Salt-sensitive Phenotype Research Articles

Kifunensine-sensitive ADP-ribosylation factor A1EG69R mutant revealed coordination of protein glycosylation and vesicle transport pathways.

Complex N-glycans are asparagine (N)-linked branched sugar chains attached to secretory proteins in eukaryotes. They are produced by modification of N-linked oligosaccharide structures in the endoplasmic reticulum (ER) and Golgi apparatus. Complex N-glycans formed in the Golgi apparatus are often assigned specific roles unique to the host organism, with their roles in plants remaining largely unknown. Using inhibitor (kifunensine, KIF)-hypersensitivity as read-out, we identified Arabidopsis mutants that require complex N-glycan modification. Among over 100 KIF-sensitive mutants, one showing abnormal secretory organelles and a salt-sensitive phenotype contained a point mutation leading to amino-acid replacement (G69R) in ARFA1E, a small Arf1-GTPase family protein presumably involved in vesicular transport. In-vitro assays showed that the G69R exchange interferes with protein activation. In vivo, ARFA1EG69R caused dominant-negative effects, altering the morphology of the ER, Golgi apparatus, and trans-Golgi network (TGN). Post-Golgi transports (endocytosis/endocytic recycling) of essential glycoprotein KORRIGAN1, one of KIF-sensitivity targets, is slowed down constitutively as well as under salt stress in ARFA1EG69R mutant. Because regulated cycling of plasma membrane proteins is required for stress tolerance of the host plants, ARFA1EG69R mutant established a link between KIF-targeted luminal glycoprotein functions/dynamics and cytosolic regulators of vesicle transport in endosome-/cell wall-associated tolerance mechanisms.

CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 regulates salt tolerance through CATALASE 2 in Arabidopsis.

Soil salinization threatens global crop production. Here, we report that a receptor-like cytoplasmic kinase (RLCK), CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 (CRCK3), plays an essential role in plant salt tolerance via CATALASE 2 (CAT2), a hydrogen peroxide (H2O2)-scavenging enzyme in Arabidopsis (Arabidopsis thaliana). CRCK3 was induced by salt stress, and its knockout mutant displayed a salt-sensitive phenotype compared to wild-type (WT) plants. CRCK3 was activated by salt stress in a calcium-dependent manner, and its kinase activity was required for plant salt tolerance. CRCK3 physically interacted with CAT2, and CRCK3-mediated salt tolerance depended on CAT2. Salt treatment significantly induced CAT2 phosphorylation via the action of CRCK3, and this phosphorylation was required for CAT2-mediated H2O2 scavenging to reduce ROS content and oxidative damage in plants under saline conditions. CRCK3 phosphorylated CAT2 at the Thr209 residue, resulting in elevated catalase activity to reduce reactive oxygen species (ROS) accumulation under saline conditions. Therefore, the CRCK3-CAT2 module mediates plant salt tolerance by maintaining redox homeostasis. This study expands our knowledge of how plants respond to salt stress.

Heterologous expression of the durum wheat TdHKT1;4-1 partially complements the mutant athkt1 in Arabidopsis thaliana under severe salt stress.

High-affinity K+ (HKT) transporters which mediate Na+-specific transport or Na+-K+ co-transport play a key role in plant salt tolerance. In our previous functional study in Xenopus oocytes, we demonstrated that the durum wheat TdHKT1;4-1 acts as a Na+-selective transporter. Here, we investigated the function of TdHKT1;4-1 and its contribution in salt stress tolerance in the Arabidopsis athkt1 mutant background. Our results revealed that TdHKT1;4-1 partially complements the salt sensitivity phenotype of the athkt1 transgenic lines. Comparative physiological analyses and oxidative stress status under moderate salt stress (50mM NaCl) showed that both transgenic lines SH3 and SH5 restored the salt stress tolerance comparable to the level observed in Wt plants. Whereas, under severe salt stress treatment (100mM NaCl), the athkt1 transgenic lines exhibited an intermediate salt stress tolerance between Wt and athkt1 mutant. Moreover, TdHKT1;4-1 was highly expressed in leaves under moderate and severe salt stress, while in roots, it was largely expressed only under severe salt stress. In addition, antioxidant enzymes such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were significantly expressed in SH3 and SH5 lines compared to athkt1 and Wt under moderate stress. Therefore, TdHKT1;4-1 seems to differ from its Arabidopsis homologous counterpart, as it contributes to salt stress tolerance up to a specific threshold, above which the TdHKT1;4-1 expression may lead to higher root Na+ influx, hence increasing its toxicity during salt stress.

ABCG Transporters in the Adaptation of Rice to Salt Stresses

The ATP-binding cassette (ABC) proteins are a diverse family of transmembrane transporter proteins widely identified in various organisms. The ABCG transporters belong to the G subfamily of the ABC transporter family. Rarely research on ABCG transporters involved in salt tolerance of rice was found. In this study, the evolutionary relationships, conserved motifs, intra- and inter-species homologous genes, and cis-acting elements of ABCG subfamily members were analyzed, and the expression changes of these genes under salt stress at 0 h, 3 h, and 24 h were detected. Based on these results, the candidate gene OsABCG7, which is induced by salt stress, was selected for further studies. Yeast experiments confirmed that the OsABCG7 gene might be involved in the regulation of salt tolerance. The abcg7 mutant showed a higher degree of leaf wilting and a lower survival rate, exhibiting a salt-sensitive phenotype. Systematic analysis of this family in rice helps design effective functional analysis strategies and provides data support for understanding the role of ABCG transporters under salt stress.

Genome‑wide analysis of cotton SCAMP genes and functional characterization of GhSCAMP2 and GhSCAMP4 in salt tolerance

BackgroundSecretory carrier membrane proteins (SCAMPs) form a family of integral membrane proteins and play a crucial role in mediating exocytosis in both animals and plants. While SCAMP genes have been studied in several plant species, their functions in cotton, particularly in response to abiotic stress, have not yet been reported.ResultsIn this study, a total of 53 SCAMP genes were identified in G. arboreum, G. raimondii, G. hirsutum, and G. barbadense. These genes were classified into five groups based on a phylogenetic analysis with SCAMPs from Arabidopsis thaliana. The main factor driving the expansion of the SCAMP gene family in G. hirsutum is tandem and segmental duplication events. Using MEME, in addition to the conserved SCAMP domain, we identified 3–13 other domains in each GhSCAMP. The cis-element analysis suggested that GhSCAMPs were widely involved in cotton growth and development, and responses to abiotic stresses. RNA sequencing (RNA-Seq) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results showed that most GhSCAMPs were expressed highly in many tissues and had differential expression responses to drought, cold, and heat stresses. Knock-down of GhSCAMP2 and GhSCAMP4 by virus-induced gene silencing (VIGS) lead to a salt-sensitive phenotype and had a lower content of CAT, POD, and SOD.ConclusionsThis study identified SCAMP genes in four cotton species, enhancing our understanding of the potential biological functions of SCAMPs. Additionally, we demonstrated that GhSCAMP2 and GhSCAMP4 positively regulate cotton tolerance to salt stress.

Overexpression of GhGSTF9 Enhances Salt Stress Tolerance in Transgenic Arabidopsis.

Soil salinization is a major abiotic stress factor that negatively impacts plant growth, development, and crop yield, severely limiting agricultural production and economic development. Cotton, a key cash crop, is commonly cultivated as a pioneer crop in regions with saline-alkali soil due to its relatively strong tolerance to salt. This characteristic renders it a valuable subject for investigating the molecular mechanisms underlying plant salt tolerance and for identifying genes that confer salt tolerance. In this study, focus was placed on examining a salt-tolerant variety, E991, and a salt-sensitive variety, ZM24. A combined analysis of transcriptomic data from these cotton varieties led to the identification of potential salt stress-responsive genes within the glutathione S-transferase (GST) family. These versatile enzyme proteins, prevalent in animals, plants, and microorganisms, were demonstrated to be involved in various abiotic stress responses. Our findings indicate that suppressing GhGSTF9 in cotton led to a notably salt-sensitive phenotype, whereas heterologous overexpression in Arabidopsis plants decreases the accumulation of reactive oxygen species under salt stress, thereby enhancing salt stress tolerance. This suggests that GhGSTF9 serves as a positive regulator in cotton's response to salt stress. These results offer new target genes for developing salt-tolerant cotton varieties.

#1463 Assessment of salt-sensitive hypertension in a novel Lanosterol Synthase knock-in mouse model

Abstract Background and Aims The diversity in blood pressure (BP) response to various salt intakes, known as Salt Sensitivity (SS), exhibits significant differences among individuals within the hypertensive subjects relative to the general population. Hypertension (HT) and SS are correlated to elevated levels of plasma Endogenous Ouabain (EO). We aimed at delineating the role of the missense variation rs2254524 (Val642Leu; C>A) within the Lanosterol Synthase gene (LSS), encoding for an enzyme involved in steroid biosynthesis. Individuals with the AA LSS variant, adherent to a low-salt diet, had a more significant BP reduction compared to those with CC genotype. Method Utilising CRISPR-Cas9, we established a knock-in mouse model carrying the analogous LssV643L/V643L. Male mice were subjected to a normal-salt diet (0.5% NaCl), high-salt diet (4% NaCl), or low-salt diet (<0.03% Na) and BP was monitored every two days using a tail-cuff system for 10 days. Blood and urine were collected separately in metabolic cages. Results Homozygous mice for Lss mutation demonstrated normal viability and healthy phenotype, undistinguishable from the WT. At baseline, the Lss AA mice were affected by a significant augmentation in kidney weight at 3 and 12 months of age, relative to WT. The Lss V643L does not influence EO levels or systolic BP (SBP), specifically at 3 and 12 months, but affects the SBP response to dietary salt. AA mice showed a high SBP in a high-salt diet against control diet at the same time intervals. Moreover, the Lss variant impacted the pressure-natriuresis relationship, with the mutated AA strain showing a less steep curve both in control diet versus the high-salt diet and in control diet versus the low-salt diet, displaying the SS phenotype of the AA mice. The 12-month-old mice in high-salt diet displayed cardiac hypertrophy with the AA genotype exhibiting an elevated prevalence of cardiac fibrosis. The level of Lss mRNA decreased in the adrenal glands in response to a high-salt diet. RNASeq analysis identified distinct patterns in several Slc genes, Cbr2 and Arhgap26 within the kidneys of these mice, in control or high-salt dietary conditions. Conclusion The established LssV643L/V643L mouse model effectively mirrors the SS-HT phenotype. Our findings highlight the significance of the Lss in modulating BP in response to salt stimuli suggesting a potential organ damage pathway requiring further exploration in older mice.

Transcriptomic profiling reveals salt-responsive long non-coding RNAs and their putative target genes for improving salt tolerance in upland cotton (Gossypium hirsutum)

Salt stress continues to exert notable impacts on the growth and development of cotton plants. In various biological processes of plants and in response to abiotic stress, long noncoding RNAs (lncRNAs) play a crucial regulatory role. In this study, we conducted transcriptome sequencing of cotton plants grown under salt stress and normal water conditions. A total of 519 lncRNAs and 75,376 messenger RNAs (mRNAs) were identified. Compared with mRNAs, lncRNAs have shorter transcript lengths and open reading frames, fewer exons, and lower expression levels. By comparing and analyzing the differentially expressed lncRNAs (DELs) and differentially expressed coding genes (DEGs) after salt treatment, we identified a total of 60 DELs and 217 DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that these target genes are enriched primarily in intracellular organelles and participate in metabolic regulation pathways. Ultimately, lncRNA XLOC_043671, along with its target gene Gohir.D02G125200, and the lncRNA XLOC_034831, along with its target gene Gohir.A12G114800 was identified as a participant in salt tolerance regulation in cotton. RNA-seq and RTqPCR revealed that both these lncRNAs and their target genes exhibited significantly enhanced expression under salt stress. Subsequently, utilizing virus-induced gene silencing (VIGS) technology, we successfully silenced the two lncRNAs in cotton plants, which resulted in reduced expression levels of the corresponding target genes, rendering the plants less salt tolerant than did the control plants. Similarly, we successfully silenced these two target genes in cotton seedlings, and the silenced plants demonstrated a pronounced salt-sensitive phenotype. In summary, our transcriptome analysis revealed a significant number of differentially expressed lncRNAs and their corresponding coding genes. These findings lay the foundation for further investigating the mechanisms of lncRNAs and their target genes in the salt stress response of cotton.

GROWTH REGULATING FACTOR 7-mediated arbutin metabolism enhances rice salt tolerance.

Salt stress is an environmental factor that limits plant growth and crop production. With the rapid expansion of salinized arable land worldwide, investigating the molecular mechanisms underlying the salt stress response in plants is urgently needed. Here, we report that GROWTH REGULATING FACTOR 7 (OsGRF7) promotes salt tolerance by regulating arbutin (hydroquinone-β-D-glucopyranoside) metabolism in rice (Oryza sativa). Overexpression of OsGRF7 increased arbutin content, and exogenous arbutin application rescued the salt-sensitive phenotype of OsGRF7 knockdown and knockout plants. OsGRF7 directly promoted the expression of the arbutin biosynthesis genes URIDINE DIPHOSPHATE GLYCOSYLTRANSFERASE 1 (OsUGT1) and OsUGT5, and knockout of OsUGT1 or OsUGT5 reduced rice arbutin content, salt tolerance, and grain size. Furthermore, OsGRF7 degradation through its interaction with F-BOX AND OTHER DOMAINS CONTAINING PROTEIN 13 reduced rice salinity tolerance and grain size. These findings highlight an underexplored role of OsGRF7 in modulating rice arbutin metabolism, salt stress response, and grain size, as well as its broad potential use in rice breeding.

A Role for the Gastrointestinal Tract in Sodium Dysregulation Associated with the Salt Sensitive Phenotype in the Dahl S Rat

Introduction: Salt sensitive hypertension in the Dahl S rat (SS) has traditionally been attributed to elevated renal sodium reabsorption, largely mediated by the renal epithelial sodium channel (ENaC). Considering the role of ENaC in the distal colon epithelium in sodium absorption in the gastrointestinal tract, we hypothesized that the salt sensitive phenotype of SS rats may in part be attributable to increased absorption of sodium in the distal colon. Methods: Adult male SS and its control, the SR rats (12-14wo), were administered either low sodium diet (LS; 0.3% NaCl, Teklad) or moderately high sodium diet (HS; 2.0% NaCl, Teklad) ad libitum for two weeks. At endpoint, fecal samples were collected, dried for 72 hours at 70°C, weighed, and homogenized in deionized water. Fecal levels of sodium per gram of dry fecal weight were measured using flame photometry. Segments of distal colon wall were dissected and mounted in the Ussing chamber filled with warm, oxygenated Kreb’s solution containing D-glucose. Amiloride hydrochloride, a selective ENaC inhibitor, was applied to the tissue apical side in increasing concentrations (0-100μM) at 10-minute intervals. Total ionic currents (Isc, A) were measured under voltage clamp and presented as change from baseline. Results: We observed significantly lower fecal sodium levels in the SS compared to SR rats on LS diet (p<0.05), and a similar trend in fecal sodium levels between the SS and SR on HS diet (P=0.1). This was associated with significantly elevated amiloride-sensitive current in the distal colon of SS compared to the SR on LS and HS diets (p<0.01 and p<0.0001, respectively). Conclusion: Elevated amiloride-sensitive sodium current in the distal colon of SS rats is associated with decreased fecal sodium levels. This suggests increased sodium absorption in the SS rats and proposes a role for the gastrointestinal tract in sodium dysregulation associated with the salt sensitive phenotype in Dahl S rats. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

GhCLCc-1, a Chloride Channel Gene from Upland Cotton, Positively Regulates Salt Tolerance by Modulating the Accumulation of Chloride Ions.

The ionic toxicity induced by salinization has adverse effects on the growth and development of crops. However, researches on ionic toxicity and salt tolerance in plants have focused primarily on cations such as sodium ions (Na+), with very limited studies on chloride ions (Cl-). Here, we cloned the homologous genes of Arabidopsis thaliana AtCLCc, GhCLCc-1A/D, from upland cotton (Gossypium hirsutum), which were significantly induced by NaCl or KCl treatments. Subcellular localization showed that GhCLCc-1A/D were both localized to the tonoplast. Complementation of Arabidopsis atclcc mutant with GhCLCc-1 rescued its salt-sensitive phenotype. In addition, the silencing of the GhCLCc-1 gene led to an increased accumulation of Cl- in the roots, stems, and leaves of cotton seedlings under salt treatments, resulting in compromised salt tolerance. And ectopic expression of the GhCLCc-1 gene in Arabidopsis reduced the accumulation of Cl- in transgenic lines under salt treatments, thereby enhancing salt tolerance. These findings elucidate that GhCLCc-1 positively regulates salt tolerance by modulating Cl- accumulation and could be a potential target gene for improving salt tolerance in plants.

Positive Regulatory Roles of Manihot esculenta HAK5 under K+ Deficiency or High Salt Stress.

HAK/KUP/KT family members have been identified as playing key roles in K+ uptake and salt tolerance in numerous higher plants. However, their functions in cassava (Manihot esculenta Cantz) remain unknown. In this study, a gene encoding for a high-affinity potassium transporter (MeHAK5) was isolated from cassava and its function was investigated. Subcellular localization analysis showed that MeHAK5 is a plasma membrane-localized transporter. RT-PCR and RT-qPCR indicated that MeHAK5 is predominantly expressed in cassava roots, where it is upregulated by low potassium or high salt; in particular, its highest expression levels separately increased by 2.2 and 2.9 times after 50 µM KCl and 150 mM NaCl treatments. When heterologously expressed in yeast, MeHAK5 mediated K+ uptake within the cells of the yeast strain CY162 and rescued the salt-sensitive phenotype of AXT3K yeast. MeHAK5 overexpression in transgenic Arabidopsis plants exhibited improved growth and increased shoot K+ content under low potassium conditions. Under salt stress, MeHAK5 transgenic Arabidopsis plants accumulated more K+ in the shoots and roots and had reduced Na+ content in the shoots. As a result, MeHAK5 transgenic Arabidopsis demonstrated a more salt-tolerant phenotype. These results suggest that MeHAK5 functions as a high-affinity K+ transporter under K+ starvation conditions, improving K+/Na+ homeostasis and thereby functioning as a positive regulator of salt stress tolerance in transgenic Arabidopsis. Therefore, MeHAK5 may be a suitable candidate gene for improving K+ utilization efficiency and salt tolerance.

The OsWRKY72-OsAAT30/OsGSTU26 module mediates reactive oxygen species scavenging to drive heterosis for salt tolerance in hybrid rice.

Hybrid rice (Oryza sativa) generally outperforms its inbred parents in yield and stress tolerance, a phenomenon termed heterosis, but the underlying mechanism is not completely understood. Here, we combined transcriptome, proteome, physiological, and heterosis analyses to examine the salt response of super hybrid rice Chaoyou1000 (CY1000). In addition to surpassing the mean values for its two parents (mid-parent heterosis), CY1000 exhibited a higher reactive oxygen species scavenging ability than both its parents (over-parent heterosis or heterobeltiosis). Nonadditive expression and allele-specific gene expression assays showed that the glutathione S-transferase gene OsGSTU26 and the amino acid transporter gene OsAAT30 may have major roles in heterosis for salt tolerance, acting in an overdominant fashion in CY1000. Furthermore, we identified OsWRKY72 as a common transcription factor that binds and regulates OsGSTU26 and OsAAT30. The salt-sensitive phenotypes were associated with the OsWRKY72paternal genotype or the OsAAT30maternal genotype in core rice germplasm varieties. OsWRKY72paternal specifically repressed the expression of OsGSTU26 under salt stress, leading to salinity sensitivity, while OsWRKY72maternal specifically repressed OsAAT30, resulting in salinity tolerance. These results suggest that the OsWRKY72-OsAAT30/OsGSTU26 module may play an important role in heterosis for salt tolerance in an overdominant fashion in CY1000 hybrid rice, providing valuable clues to elucidate the mechanism of heterosis for salinity tolerance in hybrid rice.

Alternative oxidase 2 influences Arabidopsis seed germination under salt stress by modulating ABA signalling and ROS homeostasis

Seed germination is a critical checkpoint for plant survival under stresses, which requires functional mitochondria for energy and signal supply. Mitochondrial ALTERNATIVE OXIDASE 2 (AOX2) is specifically and highly expressed at early seed germination; however, its regulatory mechanism remains unknown. Here, the mutant (aox2), over-expression (AOX2OE) and complementation (aox2Comp, proAOX2::gAOX2/aox2) lines were used to investigate AOX2 roles. AOX2 transcript was significantly up-regulated under ABA, NaCl, H2O2, PEG6000 or mannitol treatments during seed germination. Compared with WT and aox2Comp, seed germination and greening were delayed in aox2 under NaCl treatment but enhanced in AOX2OE lines. The transcripts of key genes related to ABA biosynthesis and signal transduction were up-regulated in aox2 compared with those in WT under salt stress. Consequently, the higher ABA level was found in aox2. Na2WO4, the inhibitor of ABA biosynthesis, significantly enhanced germination rate of aox2. Mutation of ABA-INSENSITIVE 3 (ABI3) or ABI4 can partially reverse the salt-sensitive phenotypes of aox2. Yeast one-hybrid, D-luciferin enzyme (LUC) assay and transient expression experiments further revealed ABI3 and ABI4 can directly interact with AOX2 promoter and enhance its expression. Reactive oxygen species (ROS), mainly produced from the root tip mitochondria of germinated seeds, were accumulated more in aox2 than those in WT. Exogenous ascorbic acid (AsA) decreased ROS level and fully rescued the salt-hypersensitive phenotypes of aox2. Taken together, AOX2 plays an important role in Arabidopsis seed germination through regulating ABA signal and ROS homeostasis under salt stress; in the process, ABI3/ABI4 is indispensable for salinity-induced AOX2 expression.

Transcriptome profiles reveal NF-YC1-regulated pathways in adaption to salt stress in Arabidopsis thaliana

Salt stress is a major abiotic stress affecting plant growth and development. Identification and characterization of genes, especially for transcription factors (TFs), can provide us a comprehensive understanding of the regulatory mechanisms of transcriptional pathways in response to salt stress. Here, we first showed that nuclear-localized transcription factor nuclear factor-Y subunit C1 (NF-YC1) was required for the salt tolerance response in Arabidopsis. Loss of function of NF-YC1 resulted in a salt-sensitive phenotype together with increased sodium (Na) content in roots and shoots, while the overexpression line could complement this phenotype. Subsequent transcriptome analysis revealed differentially expressed genes (DEGs) in WT plants and nf-yc1 mutant, independent of salt treatment. Further analysis identified two positive downstream target genes AOX3 and BGLU47, involved in the cyanide-resistant alternative respiration and lignin biosynthesis, respectively, and a negative downstream target gene, MLS, which is related to malate synthase, as being involved in these regulatory cascades controlling the salt tolerance, and these results were further confirmed by CHIP-qPCR in vivo. In conclusion, several novel pathways have been elucidated, demonstrating that NF-YC1-dependent transcriptional regulation in salt-treated Arabidopsis thaliana.

Identification and functional verification of salt tolerance hub genes in Salix matsudana based on QTL and transcriptome analysis

Salt tolerance hub genes play a vital role in the response to salt stress. Exploring the salt tolerance hub genes of Salix matsudana (Koidz.), an allotetraploid willow with certain salt tolerance, will be conducive to further research on the molecular mechanism of salt tolerance in trees. Here, 114 F1 populations of crossing salt-tolerant willow "9901" and salt-sensitive willow "Yanjiang" were used to perform the QTL of salt-tolerant traits and transcriptome analysis. 46 QTLs related to salt tolerance traits were obtained, of which 9 QTLs can regulate multiple traits. A total of 23795 differentially expressed genes (DEGs) were obtained by RNA-seq in different salt treatment periods (0 h/4 h/8 h/12 h). Weighted gene co-expression network analysis (WGCNA) and time-ordered gene co-expression network (TO-GCN) analysis on these DEGs revealed candidate hub genes in regulating salt tolerance. Combining the QTL and transcriptome results, the number of salt tolerance hub genes was cut down and several hub genes were selected for further functional verification. qRT-PCR, VIGS and salt-sensitive yeast complementation experiment showed that the silencing of one of salt tolerance hub gene, SmERF B1–2 significantly reduced salt tolerance in S. matsudana. And the expression of SmERF B1–2 in salt-sensitive yeast strain AXT3K rescued its salt sensitive phenotype. In this study, the combination of QTL and transcriptome was shown to be effective in screening the salt-tolerant hub gene of S. matsudana. This salt-tolerant hub gene identified in this way provides new insight into the molecular mechanisms of salt tolerance in trees and a theoretical basis for molecular breeding of salt-tolerant trees.

Functional NADPH oxidase 2 in T cells amplifies salt-sensitive hypertension and associated renal damage.

Infiltrating T cells in the kidney amplify salt-sensitive (SS) hypertension and renal damage, but the mechanisms are not known. Genetic deletion of T cells (SSCD247-/-) or of the p67phox subunit of NADPH oxidase 2 (NOX2; SSp67phox-/-) attenuates SS hypertension in the Dahl SS rat. We hypothesized that reactive oxygen species produced by NOX2 in T cells drive the SS phenotype and renal damage. T cells were reconstituted by adoptively transferring splenocytes (∼10 million) from the Dahl SS (SS→CD247) rat, the SSp67phox-/- rat (p67phox→CD247), or only PBS (PBS→CD247) into the SSCD247-/- rat on postnatal day 5. Animals were instrumented with radiotelemeters and studied at 8 wk of age. There were no detectable differences in mean arterial pressure (MAP) or albuminuria between groups when rats were maintained on a low-salt (0.4% NaCl) diet. After 21 days of high-salt diet (4.0% NaCl), MAP and albuminuria were significantly greater in SS→CD247 rats compared with p67phox→CD247 and PBS→CD247 rats. Interestingly, there was no difference between p67phox→CD247 and PBS→CD247 rats in albuminuria or MAP after 21 days. The lack of CD3+ cells in PBS→CD247 rats and the presence of CD3+ cells in rats that received the T cell transfer demonstrated the effectiveness of the adoptive transfer. No differences in the number of CD3+, CD4+, or CD8+ cells were observed in the kidneys of SS→CD247 and p67phox→CD247 rats. These results indicate that reactive oxygen species produced by NOX2 in T cells participates in the amplification of SS hypertension and renal damage.NEW & NOTEWORTHY Our current work used the adoptive transfer of T cells that lack functional NADPH oxidase 2 into a genetically T cell-deficient Dahl salt-sensitive (SS) rat model. The results demonstrated that reactive oxygen species produced by NADPH oxidase 2 in T cells participate in the amplification of SS hypertension and associated renal damage and identifies a potential mechanism that exacerbates the salt-sensitive phenotype.

#4391 SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Abstract Background and Aims Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Method A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (P = .002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusion Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting.

Genome-wide identification and analysis of TCP family genes in Medicago sativa reveal their critical roles in Na+/K+ homeostasis

BackgroundMedicago sativa is the most important forage world widely, and is characterized by high quality and large biomass. While abiotic factors such as salt stress can negatively impact the growth and productivity of alfalfa. Maintaining Na+/K+ homeostasis in the cytoplasm helps reduce cell damage and nutritional deprivation, which increases a salt-tolerance of plant. Teosinte Branched1/ Cycloidea/ Proliferating cell factors (TCP) family genes, a group of plant-specific transcription factors (TFs), involved in regulating plant growth and development and abiotic stresses. Recent studies have shown TCPs control the Na+/K+ concentration of plants during salt stress. In order to improve alfalfa salt tolerance, it is important to identify alfalfa TCP genes and investigate if and how they regulate alfalfa Na+/K+ homeostasis.ResultsSeventy-one MsTCPs including 23 non-redundant TCP genes were identified in the database of alfalfa genome (C.V XinJiangDaYe), they were classified into class I PCF (37 members) and class II: CIN (28 members) and CYC/TB1 (9 members). Their distribution on chromosome were unequally. MsTCPs belonging to PCF were expressed specifically in different organs without regularity, which belonging to CIN class were mainly expressed in mature leaves. MsTCPs belongs to CYC/TB1 clade had the highest expression level at meristem. Cis-elements in the promoter of MsTCPs were also predicted, the results indicated that most of the MsTCPs will be induced by phytohormone and stress treatments, especially by ABA-related stimulus including salinity stress. We found 20 out of 23 MsTCPs were up-regulated in 200 mM NaCl treatment, and MsTCP3/14/15/18 were significantly induced by 10 μM KCl, a K+ deficiency treatment. Fourteen non-redundant MsTCPs contained miR319 target site, 11 of them were upregulated in MIM319 transgenic alfalfa, and among them four (MsTCP3/4/10A/B) genes were directly degraded by miR319. MIM319 transgene alfalfa plants showed a salt sensitive phenotype, which caused by a lower content of potassium in alfalfa at least partly. The expression of potassium transported related genes showed significantly higher expression in MIM319 plants. ConclusionsWe systematically analyzes the MsTCP gene family at a genome-wide level and reported that miR319-TCPs model played a function in K+ up-taking and/ or transportation especially in salt stress. The study provide valuable information for future study of TCP genes in alfalfa and supplies candidate genes for salt-tolerance alfalfa molecular-assisted breeding.

SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Objective: Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Design and method: A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results: No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (p = 0.002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusions: Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting