or abiotic stresses. We previously found that a pair of ATL genes, ATL31 and ATL6 positively regulated plant innate immunity. However, whether ATL31/6 are also involved in salt stress response remains to be investigated. Here, we demonstrate that ATL31/6 are induced by salt stress. The atl31 atl6 double mutant exhibits increased salt tolerance compared to the wild-type plants, while transgenic plants overexpressing ATL31 are more salt-sensitive. Notably, ATL31 and ATL6 do not participate in the abscisic acid (ABA) response. Furthermore, NaCl treatment induces the proteasomal degradation of ATL31 proteins. Together, we demonstrate that ATL31/6 positively regulate plant tolerance to salt stress, which is independent of ABA, and our work reveals that ATL31/6 are involved in regulating plant response to both biotic and abiotic stress.

Identification and characterization of salt stress-responsive NHX gene family in chickpea

Chickpea (Cicer arietinum L.) is an important legume crop, primarily grown in the arid and semi-arid regions. It is a valuable protein source and rich in minerals, especially calcium and phosphorus. Salinity stress adversely affects chickpea germination, vegetative growth, and reproductive activities. The Na+/H+ exchanger (NHX), a gene family of membrane transporters, is well recognized for inducing salt tolerance in plants. The NHXs assist in maintaining ion and pH homeostasis in cells by exchanging K+ or Na+ for H+. This study was designed to identify and characterize the NHX genes for salt stress responsiveness in chickpea. Eight NHX genes were identified in chickpea. The phylogenetic analysis represented the evolutionary relationship of Cicer arietinum NHXs (CarNHXs) with Glycine max, Medicago truncatula, Lotus japonicus, Phaseolus vulgaris, Lens culinaris, Vigna unguiculata, and Oryza sativa. The in-silico gene expression analysis indicated high expression of CarNHX3 (Ca_19073) and CarNHX7 (Ca_02050) under salt stress. The qRT-PCR further validated that the expression of CarNHX3 and CarNHX7 increased when plants were exposed to salt stress. This study provides a way forward to plan functional research to exploit CarNHX genes to enhance salt-tolerance in chickpea.