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Characterization of salt tolerance in ectoine-transformed tobacco plants (Nicotiana tabaccum): photosynthesis, osmotic adjustment, and nitrogen partitioning.

Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) biosynthetic genes (ect. ABC) from Halomonas elongata were introduced to tobacco plants using an Agrobacterium-mediated gene delivery system. The genes for ectoine biosynthesis were integrated in a stable manner into the tobacco genome and the corresponding transcripts were expressed. The concentration of ectoine under salt-stress conditions was higher in the roots than in leaves. A close relationship was found between stomatal conductance and the amount of transported nitrogen, suggesting that water transport through the xylem in the stem and transpiration may be involved in nitrogen transport to leaves. The data indicate that the turgor values of the ectoine transgenic lines increased with increasing salt concentration. The data revealed two ways in which ectoine enhanced salinity tolerance of tobacco plants. First, ectoine improved the maintenance of root function so that water is taken up consistently and supplied to shoots under saline conditions. Second, ectoine enhanced the nitrogen supply to leaves by increasing transpiration and by protecting Rubisco proteins from deleterious effects of salt, thereby improving the rate of photosynthesis.

Adaptation, Physiological↗

Salinity effect on growth and toxin production of four tropical Alexandrium species (Dinophyceae).

Four tropical PSP toxins-producing dinoflagellates, Alexandrium minutum, Alexandrium tamiyavanichii, Alexandrium tamarense and Alexandrium peruvianum from Malaysian waters were studied to investigate the influences of salinity on growth and toxin production. Experiments were conducted on constant temperature 25 degrees C, 140 microE mol m(-2) s(-1) and under 14:10 light:dark photo-cycle with salinity ranged from 2 to 30 psu. The PSP-toxin congeners, GTX 1-6, STX, dcSTX, NEO and C1-C2 were analysed by high performance liquid chromatography. Salinity tolerance of the four species in decreasing order is A. minutum>A. peruvianum>A. tamarense>A. tamiyavanichii. Specific growth rates and maximum densities varied among these species with A. minutum recorded as the highest, 0.5 day(-1) and 6 x 10(4) cells L(-1). Toxin content decreased with elevated salinities in A. minutum, the highest toxin content was about 12 fmole cell(-1) at 5 psu. In A. tamiyavanichii, toxin content peaked at optimal growth salinity (20 and 25 psu). Toxin content of A. tamarense, somehow peaked at sub-optimal growth salinity (15 and 30 psu). Results of this study implied that salinity fluctuation not only influenced the growth physiology but also toxin production of these species.

Animals↗

Analysis by two-dimensional electrophoresis of the effect of salt stress on the polypeptide patterns in roots of a salt-tolerant and a salt-sensitive cultivar of wheat.

The effect of salt stress on the polypeptide levels in roots of two wheat (Triticum durum) cultivars with different sensitivity to NaCl (cv. Ben Bachir, sensitive; cv. Chili, tolerant), was examined by two-dimensional polyacrylamide gel electrophoresis. Blue-stained gels were analyzed by visual inspection to identify changes that resulted when seedlings were grown in the presence of 200 mM NaCl for four days. Although the protein patterns for control and salt-stressed seedlings were qualitatively similar, the net synthesis of a 26 kDa polypeptide was significantly changed. This observation was mainly noticeable in the more tolerant cultivar. With the intention of identifying its function, the NH2-terminal of this polypeptide was sequenced. A 20 amino acid sequence was obtained and compared to sequences available in different databases. Possible roles of this polypeptide, depending on the homologies of its amino acid sequence with known proteins, in salinity tolerance are discussed.

Electrophoresis, Gel, Two-Dimensional↗

NaCl adaptation in Rana ridibunda and a comparison with the euryhaline toad Bufo viridis.

The physiological adaptation of the frog Rana ridibunda to saline environment was studied. It was found that blood was always hypertonic to the external solution, but at the highest salinity tolerated (i.e. 300 mOsM) the osmotic gradient across the skin was nearly abolished. Water uptake by the living frog remained unchanged, whereas sodium transport across the skin decreased markedly. Neurohypophyseal hormone increased water uptake and sodium transport to levels similar to those in tap water frogs. Water content of the tissues was not affected by saline adaptation, although it varied appreciably under acute conditions. Oxygen consumption increased in dehydrated frogs, but not in adapted ones. The results are discussed and compared to the euryhaline toad Bufo viridis; the importance of high urea levels for high salt adaptation is stressed.

Adaptation, Physiological↗

OmpW and OmpV are required for NaCl regulation in Photobacterium damsela.

Photobacterium damsela is a marine pathogen to both fish and human beings. The bacterium can shift between the ambient seawater and hosts, suggesting the existence of proteins rapidly responding to salt concentration. In the current study, proteomic methodologies were applied to screen the outer membrane proteins (OMPs) related to salt stress. OmpW and OmpV were determined in the response in this bacterium as OmpC and OmpF did in E. coli. Furthermore, the two genes were overexpressed in E. coli Top10F and complemented in V. paraheamolyticus mutants. The ability in salt-tolerance was elevated in the E. coli overexpressed OmpW and reduced in the cells overexpressed OmpV. These V. paraheamolyticus mutants could recover their response to environmental salt concentration when they were complemented by P. damsela OmpW and OmpV. These findings indicate that OmpW and OmpV are required for environmental salt regulation in P. damsela, in which OmpW and OmpV, respectively, elevate and reduce the ability in salinity-tolerance.

Bacterial Outer Membrane Proteins↗

Sediment toxicity tests using the burrowing amphipod Tiburonella viscana (Amphipoda: Platyischnopidae).

The present study investigated the feasibility of the use of the burrowing amphipod Tiburonella viscana for sediment toxicity assessments. The effects of reference toxicants, salinity, sediment particle size, and sediment contamination on amphipod survival were analyzed. The sensitivity of T. viscana to zinc, chromium, and sodium dodecyl sulfate (SDS) in acute tests was similar to that of other crustaceans. The 48-h LC(50) (lethal concentration to 50% of the test organisms in a 48-h exposure) values for T. viscana (95% confidence intervals in parenthesis) were 0.79 (0.56-1.12), 5.85 (4.9-7.0), and 3.41 (2.87-4.04) mg L(-1) for zinc, chromium, and SDS, respectively. The species tolerated salinity as low as 19 ppt under laboratory conditions, indicating its suitability for use in tests with some estuarine sediments. The survival of T. viscana was not affected by grain size in field-collected sediments ranging from 60.6% silt and clay to 95.5% sand, but survival was significantly reduced in laboratory-sieved sediments containing only one or two particle sizes, e.g., only medium and coarse sand, or medium sand, or fine sand, or only fines, suggesting that a mixed grain size distribution is necessary for amphipod survival.

Amphipoda↗

Transcriptional regulation and posttranslational activity of the betaine transporter BetL in Listeria monocytogenes are controlled by environmental salinity.

While the genetic elements contributing to the salinity tolerance of Listeria monocytogenes have been well characterized, the regulatory signals and responses (genetic and/or biochemical) that govern these mechanisms have yet to be elucidated. Encoded by betL, the first genetic element to be linked to listerial osmotolerance, the secondary betaine uptake system BetL is a member of the betaine-carnitine-choline transporter family. Preceded by consensus sigma(A)- and sigma(B)-dependent promoter sites, betL is constitutively expressed and transcriptionally up-regulated in response to salt stress. The nisin-controlled expression system was used to achieve salinity-independent, controlled betL expression in Listeria. In the absence of NaCl-activated transcriptional control, BetL activity was found to be a function of environmental salinity, showing optimal activity in buffer supplemented with 1 to 2% NaCl (osmolality, 417 to 719 mosmol/kg). In addition, BetL was activated rapidly (half-life, 2 min) in response to an osmotic upshift imposed by adding 2% NaCl to 50 mM potassium phosphate buffer.

Bacterial Proteins↗

Effect of saline acclimation on body water and sodium compartmentalization in Pekin ducks (Anas platyrhynchos).

The compartmentalization of body fluids was measured in individual Pekin ducks ( Anas platyrhynchos) drinking freshwater and after sequential acclimation to 300 mM NaCl and 400 mM NaCl. Total body water, extracellular fluid volume, plasma volume and exchangeable sodium pool were measured using (3)H(2)O, [(14)C]-polyethylene glycol, Evans Blue dye, and (22)Na dilution, respectively. Following acclimation to 300 mM NaCl, body mass decreased, but total body water and total exchangeable sodium pool were unaltered. Na and water were redistributed from the extracellular fluid (interstitial fluid) compartment into the intracellular fluid compartment. Following further acclimation to 400 mM NaCl, body mass, total body water and intracellular fluid volume decreased, but exchangeable sodium pool and extracellular fluid volume were unchanged. Our results suggested that, when Pekin ducks drink high but tolerable salinities, they maintain total body water, but redistribute Na(+) and water from interstitial fluid to the intracellular fluid compartment. When stressed beyond their ability to maintain total body water, they lose water from the intracellular fluid.

Acclimatization↗

Potential survival strategies of novel comammox and nitrite-oxidizing Nitrospira synthesizing osmoprotectants in a wastewater microbiome treating high-ammonia brackish landfill leachate.

BACKGROUND: In the late stages of landfill operation, leachate becomes brackish and contains high concentrations of ammonia with limited organic carbon. At leachate treatment facilities, it is typically subjected to nitrification followed by denitrification, with methanol supplied as an external electron donor. This unique environment may harbor novel microorganisms, including nitrifiers. Although a variety of microorganisms are involved in nitrification, their substrate specificity and salinity tolerance remain insufficiently understood. In this study, a genome-centric metagenome analysis was conducted on the microbiome from a leachate treatment facility at a closed landfill. RESULTS: A total of 68 metagenome-assembled genomes (MAGs) were reconstructed, including 64 putative novel species. Among these, two Nitrospira MAGs were recovered: a novel complete ammonia-oxidizing bacterium (comammox), Nitrospira LAS72 (88.72% completeness, 2.10% contamination), and canonical nitrite-oxidizing Nitrospira LAS18 (99.98% completeness, 2.29% contamination). Comparative genomic analysis with 260 publicly available Nitrospira genomes revealed that LAS18 represents a new sub-lineage within lineage VII of the Nitrospira genus. Two ammonia-oxidizing archaea (AOA), Candidatus Nitrosocosmicus LAS21 and Nitrosarchaeum LAS73, were also identified, while canonical ammonia-oxidizing bacteria were not detected. Given the brackish conditions (1.23% salinity) and the methanol-fed operation of the treatment facility, the genomic potential for osmotic stress adaptation and methanol metabolism was investigated. Comammox Nitrospira LAS72 harbors biosynthetic pathways for several compatible solutes (osmoprotectants), including glycine betaine, proline, trehalose, and L-glutamate. Moreover, comammox Nitrospira LAS72 possesses genetic potential for oxidizing formaldehyde, suggesting that it may exploit these methanol-derived intermediates as energy sources. These features indicate that LAS72 may withstand osmotic fluctuations through the production of various osmoprotectants and thrive under the unique conditions of a methanol-fed environment. CONCLUSIONS: The discovery of novel comammox Nitrospira and canonical Nitrospira forming a new sub-lineage within lineage VII of the Nitrospira genus in an ammonia-rich brackish environment provides the first genomic evidence for evolutionary adaptation among nitrifiers to saline, methanol-fed environments. These findings enhance our understanding of the ecological and evolutionary dynamics shaping nitrifier communities in complex treatment ecosystems. Video Abstract.

Ammonia↗

Comparative sensitivity of gametes and early developmental stages of a sea urchin species (Echinometra mathaei) and a bivalve species (Isognomon californicum) during metal exposures.

Bioassays were developed using sperm of a sea urchin (Echinometra mathaei), and sperm, embryos, and larvae of a bivalve species (Isognomon californicum). Sea urchin spawning was restricted to only a few months of the year and viability of sperm throughout the year varied from 5 to 75%. Sea urchin fertilization assays were affected by temporal variation in sperm viability. Spawning in this bivalve species occurs year-round and there is little temporal variation in sperm viability. Since stringent sperm:egg ratios are not required for the bivalve embryo and larval assays, these were less affected by variation in gamete quality. The relative sensitivity of the various assays were compared during exposure to three different metal pollutants: cadmium, copper, and tributyltin. Gametes and embryos were relatively resistant to cadmium toxicity, but larvae were very sensitive. With copper and tributyltin, sea urchin and bivalve fertilization assays were the least sensitive; and bivalve growth assays were the most sensitive, followed closely by the bivalve embryo assays. On the basis of sensitivity, ease and time required to conduct the assay, and salinity tolerance, the bivalve embryo assay was recommended as the overall single most reliable toxicity bioassay. However a multispecies, multidimensional approach using sperm fertilization assays as well as embryo assays should be employed, perhaps in a hierarchal manner. Larval growth assays were deemed too tedious and time consuming to be used routinely, but due to their high sensitivity, should still be considered as a valuable comparative tool.

Animals↗

Starch-hydrolyzing bacteria from Ethiopian soda lakes.

Alkaliphilic bacteria were isolated from soil and water samples obtained from Ethiopian soda lakes in the Rift Valley area--Lake Shala, Lake Abijata, and Lake Arenguadi. Starch-hydrolyzing isolates were selected on the basis of their activity on starch agar plate assay. Sixteen isolates were chosen, characterized, and subjected to 16S rRNA gene sequence analysis. All the isolates were gram positive and catalase- and beta-galactosidase positive. All isolates except one were motile endospore-forming rods and were found to be closely related to the Bacillus cluster, being grouped with Bacillus pseudofirmus, Bacillus cohnii, Bacillus vedderi, and Bacillus agaradhaerens. The one exception had nonmotile coccoid cells and was closely related to Nesterenkonia halobia. The majority of the isolates showed optimal growth at 37 degrees C and tolerated salinity up to 10% (w/v) NaCl. Both extracellular and cell-bound amylase activity was detected among the isolates. The amylase activity of two isolates, related to B. vedderi and B. cohnii, was stimulated by ethylenediaminetetraacetic acid (EDTA) and inhibited in the presence of calcium ions. Pullulanase activity was expressed by isolates grouped with B. vedderi and also most of the isolates clustered with B. cohnii; cyclodextrin glycosyltransferase was expressed by most of the B. agaradhaerens-related strains. Minor levels of alpha-glucosidase activity were detected in all the strains.

Amylose↗

Neoplastic hypercalcemia: physiologic response to intravenous etidronate disodium.

Following a four-day control period during which an elevated serum calcium level either stabilized or continued to rise despite maximally tolerated saline diuresis, 12 patients with neoplastic hypercalcemia were treated with intravenous etidronate disodium (etidronate) 7.5 mg/kg/day for up to seven days. Serum calcium reverted to normal levels in all patients, with the mean pretreatment serum calcium level of 12.5 +/- 0.4 mg/dl dropping to 9.2 +/- 0.2 mg/dl (p less than 0.01) by Day 7. Elevated urinary calcium (1,107 +/- 134 mg/g creatinine) and hydroxyproline levels (154 +/- 16 mg/g creatinine) declined to 245 +/- 52 mg/g creatinine and 75 +/- 14 mg/g creatinine, respectively, suggesting a marked reduction in bone resorption following treatment. Serum phosphorus levels were unchanged, but urinary phosphorus levels dropped rapidly from 1,181 +/- 125 mg/g creatinine before treatment to 723 +/- 94 mg/g creatinine after two days. Serum parathyroid hormone levels (mid-molecule assay) were suppressed before treatment (64 +/- 16 pg/ml), but rose rapidly to 223 +/- 68 pg/ml by Day 7 of treatment. The value of serum 1,25-dihydroxyvitamin D was initially below normal (16 +/- 3 pg/ml), but rose rapidly with treatment to 42 +/- 12 pg/ml by Day 7. Symptoms of hypercalcemia and bone pain improved with treatment, and no serious adverse reactions to treatment were encountered. Intravenous etidronate is apparently an effective and safe treatment for neoplastic hypercalcemia.

Adult↗

The role of cortisol and growth hormone in seawater adaptation and development of hypoosmoregulatory mechanisms in sea trout parr (Salmo trutta trutta).

The role of growth hormone (GH) and cortisol in the development of hypoosmoregulatory mechanisms in sea trout parr, Salmo trutta trutta, was investigated by injecting freshwater (FW) yearlings every second day with saline, ovine growth hormone (oGH, 2.0 micrograms/g), cortisol (hydrocortisone hemisuccinate, 8.0 micrograms/g), or oGH + cortisol for a maximum of 14 days. Subgroups of the treated fish were transferred to three-fourths seawater (SW) after 7 or 15 days of treatment and the effects on plasma Na+, Cl-, muscle water content, gill Na+/K(+)-ATPase activity, and gill interlamellar chloride cell density were examined. In FW, gill Na+/K(+)-ATPase chloride cell density, and chloride cell apical to basal length increased by all hormone treatments, most significant by oGH + cortisol treatment. Plasma ions and muscle water content were unaffected in FW. Both SW transfers resulted in considerable mortality (50%) in control fish, whereas few cortisol-treated and no GH-treated or GH + cortisol-treated fish died. Plasma Na+ and Cl- levels increased dramatically (greater than 50%) in control fish and muscle water content decreased (8%) on Day 2 after both transfers. All hormone-treated groups regulated plasma ions and muscle water significantly better than controls in SW, indicating the physiological significance of the treatment. Notably, the oGH + cortisol-treated fish showed only insignificant changes in ion-osmotic homeostasis after SW transfer, suggesting a synergistic effect of the two hormones. It is concluded that treatment with the two hormones increases the salinity tolerance of sea trout parr at a developmental stage where FW life is obligatory.

Adaptation, Physiological↗

Seasonal changes in seawater adaptability and plasma levels of prolactin and growth hormone in landlocked sockeye salmon (Oncorhynchus nerka) and amago salmon (O. rhodurus).

In order to clarify the roles of prolactin (PRL) and growth hormone (GH) in the development of seawater adaptability in salmonids, seasonal changes in salinity tolerance, plasma PRL, and plasma GH were examined in juvenile landlocked sockeye salmon (Oncorhynchus nerka) and amago salmon (O. rhodurus). Assessed by the 24-hr seawater-challenge test, the landlocked sockeye salmon possessed seawater adaptability as underyearlings in spring, which was maintained throughout the year, and a further increase was observed as yearlings the next spring. An increase in seawater adaptability was observed in silvery juvenile amago salmon as underyearlings from autumn to winter, when some of the wild population migrate to the sea. Precociously mature amago salmon, which did not develop a silvery body color but maintained distinct parr marks, also showed an improvement in seawater adaptability during autumn to winter, although plasma sodium levels after transfer to seawater were still higher than those of the silvery juveniles. In both sockeye and amago salmon, seasonal changes in plasma levels of PRL and GH were not correlated with development of seawater adaptability. In both species, acclimation to seawater resulted in decreased plasma levels of PRL irrespective of their adaptability to seawater, in agreement with the inhibitory effects of PRL in seawater adaptation. On the other hand, plasma GH levels increased only when seawater adaptability was high, in agreement with previous observations indicating an important role of GH in seawater adaptation of salmonids.

Adaptation, Physiological↗

Ancyrocephaline monogeneans of the genera Chauhanellus and Hamatopeduncularia from the gills of the blue catfish, Arius graeffei, in the Brisbane River and Moreton Bay, Queensland, Australia, with descriptions of four new species.

At least six ancyrocephaline monogeneans, four of which are new species, are reported from the gills of the blue catfish, Arius graeffei, in the Brisbane area, Queensland, Australia, namely Chauhanellus australis (Young, 1967) Bychowsky & Nagibina, 1969, Chauhanellus youngi new species, Hamatopeduncularia pearsoni new species, Hamatopeduncularia brisbanensis Young, 1967, Hamatopeduncularia major new species and Hamatopeduncularia spiralis new species. H. major has been found so far only on catfishes from the Brisbane River (freshwater) and C. youngi and H. brisbanensis only on catfishes from Moreton Bay (salt water). H. spiralis is described from river catfishes; a similar, possibly identical parasite occurs on bay catfishes. Young's paratypes of H. brisbanensis were found to include specimens of H. pearsoni new species. Additional observations were made on the anatomy and biology of C. australis and H. brisbanensis, with special attention being paid to the haptor glands. New light is shed on the function of the marginal-hooklet-bearing haptoral tentacles of Hamatopeduncularia spp. and on the status of these tentacles in taxonomic studies. Possible evolutionary trends in these gill parasites are suggested. Consideration is given to salinity tolerances by the parasites, to possible age-related changes in host susceptibility and to genetic differences between catfishes, as explanations for differences in the distribution of these parasites on large and small hosts and on hosts from the Brisbane River and from Moreton Bay.

Animals↗

Biodegradation of diesel oil by an Arabian Sea sediment culture isolated from the vicinity of an oil field.

Laboratory scale batch studies were performed to test the diesel oil biodegradation ability of ES1 cultures isolated from Arabian Sea sediments obtained from the vicinity of an oil field. This culture could utilize diesel as the sole source of carbon and energy. Under aerobic conditions, 39% loss of diesel oil was observed over 8 days where 80% of the loss was due to aliphatic constituents. Under anoxic nitrate reducing conditions the rate and extent of degradation was significantly lower, i.e., 18% over 50 days. Salt acclimatized cultures could tolerate salinities up to 3.5% and demonstrated optimal performance at a salinity of 0.5%. The optimum N/P ratio for these cultures was found to be in the range of 2:1-5:1. Addition of two trace elemental substance formulations exhibited a significant inhibitory effect on culture growth. This culture has good potential for decontamination of oil-contaminated marine and subsurface environments.

Bacteria↗

Transcript profiling of salinity stress responses by large-scale expressed sequence tag analysis in Mesembryanthemum crystallinum.

The common ice plant, Mesembryanthemum crystallinum, is a halophytic (salt-loving) member of the Aizoaceae, which switches from C3 photosynthesis to Crassulacean acid metabolism (CAM) when exposed to salinity or water-deficit stress. CAM is a metabolic adaptation of photosynthetic carbon fixation that improves water use efficiency by shifting net CO2 uptake to the night, thereby reducing transpirational water loss. To improve our understanding of the molecular genetic underpinnings and control mechanisms for Crassulacean acid metabolism (CAM) and other salinity stress response adaptations, a total of 9733 expressed sequence tags (ESTs) from cDNAs derived from leaf tissues of well-watered and salinity-stressed (0.5 M NaCl for 30 and 48 h) were characterized. Clustering and assembly of these ESTs resulted in the identification of a total of 3676 tentative unique gene sequences (1249 tentative consensus sequences and 2427 singleton ESTs) expressed in leaves of ice plant under unstressed and salinity stressed conditions. The same number (2782) of ESTs from each library (total=8346 ESTs) were randomly selected and analyzed to compare expression profiles among the control and salt stressed leaf tissues. EST frequencies for transcripts encoding CAM-related enzymes, pathogenesis-related, senescence-associated, cell death-related, and stress-related proteins such as heat shock proteins (HSPs), chaperones, early light-inducible proteins, ion homeostasis, antioxidative stress, detoxification, and biosynthetic enzymes for osmoprotectants increased 2-12-fold in cDNA libraries constructed from salt stressed plants. In contrast, the frequency of ESTs encoding light-harvesting and photosystem complexes and C3 photosynthetic enzymes decreased 4-fold overall following salinity stress with transcripts for ribulose bisphosphate carboxylase/oxygenase (RuBisCO) subunits decreasing 7-fold. Moreover, stressed plants contained a higher percentage of ESTs encoding novel and/or functionally unknown proteins. The rapid discovery of both known and unknown genes related to stress responses in M. crystallinum demonstrates the great utility of EST analysis in unraveling the complex set of adaptive mechanisms contributing to water use efficiency (CAM) and salinity tolerance.

Cluster Analysis↗

Comparative phylogenomics and transcriptional regulatory networks of AQPs, HSPs, and LEA proteins in salt-stressed Portulaca oleracea.

Soil salinization severely threatens global food security, necessitating systematic investigations of halophytes like Portulaca oleracea to decode the molecular mechanisms of environmental resilience. Utilizing an integrated framework of deep learning-based genome annotation (58,817 predicted genes; 96.5% BUSCO completeness), multi-tissue RNA-Seq, phylogenomics, and gene regulatory network (GRN) inference, the synergistic orchestration of 78 aquaporins (AQPs), 525 heat shock proteins (HSPs), and 119 late embryogenesis abundant (LEA) proteins was elucidated. The active transcriptome, encompassing 39,065 expressed loci, revealed a systemic growth-defense trade-off. Tissues displayed distinct adaptive mechanisms: leaves modulated intracellular water balance via specialized AQPs, whereas adult roots maintained proteostasis through robust HSP20/HSP70 induction. Phylogenomic clustering across 154 species demonstrated that salinity tolerance constitutes an evolutionary mosaic, identifying 81 halophyte-exclusive orthogroups and 1129 species-specific clusters. Comparative topology across six independent GRNs (4.2M-5.3 M edges) unmasked a highly modular transcriptional reprogramming strategy governed by a core apparatus of 22 stress-exclusive regulators, with functional enrichment heavily prioritizing protein dimerization and chromatin remodeling. Theoretically, the distinct convergence of Trihelix transcription factors with guard cell differentiation pathways offers a candidate transcriptomic framework to explain the plant's characteristic C4-CAM photosynthetic plasticity under severe osmotic pressure. Practically, these evolutionary blueprints and specific master switches transcend single-gene transgenic limitations. Utilizing these root-sustained and stress-inducible targets under localized promoters provides a naturally optimized, network-level precision engineering roadmap to transfer robust, compartmentalized halotolerance to sensitive glycophytic crops.

Gene Regulatory Networks↗