The transmembrane protein LbRSG from the recretohalophyte Limonium bicolor enhances salt gland development and salt tolerance.

Salt glands are the unique epidermal structures present in recretohalophytes, plants that actively excrete excess Na+ by salt secretory structures to avoid salt damage. Here, we describe a transmembrane protein that localizes to the plasma membrane of the recretohalophyte Limonium bicolor. As virus-induced gene silencing of the corresponding gene LbRSG in L. bicolor decreased the number of salt glands, we named the gene Reduced Salt Gland. We detected LbRSG transcripts in salt glands by in situ hybridization and transient transformation. Overexpression and silencing of LbRSG in L. bicolor pointed to a positive role in salt gland development and salt secretion by interacting with Lb3G16832. Heterologous LbRSG expression in Arabidopsis enhanced salt tolerance during germination and the seedling stage by alleviating NaCl-induced ion stress and osmotic stress after replacing or deleting the (highly) negatively charged region of extramembranous loop. After screened by immunoprecipitation-mass spectrometry and verified using yeast two-hybrid, PGK1 and BGLU18 were proposed to interact with LbRSG to strengthen salt tolerance. Therefore, we identified (highly) negatively charged regions in the extramembrane loop that may play an essential role in salt tolerance, offering hints about LbRSG function and its potential to confer salt resistance.

Global dynamics and cytokinin participation of salt gland development trajectory in recretohalophyte Limonium bicolor.

Salt gland is an epidermal Na+ secretory structure that enhances salt resistance in the recretohalophyte sea lavender (Limonium bicolor). To elucidate the salt gland development trajectory and related molecular mechanisms, we performed single-cell RNA sequencing of L. bicolor protoplasts from young leaves at salt gland initiation and differentiation stages. Dimensionality reduction analyses defined 19 transcriptionally distinct cell clusters, which were assigned into 4 broad populations-promeristem, epidermis, mesophyll, and vascular tissue-verified by in situ hybridization. Cytokinin was further proposed to participate in salt gland development by the expression patterns of related genes and cytological evidence. By comparison analyses of Single-cell RNA sequencing with exogenous application of 6-benzylaminopurine, we delineated 5 salt gland development-associated subclusters and defined salt gland-specific differentiation trajectories from Subclusters 8, 4, and 6 to Subcluster 3 and 1. Additionally, we validated the participation of TRIPTYCHON and the interacting protein Lb7G34824 in salt gland development, which regulated the expression of cytokinin metabolism and signaling-related genes such as GLABROUS INFLORESCENCE STEMS 2 to maintain cytokinin homeostasis during salt gland development. Our results generated a gene expression map of young leaves at single-cell resolution for the comprehensive investigation of salt gland determinants and cytokinin participation that helps elucidate cell fate determination during epidermis formation and evolution in recretohalophytes.

Global analysis of key post-transcriptional regulation in early leaf development of Limonium bicolor identifies a long non-coding RNA that promotes salt gland development and salt resistance.

Limonium bicolor, known horticulturally as sea lavender, is a typical recretohalophyte with salt glands in its leaf epidermis that secrete excess Na+ out of the plant. Although many genes have been proposed to contribute to salt gland initiation and development, a detailed analysis of alternative splicing, alternative polyadenylation patterns, and long non-coding RNAs (lncRNAs) has been lacking. Here, we applied single-molecule long-read mRNA isoform sequencing (Iso-seq) to explore the complexity of the L. bicolor transcriptome in leaves during salt gland initiation (stage A) and salt gland differentiation (stage B) based on the reference genome. We identified alternative splicing events and the use of alternative poly(A) sites unique to stage A or stage B, leading to the hypothesis that they might contribute to the differentiation of salt glands. Based on the Iso-seq data and RNA in situ hybridization of candidate genes, we selected the lncRNA Btranscript_153392 for gene editing and virus-induced gene silencing to dissect its function. In the absence of this transcript, we observed fewer salt glands on the leaf epidermis, leading to diminished salt secretion and salt tolerance. Our data provide abundant transcriptome resources for unraveling the mechanisms behind salt gland development and furthering crop transformation efforts towards enhanced survivability in saline soils.

Ferroelectric polarization promotes a CdS/In2Se3 heterostructure for photocatalytic water splitting.

The rapid recombination of photogenerated electrons and holes greatly limits the efficiency of photocatalyst based on semiconductor. In order to address this issue, we predicted a novel ferroelectric polarized heterojunction photocatalyst, CdS/In2Se3, which enables the spontaneous overall water splitting reaction. The CdS/In2Se3 heterojunction exhibits a band-edge staggered alignment and it is easy to form a direct Z-scheme charge transfer pathway. Besides, the built-in electric field (Eint) in the CdS/In2Se3 heterojunction promoted the charge transfer of CdS/In2Se3, leading to an improved separating efficiency of photo-generated carriers. Moreover, the vertical intrinsic polarized electric field (Ep) not only alters the position of the band edge but also reduces the bandgap limitations commonly associated with photocatalytic materials. Furthermore, the CdS/In2Se3 heterojunctions demonstrate separate catalytic activity for the hydrogen evolution reaction (HER) on the surface of the CdS monolayer and oxygen evolution reaction (OER) on the surface of In2Se3, respectively. Notably, the CdS/In2Se3-down configuration enables spontaneous photocatalytic water splitting in pH = 7, while the CdS/In2Se3-up configuration efficiently facilitates the HER process. This study highlights the significant advantages of CdS/In2Se3 heterojunctions as photocatalytic materials, offering unique insights into the development and research of this promising heterojunction architecture.

Theoretical Study on the Mechanisms and Kinetics of Atmospheric Oxidation of Tetrafluoropropyne and Its Analogues.

Tetrafluoropropyne (C3F4) is a potential dielectric in various electrical insulating equipment to replace the most potent industrial greenhouse gas, sulfur hexafluoride. Atmospheric oxidation of C3F4 by OH radicals in the presence of molecular O2 has been investigated theoretically in order to clarify the lifetime and degradation products at mechanistic and kinetic aspects. Energetic minimum-energy pathways for the C3F4 + OH/O2 reactions were calculated in detail using various theoretical methods including density functional M06-2X and CCSD for geometries, CBS-QB3, CCSD(T), and multireference RS2 with extrapolation to the complete basis-set limit for energies. It has been demonstrated that the C3F4 + OH reaction takes place via the bifurcated C-O addition/elimination routes leading to CF3C(OH)═CF and CF3C═C(OH)F radical adducts, where the latter is more preferable in view of the difference in barrier heights (1.3 vs 0.3 kcal/mol), followed by H-migration, HF-elimination, and C-C and C-F bond fission. The atmospheric lifetime of C3F4 was estimated to be about 13 days, which is indicative of a very short-lived substance in the atmosphere. Further degradation of the energy-rich C3F4OH* intermediates by O2 takes place spontaneously in view of the successive barrier-free and highly exothermic pathways, producing a variety of fluorinated acids, anhydrides, biacetyls, and regenerating OH radicals. For comparison, the reactions of C3H4, CF3CCH, and CH3CCF with OH radicals were examined to clarify the F-substitution effect. It is revealed that the reactivity of fluoropropynes could be either reduced by CF3 or enhanced by atomic F attached to the acetylenic carbon. The present work provides a fundamental understanding of the reactions of fluoroalkynes with OH/O2. The use of C3F4 as a promising eco-friendly gaseous dielectric alternative to SF6 has been supported.

Moniezia benedeni drives the SNAP-25 expression of the enteric nerves in sheep's small intestine.

BACKGROUND: The neuroimmune network plays a crucial role in regulating mucosal immune homeostasis within the digestive tract. Synaptosome-associated protein 25 (SNAP-25) is a presynaptic membrane-binding protein that activates ILC2s, initiating the host's anti-parasitic immune response. METHODS: To investigate the effect of Moniezia benedeni (M. benedeni) infection on the distribution of SNAP-25 in the sheep's small intestine, the recombinant plasmid pET-28a-SNAP-25 was constructed and expressed in BL21, yielding the recombinant protein. Then, the rabbit anti-sheep SNAP-25 polyclonal antibody was prepared and immunofluorescence staining was performed with it. The expression levels of SNAP-25 in the intestines of normal and M. benedeni-infected sheep were detected by ELISA. RESULTS: The results showed that the SNAP-25 recombinant protein was 29.3 KDa, the titer of the prepared immune serum reached 1:128,000. It was demonstrated that the rabbit anti-sheep SNAP-25 polyclonal antibody could bind to the natural protein of sheep SNAP-25 specifically. The expression levels of SNAP-25 in the sheep's small intestine revealed its primary presence in the muscular layer and lamina propria, particularly around nerve fibers surrounding the intestinal glands. Average expression levels in the duodenum, jejunum, and ileum were 130.32 pg/mg, 185.71 pg/mg, and 172.68 pg/mg, respectively. Under conditions of M. benedeni infection, the spatial distribution of SNAP-25-expressing nerve fibers remained consistent, but its expression level in each intestine segment was increased significantly (P < 0.05), up to 262.02 pg/mg, 276.84 pg/mg, and 326.65 pg/mg in the duodenum, jejunum, and ileum, and it was increased by 101.06%, 49.07%, and 89.16% respectively. CONCLUSIONS: These findings suggest that M. benedeni could induce the SNAP-25 expression levels in sheep's intestinal nerves significantly. The results lay a foundation for further exploration of the molecular mechanism by which the gastrointestinal nerve-mucosal immune network perceives parasites in sheep.

Structure-Activity Relationship Models to Predict Properties of the Dielectric Fluids for Transformer Insulation System.

Mineral oils and synthetic and natural esters are the predominant insulating liquids in electrical equipment. Structure-activity relationship models to predict the key properties of pure insulating liquids, including pulse breakdown strengths, AC breakdown voltages, dielectric constants, flash points, and kinematic viscosities, have been proposed for the first time. Dependence of the specific properties on the molecular structures has been illustrated quantitatively in terms of surface area, statistical total variance, and average deviation of positive and negative electrostatic potentials, as augmented by molecular weight, volume, and ovality. Moreover, the individual contribution of the functional groups to viscosity has been revealed by an additive approach. The predicted properties are in good agreement with the experimental data. The present theoretical work provides new insights on the development of novel dielectric fluids.

The RING zinc finger protein LbRZF1 promotes salt gland development and salt tolerance in Limonium bicolor.

The recretohalophyte Limonium bicolor thrives in high-salinity environments because salt glands on the above-ground parts of the plant help to expel excess salt. Here, we characterize a nucleus-localized C3HC4 (RING-HC)-type zinc finger protein of L. bicolor named  RING  ZINC  FINGER PROTEIN  1 (LbRZF1). LbRZF1 was expressed in salt glands and in response to NaCl treatment. LbRZF1 showed no E3 ubiquitin ligase activity. The phenotypes of overexpression and knockout lines for LbRZF1 indicated that LbRZF1 positively regulated salt gland development and salt tolerance in L. bicolor. lbrzf1 mutants had fewer salt glands and secreted less salt than did the wild-type, whereas LbRZF1-overexpressing lines had opposite phenotypes, in keeping with the overall salt tolerance of these plants. A yeast two-hybrid screen revealed that LbRZF1 interacted with LbCATALASE2 (LbCAT2) and the transcription factor LbMYB113, leading to their stabilization. Silencing of LbCAT2 or LbMYB113 decreased salt gland density and salt tolerance. The heterologous expression of LbRZF1 in Arabidopsis thaliana conferred salt tolerance to this non-halophyte. We also identified the transcription factor LbMYB48 as an upstream regulator of LbRZF1 transcription. The study of LbRZF1 in the regulation network of salt gland development also provides a good foundation for transforming crops and improving their salt resistance.

SbCASP-LP1C1 improves salt exclusion by enhancing the root apoplastic barrier.

Sweet sorghum [Sorghum bicolor (L.) Moench], a C4 crop with high biomass and strong resistance to multiple stresses, can grow and reproduce in saline-alkaline soil and is an ideal raw material for biofuels. Under high-salinity conditions, sweet sorghum shows extensive salt exclusion. However, the specific molecular mechanism of the apoplastic barrier in salt exclusion is unknown. In this study, SbCASP-LP1C1 (a CASP-like protein1C1) was localized in the plasma membrane of sweet sorghum root endodermal cells, and its function was further studied by heterologous expression in Arabidopsis (35 S:SbCASP-LP1C1-GFP). When germinated and grown on 50 mM NaCl, the SbCASP-LP1C1-expressing lines had longer roots and a higher salinity threshold compared with wild-type (Col-0) plant and the casp-lp T-DNA insertion mutant in Arabidopsis. The 35 S:SbCASP-LP1C1-GFP lines also suffered less oxidative damage as determined by DAB and NBT staining, and the expression levels of several antioxidant genes were higher in these lines. Moreover, the stele of 35 S:SbCASP-LP1C1-GFP lines was less permeable to propidium iodide, and these plants contained less Na+ in their shoots and roots compared to wild type and casp-lp. In the 35 S:SbCASP-LP1C1-GFP lines, the expression levels of two Casparian strip synthesis genes, MYB36 and ESB1, were increased. These results indicate that SbCASP-LP1C1 may be involved in the polymerization of lignin monomers in the Casparian strip of sweet sorghum, thereby regulating salt tolerance. These results provide a theoretical basis to understand the role of plant roots in salt exclusion and a means by which to improve the salt tolerance of crops.

Arabidopsis ZINC FINGER PROTEIN1 Acts Downstream of GL2 to Repress Root Hair Initiation and Elongation by Directly Suppressing bHLH Genes.

Cys2His2-like fold group (C2H2)-type zinc finger proteins promote root hair growth and development by regulating their target genes. However, little is known about their potential negative roles in root hair initiation and elongation. Here, we show that the C2H2-type zinc finger protein named ZINC FINGER PROTEIN1 (AtZP1), which contains an ERF-associated amphiphilic repression (EAR) motif, negatively regulates Arabidopsis (Arabidopsis thaliana) root hair initiation and elongation. Our results demonstrate that AtZP1 is highly expressed in root hairs and that AtZP1 inhibits transcriptional activity during root hair development. Plants overexpressing AtZP1 lacked root hairs, while loss-of-function mutants had longer and more numerous root hairs than the wild type. Transcriptome analysis indicated that AtZP1 downregulates genes encoding basic helix-loop-helix (bHLH) transcription factors associated with root hair cell differentiation and elongation. Mutation or deletion of the EAR motif substantially reduced the inhibitory activity of AtZP1. Chromatin immunoprecipitation assays, AtZP1:glucocorticoid receptor (GR) induction experiments, electrophoretic mobility shift assays, and yeast one-hybrid assays showed that AtZP1 directly targets the promoters of bHLH transcription factor genes, including the key root hair initiation gene ROOT HAIR DEFECTIVE6 (RHD6) and root hair elongation genes ROOT HAIR DEFECTIVE 6-LIKE 2 (RSL2) and RSL4, and suppresses root hair development. Our findings suggest that AtZP1 functions downstream of GL2 and negatively regulates root hair initiation and elongation, by suppressing RHD6, RSL4, and RSL2 transcription via the GL2/ZP1/RSL pathway.

The Arabidopsis Nodulin Homeobox Factor AtNDX Interacts with AtRING1A/B and Negatively Regulates Abscisic Acid Signaling.

The phytohormone abscisic acid (ABA) and the Polycomb group proteins have key roles in regulating plant growth and development; however, their interplay and underlying mechanisms are not fully understood. Here, we identified an Arabidopsis (Arabidopsis thaliana) nodulin homeobox (AtNDX) protein as a negative regulator in the ABA signaling pathway. AtNDX mutants are hypersensitive to ABA, as measured by inhibition of seed germination and root growth, and the expression of AtNDX is downregulated by ABA. AtNDX interacts with the Polycomb Repressive Complex1 (PRC1) core components AtRING1A and AtRING1B in vitro and in vivo, and together, they negatively regulate the expression levels of some ABA-responsive genes. We identified ABA-INSENSITIVE (ABI4) as a direct target of AtNDX. AtNDX directly binds the downstream region of ABI4 and deleting this region increases the ABA sensitivity of primary root growth. Furthermore, ABI4 mutations rescue the ABA-hypersensitive phenotypes of ndx mutants and ABI4-overexpressing plants are hypersensitive to ABA in primary root growth. Thus, our work reveals the critical functions of AtNDX and PRC1 in some ABA-mediated processes and their regulation of ABI4.

Mechanistic and Kinetic Investigations on Decomposition of Trifluoromethanesulfonyl Fluoride in the Presence of Water Vapor and Electric Field.

As a potential insulation gas to replace sulfur hexafluoride (SF6) due to environmental concerns, trifluoromethanesulonyl fluoride (CF3SO2F) has attracted great interests in various high-voltage electric applications. Thermal stability of CF3SO2F plays an important role in the rational design of the gas-insulated electric equipment. Unimolecular decomposition of CF3SO2F was investigated using high-level ab initio methods including the explicitly correlated RCCSD(T)-F12, the composite ROCBS-QB3, and the multireference RS2 extrapolated to complete basis set limit on the basis of M06-2X-, B2PLYPD3-, and CCSD-optimized geometrical parameters. Rate coefficients and decomposition temperatures were simulated using master equations. CF3SO2F decomposes predominantly via a simple C-S bond cleavage to form CF3 and SO2F, accompanied by a roaming induced F-abstraction detour to release CF4 and SO2, or isomerizes via CF3 migration to the more stable CF3OSFO followed by the production of CF2O and SOF2. Various characteristic decomposition products (e.g., CF4, C2F6, CF2O, SO2, SOF2, SO2F2, CF3H, and so on.) have been identified theoretically through secondary reactions and hydrolysis of CF3SO2F in the presence of water vapor. Electronic structures and stability of CF3SO2F could be affected significantly by the external electric field orientated along the S-C bond. The field-dependent electron-molecule capture rates support that CF3SO2F is superior to SF6 in dielectric strength. The present computational findings shed light on the practical use of CF3SO2F as the replacement gas for SF6.

Theoretical Characterizations on the Eco-Friendly Gas Tetrafluoropropyne for Electrical Insulation to Replace Sulfur Hexafluoride.

Gases for electric insulation are essential for various types of high-voltage power equipment. Sulfur hexafluoride (SF6) has been a dielectric medium commonly used in electrical grids for decades but it is the most potent industrial greenhouse gas. The continuous increase of SF6 emissions in the atmosphere exerts a significant impact on global warming. The identification of suitable drop-in replacements for all SF6-filled apparatuses has been elusive experimentally and theoretically. We claim that tetrafluoropropyne, C3F4, is a breakthrough in chemical alternatives to SF6. The performance of C3F4 was assessed systematically in a 6-dimensional manner, including dielectric strength, liquefaction temperature, global warming potential, thermal stability, toxicity, and arc interruption. On the basis of the extensive ab initio calculations, it has been demonstrated rigorously that C3F4 is an environmentally sustainable solution that may fulfill the complex combination of performance, stability, safety, and environmental properties, namely, the dielectric strength is about 50% higher than that of SF6, the boiling point is -50 °C, the GWP for 100 year time horizons is only 3, the decomposition temperature is above 600 °C, the toxicity is as low as HFOs, and the interruption capability is two-thirds of SF6. Two protocols are suggested for the practical use of C3F4. First, equivalence to 0.5 MPa SF6 could be obtained by filling 0.33 MPa C3F4 pure gas and lead minimum operating temperature down to -21 °C. Second, by taking advantage of synergism effect, the 40% C3F4/60% CO2 mixture is a viable alternative to SF6 with the operating temperature -30 °C without causing any environmental and safety concerns. The present theoretical work sheds new light on the challenging topic of the development of alternative dielectric gases and may stimulate experimental tests on the electrical applications of C3F4 in the future.

Theoretical Investigation on Atmospheric Chemistry of Nitryl Cyanide: A Novel Fluorine-Free Dielectric Gas.

In view of the significant greenhouse effect of sulfur hexafluoride and the potential biotoxic hazard of perfluorinated substances, we proposed that nitryl cyanide (NCNO2), a nearly nonpolar molecule with a unique combination of two strongly electronegative and polarized functional groups, is a novel fluorine-free replacement to be used as the insulating gas in green electrical grids. Atmospheric chemistry of NCNO2 has been investigated theoretically to assess its environmental impact if emitted into the atmosphere. Potential energy surfaces for the reaction of NCNO2 with OH in the presence of O2 were calculated using the restricted open-shell complete basis set quadratic Becke3 and Gaussian-4 methods on the basis of the density functional (M06-2X) and couple-cluster (CCSD) optimized geometrical parameters. The oxidation of NCNO2 takes place via the nearly zero-barrier association of OH with the cyano-C to form energy-rich adducts NC(OH)NO2, followed by C-N bond rupture to the major HOCN + NO2 and the minor HONO + NCO products. Interception of the adduct by O2 can result in OH-regeneration together with further degradation to CO and NOx. Moreover, photolysis of NCNO2 under tropospheric sunlight conditions might compete with OH-oxidation. The atmospheric lifetime and radiative efficiency of NCNO2 were computed to be far less than those of either nitriles or nitro compounds. The global warming potential of NCNO2 was estimated to be in the range of 0-5 for a 100 year time horizon. However, the secondary chemistry of NCNO2 should be treated with caution in view of the production of NOx in the atmosphere.

Computational Investigations on Reaction Mechanisms of the Covalent Inhibitors Ponatinib and Analogs Targeting the Extracellular Signal-Regulated Kinases.

As an important cancer therapeutic target, extracellular signal-regulated kinases (ERK) are involved in triggering various cellular responses in tumors. Regulation of the ERK signaling pathway by the small molecular inhibitors is highly desired for the sake of cancer therapy. In contrast to the routine inhibitors targeting ERKs through long-range non-bonding interactions, Ponatinib, a covalent inhibitor to ERK2 with a macrocyclic structure characterized by the α,ß-C=C unsaturated ketone, can form the stable -C(S)-C(H)-type complex via the four-center barrier due to the nucleophilic addition reaction of the thiol group of the Cys166 residue of ERK2 with the C=C double bond of Ponatinib with reaction free-energy barrier of 47.2 kcal/mol. Reaction mechanisms for the covalent binding were calculated using QM/MM methods and molecular dynamics simulations. The interaction modes and the corresponding binding free energies were obtained for the non-covalent and covalent complexation. The binding free energies of the non-covalent and covalent inhibitions are 14.8 kcal/mol and 33.4 kcal/mol, respectively. The mechanistic study stimulated a rational design on the modified Ponatinib structure by substituting the C=C bond with the C=N bond. It was demonstrated that the new compound exhibits better inhibition activity toward ERK2 in term of both thermodynamic and kinetic aspects through the covalent binding with a lower reaction free-energy barrier of 23.1 kcal/mol. The present theoretical work sheds new light on the development of the covalent inhibitors for the regulation of ERKs.

Optimization of Ethanol Extraction Technology for Yujin Powder Using Response Surface Methodology with a Box-Behnken Design Based on Analytic Hierarchy Process-Criteria Importance through Intercriteria Correlation Weight Analysis and Its Safety Evaluation.

Here, we aimed to optimize the ethanol extraction technology for Yujin powder (YJP) and evaluate its safety. The ultrasonic-assisted ethanol reflux extraction method refluxing was used to extract YJP. The parameters were optimized through a combination of single-factor and response surface methodology (RSM). The comprehensive Y value score calculated using the content of 13 active ingredients in YJP ethanolic extracts (YEEs) and the yield of the dry extract were used as measuring criteria. RSM with a Box-Behnken design using three factors and three levels was adopted to optimize the ethanol extraction technology for YJP. Finally, acute and subchronic toxicity tests were performed to evaluate its safety. The results revealed the best technological parameters: a liquid-material ratio of 24:1, an ethanol concentration of 69%, assistance of ultrasound (40 °C, 50 kHZ, 30 min), reflux time of 53 min, and reflux temperature of 50 °C. In acute toxicity tests, the maximum administration dosage in mice was 28.21 g/kg, which is higher than 10 times the clinical dosage. Adverse effects in the acute and subchronic toxicity tests were not observed. All clinical indexes were normal. In conclusion, the RSM based on AHP-CRITIC weight analysis could be used to optimize the ethanol extraction technology for YJP and YEEs prepared under the above conditions and ensure high safety.

Bracelet salt glands of the recretohalophyte Limonium bicolor: Distribution, morphology, and induction.

Halophytes complete their life cycles in saline environments. The recretohalophyte Limonium bicolor has evolved a specialized salt secretory structure, the salt gland, which excretes Na+ to avoid salt damage. Typical L. bicolor salt glands consist of 16 cells with four fluorescent foci and four secretory pores. Here, we describe a special type of salt gland at the base of the L. bicolor leaf petiole named bracelet salt glands due to their beaded-bracelet-like shape of blue auto-fluorescence. Bracelet salt glands contain more than 16 cells and more than four secretory pores. Leaf disc secretion measurements and non-invasive micro-test techniques indicated that bracelet salt glands secrete more salt than normal salt glands, which helps maintain low Na+ levels at the leaf blade to protect the leaf. Cytokinin treatment induced bracelet salt gland differentiation, and the developed ones showed no further differentiation when traced with a living fluorescence microscopy imager, even though new salt gland development and leaf expansion were observed. Transcriptome revealed a NAC transcription factor gene that participates in bracelet salt gland development, as confirmed by its genome editing and overexpression in L. bicolor. These findings shed light on bracelet salt gland development and may facilitate the engineering of salt-tolerant crops.

Integrative transcriptome and proteome analyses provide deep insights into the molecular mechanism of salt tolerance in Limonium bicolor.

KEY MESSAGE: Integrative transcriptome and proteome analyses revealed many candidate members that may involve in salt secretion from salt glands in Limonium bicolor. Limonium bicolor, a typical recretohalophyte, protects itself from salt damage by excreting excess salt out of its cells through salt glands. Here, to provide an overview of the salt-tolerance mechanism of L. bicolor, we conducted integrative transcriptome and proteome analyses of this species under salt treatment. We identified numerous differentially expressed transcripts and proteins that may be related to the salt-tolerance mechanism of L. bicolor. By measuring the Na+ secretion rate, were found that this cation secretion rate of a single salt gland was significantly increased after high salinity treatment compared with that in control and then reached the maximum in a short time. Interestingly, transcripts and proteins involved in transmembrane transport of ions were differentially expressed in response to high salinity treatment, suggesting a number of genes and proteins they may play important roles in the salt-stress response. Correlation between differentially expressed transcript and protein profiles revealed several transcripts and proteins that may be responsible for salt tolerance, such as cellulose synthases and annexins. Our findings uncovered many candidate transcripts and proteins in response to the salt tolerance of L. bicolor, providing deep insights into the molecular mechanisms of this important process in recretohalophytes.

Melatonin increases growth and salt tolerance of Limonium bicolor by improving photosynthetic and antioxidant capacity.

BACKGROUND: Soil salinization is becoming an increasingly serious problem worldwide, resulting in cultivated land loss and desertification, as well as having a serious impact on agriculture and the economy. The indoleamine melatonin (N-acetyl-5-methoxytryptamine) has a wide array of biological roles in plants, including acting as an auxin analog and an antioxidant. Previous studies have shown that exogenous melatonin application alleviates the salt-induced growth inhibition in non-halophyte plants; however, to our knowledge, melatonin effects have not been examined on halophytes, and it is unclear whether melatonin provides similar protection to salt-exposed halophytic plants. RESULTS: We exposed the halophyte Limonium bicolor to salt stress (300 mM) and concomitantly treated the plants with 5 µM melatonin to examine the effect of melatonin on salt tolerance. Exogenous melatonin treatment promoted the growth of L. bicolor under salt stress, as reflected by increasing its fresh weight and leaf area. This increased growth was caused by an increase in net photosynthetic rate and water use efficiency. Treatment of salt-stressed L. bicolor seedlings with 5 µM melatonin also enhanced the activities of antioxidants (superoxide dismutase [SOD], peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), while significantly decreasing the contents of hydrogen peroxide (H2O2), superoxide anion (O2•-), and malondialdehyde (MDA). To screen for L. bicolor genes involved in the above physiological processes, high-throughput RNA sequencing was conducted. A gene ontology enrichment analysis indicated that genes related to photosynthesis, reactive oxygen species scavenging, the auxin-dependent signaling pathway and mitogen-activated protein kinase (MAPK) were highly expressed under melatonin treatment. These data indicated that melatonin improved photosynthesis, decreased reactive oxygen species (ROS) and activated MAPK-mediated antioxidant responses, triggering a downstream MAPK cascade that upregulated the expression of antioxidant-related genes. Thus, melatonin improves the salt tolerance of L. bicolor by increasing photosynthesis and improving cellular redox homeostasis under salt stress. CONCLUSIONS: Our results showed that melatonin can upregulate the expression of genes related to photosynthesis, reactive oxygen species scavenging and mitogen-activated protein kinase (MAPK) of L. bicolor under salt stress, which can improve photosynthesis and antioxidant enzyme activities. Thus melatonin can promote the growth of the species and maintain the homeostasis of reactive oxygen species to alleviate salt stress.

6-Iodopurine as a Versatile Building Block for RNA Purine Architecture Modifications.

Natural modified bases in RNA were found to be indispensable for basic biological processes. In addition, artificial RNA modifications have been a versatile toolbox for the study of RNA interference, structure, and dynamics. Here, we present a chemical method for the facile synthesis of RNA containing C6-modified purine. 6-Iodopurine, as a postsynthetic building block with high reactivity, was used for metal-free construction of C-N, C-O, and C-S bonds under mild conditions and C-C bond formation by Suzuki-Miyaura cross-coupling. Our strategy provides a convenient approach for the synthesis of various RNA modifications, especially for oligonucleotides containing specific structures.