NADPH oxidase-dependent H2O2 production mediates salicylic acid-induced salt tolerance in mangrove plant Kandelia obovata by regulating Na+/K+ and redox homeostasis.

Salicylic acid (SA) is known to enhance salt tolerance in plants. However, the mechanism of SA-mediated response to high salinity in halophyte remains unclear. Using electrophysiological and molecular biological methods, we investigated the role of SA in response to high salinity in mangrove species, Kandelia obovata, a typical halophyte. Exposure of K. obovata roots to high salinity resulted in a rapid increase in endogenous SA produced by phenylalanine ammonia lyase pathway. The application of exogenous SA improved the salt tolerance of K. obovata, which depended on the NADPH oxidase-mediated H2O2. Exogenous SA and H2O2 increased Na+ efflux and reduced K+ loss by regulating the transcription levels of Na+ and K+ transport-related genes, thus reducing the Na+/K+ ratio in the salt-treated K. obovata roots. In addition, exogenous SA-enhanced antioxidant enzyme activity and its transcripts, and the expressions of four genes related to AsA-GSH cycle as well, then alleviated oxidative damages in the salt-treated K. obovata roots. However, the above effects of SA could be reversed by diphenyleneiodonium chloride (the NADPH oxidase inhibitor) and paclobutrazol (a SA biosynthesis inhibitor). Collectively, our results demonstrated that SA-induced salt tolerance of K. obovata depends on NADPH oxidase-generated H2O2 that affects Na+/K+ and redox homeostasis in response to high salinity.

PlantC2U: deep learning of cross-species sequence landscapes predicts plastid C-to-U RNA editing in plants.

In plants, C-to-U RNA editing mainly occurs in plastid and mitochondrial transcripts, which contributes to a complex transcriptional regulatory network. More evidence reveals that RNA editing plays critical roles in plant growth and development. However, accurate detection of RNA editing sites using transcriptome sequencing data alone is still challenging. In the present study, we develop PlantC2U, which is a convolutional neural network, to predict plastid C-to-U RNA editing based on the genomic sequence. PlantC2U achieves >95% sensitivity and 99% specificity, which outperforms the PREPACT tool, random forests, and support vector machines. PlantC2U not only further checks RNA editing sites from transcriptome data to reduce possible false positives, but also assesses the effect of different mutations on C-to-U RNA editing based on the flanking sequences. Moreover, we found the patterns of tissue-specific RNA editing in the mangrove plant Kandelia obovata, and observed reduced C-to-U RNA editing rates in the cold stress response of K. obovata, suggesting their potential regulatory roles in plant stress adaptation. In addition, we present RNAeditDB, available online at https://jasonxu.shinyapps.io/RNAeditDB/. Together, PlantC2U and RNAeditDB will help researchers explore the RNA editing events in plants and thus will be of broad utility for the plant research community.

Inventory of cadmium-transporter genes in the root of mangrove plant Avicennia marina under cadmium stress.

Mangrove Avicennia marina has the importantly potential for cadmium (Cd) pollution remediation in coastal wetlands. Unfortunately, the molecular mechanisms and transporter members for Cd uptake by the roots of A. marina are not well documented. In this study, photosynthetic and phenotypic analysis indicated that A. marina is particularly tolerant to Cd. The content and flux analysis indicated that Cd is mainly retained in the roots, with greater Cd influx in fine roots than that in coarse roots, and higher Cd influx in the root meristem zone as well. Using transcriptomic analysis, a total of 5238 differentially expressed genes were identified between the Cd treatment and control group. Moreover, we found that 54 genes were responsible for inorganic ion transport. Among these genes, AmHMA2, AmIRT1, and AmPCR2 were localized in the plasma membrane and AmZIP1 was localized in both plasma membrane and cytoplasm. All above gene encoding transporters showed significant Cd transport activities using function assay in yeast cells. In addition, the overexpression of AmZIP1 or AmPCR2 in Arabidopsis improved the Cd tolerance of transgenic plants. This is particularly significant as it provides insight into the molecular mechanism for Cd uptake by the roots of mangrove plants and a theoretical basis for coastal wetland phytoremediation.

Integration of eQTL and GWAS analysis uncovers a genetic regulation of natural ionomic variation in Arabidopsis.

KEY MESSAGE: This study provided important insights into the genetic architecture of variations in A. thaliana leaf ionome in a cell-type-specific manner. The functional interpretation of traits associated variants by expression quantitative trait loci (eQTL) analysis is usually performed in bulk tissue samples. While the regulation of gene expression is context-dependent, such as cell-type-specific manner. In this study, we estimated cell-type abundances from 728 bulk tissue samples using single-cell RNA-sequencing dataset, and performed cis-eQTL mapping to identify cell-type-interaction eQTL (cis-eQTLs(ci)) in A. thaliana. Also, we performed Genome-wide association studies (GWAS) analyses for 999 accessions to identify the genetic basis of variations in A. thaliana leaf ionome. As a result, a total of 5,664 unique eQTL genes and 15,038 unique cis-eQTLs(ci) were significant. The majority (62.83%) of cis-eQTLs(ci) were cell-type-specific eQTLs. Using colocalization, we uncovered one interested gene AT2G25590 in Phloem cell, encoding a kind of plant Tudor-like protein with possible chromatin-associated functions, which colocalized with the most significant cis-eQTL(ci) of a Mo-related locus (Chr2:10,908,806:A:C; P = 3.27 × 10-27). Furthermore, we prioritized eight target genes associated with AT2G25590, which were previously reported in regulating the concentration of Mo element in A. thaliana. This study revealed the genetic regulation of ionomic variations and provided a foundation for further studies on molecular mechanisms of genetic variants controlling the A. thaliana ionome.

[Research progress of histone acetylation in prevention and treatment of heart failure and new ideas based on traditional Chinese medicine].

Chronic heart failure(CHF) has become a worldwide public health problem due to its high morbidity and mortality, which seriously endangers people's lifespan and quality of life. In recent years, the treatment strategy of CHF has shifted its emphasis on short-term improvement and transformation of hemodynamics to long-term repair as well as improvement of the biological properties of heart failure. At present, with the continuous deepening of medical research, it has been found that histone acetylation is closely related to the occurrence and development of CHF. Traditional Chinese medicine, via regulating histone acetylation, delays ventricular remodeling, improves energy metabolism, inhibits fibrosis and cardiomyocyte hypertrophy, and intervenes in the development process of heart failure, thus reducing the mortality and the readmission rate and ultimately improving long-term prognosis. Therefore, this study reviewed the mechanism of histone acetylation in the treatment of heart failure as well as its prevention and treatment with traditional Chinese medicine, to provide reference for clinical treatment of CHF.

Proteomic analysis reveals differential responsive mechanisms in Solanum nigrum exposed to low and high dose of cadmium.

Cadmium (Cd) contamination is becoming a widespread environmental problem. However, the differential responsive mechanisms of Cd hyperaccumulator Solanum nigrum to low or high dose of Cd are not well documented. In this study, phenotypic and physiological analysis firstly suggested that the seedlings of S. nigrum showed slight leaf chlorosis symptoms under 25 µM Cd and severe inhibition on growth and photosynthesis under 100 µM Cd. Further proteomic analysis identified 105 differentially expressed proteins (DEPs) in the Cd-treated leaves. Under low dose of Cd stress, 47 DEPs are mainly involved in primary metabolic processes, while under high dose of Cd stress, 92 DEPs are mainly involved in photosynthesis, energy metabolism, production of phytochelatin and reactive oxygen species (ROS). Protein-protein interaction (PPI) network analysis of DEPs support above differential responses in the leaves of S. nigrum to low and high dose of Cd treatments. This work provides the differential responsive mechanisms in S. nigrum to low and high dose of Cd, and the theoretical foundation for the application of hyperaccumulating plants in the phytoremediation of Cd-contaminated soils.

Leaf sodium homeostasis controlled by salt gland is associated with salt tolerance in mangrove plant Avicennia marina.

Avicennia marina, a mangrove plant growing in coastal wetland habitats, is frequently affected by tidal salinity. To understand its salinity tolerance, the seedlings of A. marina were treated with 0, 200, 400 and 600 mM NaCl. We found the whole-plant dry weight and photosynthetic parameters increased at 200 mM NaCl but decreased over 400 mM NaCl. The maximum quantum yield of primary photochemistry (Fv/Fm) significantly decreased at 600 mM NaCl. Transmission electron microscopy observations showed high salinity caused the reduction in starch grain size, swelling of the thylakoids and separation of the granal stacks, and even destruction of the envelope. In addition, the dense protoplasm and abundant mitochondria in the secretory and stalk cells, and abundant plasmodesmata between salt gland cells were observed in the salt glands of the adaxial epidermis. At all salinities, Na+ content was higher in leaves than in stems and roots; however, Na+ content increased in the roots while it remained at a constant level in the leaves over 400 mM NaCl treatment, due to salt secretion from the salt glands. As a result, salt crystals on the leaf adaxial surface increased with salinity. On the other hand, salt treatment increased Na+ and K+ efflux and decreased H+ efflux from the salt glands by the non-invasive micro-test technology, although Na+ efflux reached the maximum at 400 mM NaCl. Further real-time quantitative PCR analysis indicated that the expression of Na+/H+ antiporter (SOS1 and NHX1), H+-ATPase (AHA1 and VHA-c1) and K+ channel (AKT1, HAK5 and GORK) were up-regulated, and only the only Na+ inward transporter (HKT1) was down-regulated in the salt glands enriched adaxial epidermis of the leaves under 400 mM NaCl treatment. In conclusion, salinity below 200 mM NaCl was beneficial to the growth of A. marina, and below 400 mM, the salt glands could excrete Na+ effectively, thus improving its salt tolerance.

Chlorophyll f production in two new subaerial cyanobacteria of the family Oculatellaceae.

Chlorophyll (Chl) f was recently identified in a few cyanobacteria as the fifth chlorophyll of oxygenic organisms. In this study, two Leptolyngbya-like strains of CCNU0012 and CCNU0013 were isolated from a dry ditch in Chongqing city and a brick wall in Mount Emei Scenic Area in China, respectively. These two strains were described as new species: Elainella chongqingensis sp. nov. (Oculatellaceae, Synechococcales) and Pegethrix sichuanica sp. nov. (Oculatellaceae, Synechococcales) by the polyphasic approach based on morphological features, phylogenetic analysis of 16S rRNA gene and secondary structure comparison of 16S-23S internal transcribed spacer domains. Both strains produced Chl a under white light (WL) but additionally induced Chl f synthesis under far-red light (FRL). Unexpectedly, the content of Chl f in P. sichuanica was nearly half that in most Chl f-producing cyanobacteria. Red-shifted phycobiliproteins were also induced in both strains under FRL conditions. Subsequently, additional absorption peak beyond 700 nm in the FRL spectral region appeared in these two strains. This is the first report of Chl f production induced by FRL in the family Oculatellaceae. This study not only extended the diversity of Chl f-producing cyanobacteria but also provided precious samples to elucidate the essential binding sites of Chl f within cyanobacterial photosystems.

Cadmium promotes the absorption of ammonium in hyperaccumulator Solanum nigrum L. mediated by ammonium transporters and aquaporins.

Cadmium (Cd) is a toxic heavy metal affecting the normal growth of plants. Nitrate (NO3-) and ammonium (NH4+) are the primary forms of inorganic nitrogen (N) absorbed by plants. However, the mechanism of N absorption and regulation under Cd stress remains unclear. This study found that: (1) Cd treatment affected the biomass, root length, and Cd2+ flux in Solanum nigrum seedling roots. Specifically, 50 µM Cd significantly inhibited NO3- influx while increased NH4+ influx compared with 0 and 5 µM Cd treatments measured by non-invasive micro-test technology. (2) qRT-PCR analysis showed that 50 µM Cd inhibited the expressions of nitrate transporter genes, SnNRT2;4 and SnNRT2;4-like, increased the expressions of ammonium transporter genes, SnAMT1;2 and SnAMT1;3, in the roots. (3) Under NH4+ supply, 50 µM Cd significantly induced the expressions of the aquaporin genes, SnPIP1;5, SnPIP2;7, and SnTIP2;1. Our results showed that 50 µM Cd stress promoted NH4+ absorption by up-regulating the gene expressions of NH4+ transporter and aquaporins, suggesting that high Cd stress can affect the preference of N nutrition in S. nigrum.

Exogenous hydrogen sulfide mediates Na+ and K+ fluxes of salt gland in salt-secreting mangrove plant Avicennia marina.

Hydrogen sulfide (H2S), is a crucial biological player in plants. Here, we primarily explored the interaction between sodium hydrosulfide (NaHS, a H2S donor) and the fluxes of Na+ and K+ from the salt glands of mangrove species Avicennia marina (Forsk.) Vierh. with non-invasive micro-test technology (NMT) and quantitative real-time PCR (qRT-PCR) approaches under salinity treatments. The results showed that under 400-mM NaCl treatment, the addition of 200-µM NaHS markedly increased the quantity of salt crystals in the adaxial epidermis of A. marina leaves, accompanied by an increase in the K+/Na+ ratio. Meanwhile, the endogenous content of H2S was dramatically elevated in this process. The NMT result revealed that the Na+ efflux was increased from salt glands, whereas K+ efflux was decreased with NaHS application. On the contrary, the effects of NaHS were reversed by H2S scavenger hypotaurine (HT), and DL-propargylglycine (PAG), an inhibitor of cystathionine-γ-lyase (CES, a H2S synthase). Moreover, enzymic assay revealed that NaHS increased the activities of plasma membrane and tonoplast H+-ATPase. qRT-PCR analysis revealed that NaHS significantly increased the genes transcript levels of tonoplast Na+/H+ antiporter (NHX1), plasma membrane Na+/H+ antiporter (SOS1), plasma membrane H+-ATPase (AHA1) and tonoplast H+-ATPase subunit c (VHA-c1), while suppressed above-mentioned gene expressions by the application of HT and PAG. Overall, H2S promotes Na+ secretion from the salt glands of A. marina by up-regulating the plasma membrane and tonoplast Na+/H+ antiporter and H+-ATPase.

Ammonium has stronger Cd detoxification ability than nitrate by reducing Cd influx and increasing Cd fixation in Solanum nigrum L.

Cadmium (Cd) is a harmful heavy metal that affects the growth and development of plants. Nitrogen (N) is an essential nutrient for plants, and appropriate N management can improve Cd tolerance. The aim of our study was to explore the effects of different forms of N on the molecular and physiological responses of the hyperaccumulator Solanum nigrum to Cd toxicity. Measurement of biomass, photosynthetic parameters, and Cd2+ fluxes using non-invasive micro-test technique, Cd fluorescent dying, biochemical methods and quantitative real-time PCR analysis were performed in our study. Our results showed that ammonium (NH4+) has stronger Cd detoxification ability than nitrate (NO3-), which are likely attributed to the following three reasons: (1) NH4+ decreased the influx and accumulation of Cd2+ by regulating the transcription of Cd transport-related genes; (2) the ameliorative effects of NH4+ were accompanied by the increased retention of Cd in the cell walls of roots; and (3) NH4+ up-regulated SnExp expression.

Thoracoscopic resection of a large lower esophageal schwannoma: A case report and review of the literature.

BACKGROUND: Esophageal schwannomas originating from Schwann cells are extremely rare esophageal tumors. They commonly occur in the upper and middle esophagus but less frequently in the lower esophagus. Herein, we report a rare case of a large lower esophageal schwannoma misdiagnosed as a leiomyoma. We also present a brief literature review on lower esophageal schwannomas. CASE SUMMARY: A 62-year-old man presented with severe dysphagia lasting 6 mo. A barium esophagogram showed that the lower esophagus was compressed within approximately 5.5 cm. Endoscopy revealed the presence of a large submucosal protuberant lesion in the esophagus at a distance of 32-38 cm from the incisors. Endoscopic ultrasound findings demonstrated a 4.5 cm × 5.0 cm hypoechoic lesion. Chest computed tomography revealed a mass of size approximately 53 mm × 39 mm × 50 mm. Initial tests revealed features indicative of leiomyoma. After multidisciplinary discussions, the patient underwent a video-assisted thoracoscopic partial esophagectomy. Further investigation involving immunohistochemical examination confirming palisading spindle cells as positive for S100 and Sox10 led to the final diagnosis of a lower esophageal schwannoma. There was no tumor recurrence or metastasis during follow-up. CONCLUSION: The final diagnosis of esophageal schwannoma requires histopathological and immunohistochemical examination. The early appropriate surgery favors a remarkable prognosis.

Magnesium Deficiency Triggers SGR-Mediated Chlorophyll Degradation for Magnesium Remobilization.

Magnesium (Mg) is a relatively mobile element that is remobilized in plants under Mg-limited conditions through transport from old to young tissues. However, the physiological and molecular mechanisms underlying Mg remobilization in plants remain poorly understood. In this study, we investigated Mg remobilization in rice (Oryza sativa) as facilitated through a Mg dechelatase gene involved in chlorophyll degradation, STAY-GREEN (OsSGR). We first observed that mid-aged leaves of rice are more susceptible to Mg deficiency. Expression of OsSGR was specifically upregulated by Mg deficiency, and the response was more pronounced in mid-aged leaves. Knockout of OsSGR exhibited the stay-green phenotype, which hindered the mobility of Mg from mid-aged leaves to young developing leaves. This decline in Mg mobility was associated with inhibited growth of developing leaves in mutants under Mg-limited conditions. Furthermore, Mg deficiency enhanced reactive oxygen species (ROS) generation in mid-aged leaves. ROS levels, particularly hydrogen peroxide, in turn, positively regulated OsSGR expression, probably through chloroplast-to-nucleus signaling, which triggers chlorophyll degradation to protect mid-aged leaves from photodamage. Taken together, these results show that OsSGR-mediated chlorophyll degradation contributes to not only internal remobilization of Mg from mid-aged leaves to developing leaves, but also photooxidative protection of mid-aged leaves under Mg-limited conditions. ROS appear to act as feedback regulators of OsSGR expression to precisely govern chlorophyll degradation in mid-aged leaves where Mg and photosynthetic capacities are relatively high.

Magnesium promotes root nodulation through facilitation of carbohydrate allocation in soybean.

Magnesium (Mg) is an essential element for the growth of both plants and bacteria. Low availability of Mg in agriculture can limit crop productivity and quality. In addition to direct effects on plant growth, limited Mg supply may also impact biological dinitrogen (N2 ) fixation in nodules formed from symbiotic interactions between legumes and rhizobial bacteria. To date, the physiological mechanisms involved in Mg-dependent nodulation remains largely unknown. The objectives of this work were to assess how Mg supply affects nodule growth and development in symbiotic systems, and to test if any observed changes in nodule and soybean are correlated with Mg supply. Here, we found that external Mg supply enhanced nodule growth under nitrogen (N) limited conditions, and subsequently improved N2 fixation and soybean growth. Mg supply altered neither nodule structure nor Mg homeostasis, but remarkably promoted nodule enlargement, resulting in an increase in the number of big nodules. In addition, high Mg supply decreased starch and sucrose accumulation in leaves, and increased their concentrations in roots, which consequently enhanced carbohydrate import into the rhizobia infection zone of nodules. In this study, Mg was shown to promote nodule growth in soybean. This Mg-promoted nodule growth is derived from Mg-facilitated alteration of carbohydrate partitioning and transport into nodules.

The identification of IsiA proteins binding chlorophyll d in the cyanobacterium Acaryochloris marina.

The bioavailable iron in many aquatic ecosystems is extremely low, and limits the growth and photosynthetic activity of phytoplankton. In response to iron limitation, a group of chlorophyll-binding proteins known as iron stress-induced proteins are induced and serve as accessory light-harvesting components for photosystems under iron limitation. In the present study, we investigated physiological features of Acaryochloris marina in response to iron-deficient conditions. The growth doubling time under iron-deficient conditions was prolonged to ~3.4 days compared with 1.9 days under normal culture conditions, accompanied with dramatically decreased chlorophyll content. The isolation of chlorophyll-binding protein complexes using sucrose density gradient centrifugation shows six main green bands and three main fluorescence components of 712, 728, and 748 nm from the iron-deficient culture. The fluorescence components of 712 and 728 nm co-exist in the samples collected from iron-deficient and iron-replete cultures and are attributed to Chl d-binding accessory chlorophyll-binding antenna proteins and also from photosystem II. A new chlorophyll-binding protein complex with its main fluorescence peak at 748 nm was observed and enriched in the heaviest fraction from the samples collected from the iron-deficient culture only. Combining western blotting analysis using antibodies of CP47 (PSII), PsaC (PSI) and IsiA and proteomic analysis on an excised protein band at ~37 kDa, the heaviest fraction (-F6) isolated from iron-deficient culture contained Chl d-bound PSI-IsiA supercomplexes. The PSII-antenna supercomplexes isolated from iron-replete conditions showed two fluorescence peaks of 712 and 728 nm, which can be assigned as 6-transmembrane helix chlorophyll-binding antenna and photosystem II fluorescence, respectively, which is supported by protein analysis of the fractions (F5 and F6).