Trehalose along with ABA promotes the salt tolerance of Avicennia marina by regulating Na+ transport.

Mangroves grow in tropical/subtropical intertidal habitats with extremely high salt tolerance. Trehalose and trehalose-6-phosphate (T6P) have an alleviating function against abiotic stress. However, the roles of trehalose in the salt tolerance of salt-secreting mangrove Avicennia marina is not documented. Here, we found that trehalose was significantly accumulated in A. marina under salt treatment. Furthermore, exogenous trehalose can enhance salt tolerance by promoting the Na+ efflux from leaf salt gland and root to reduce the Na+ content in root and leaf. Subsequently, eighteen trehalose-6-phosphate synthase (AmTPS) and 11 trehalose-6-phosphate phosphatase (AmTPP) genes were identified from A. marina genome. Abscisic acid (ABA) responsive elements were predicted in AmTPS and AmTPP promoters by cis-acting elements analysis. We further identified AmTPS9A, as an important positive regulator, that increased the salt tolerance of AmTPS9A-overexpressing Arabidopsis thaliana by altering the expressions of ion transport genes and mediating Na+ efflux from the roots of transgenic A. thaliana under NaCl treatments. In addition, we also found that ABA could promote the accumulation of trehalose, and the application of exogenous trehalose significantly promoted the biosynthesis of ABA in both roots and leaves of A. marina. Ultimately, we confirmed that AmABF2 directly binds to the AmTPS9A promoter in vitro and in vivo. Taken together, we speculated that there was a positive feedback loop between trehalose and ABA in regulating the salt tolerance of A. marina. These findings provide new understanding to the salt tolerance of A. marina in adapting to high saline environment at trehalose and ABA aspects.

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.

Aberrant splicing of CaV1.2 calcium channel induced by decreased Rbfox1 enhances arterial constriction during diabetic hyperglycemia.

Diabetic hyperglycemia induces dysfunctions of arterial smooth muscle, leading to diabetic vascular complications. The CaV1.2 calcium channel is one primary pathway for Ca2+ influx, which initiates vasoconstriction. However, the long-term regulation mechanism(s) for vascular CaV1.2 functions under hyperglycemic condition remains unknown. Here, Sprague-Dawley rats fed with high-fat diet in combination with low dose streptozotocin and Goto-Kakizaki (GK) rats were used as diabetic models. Isolated mesenteric arteries (MAs) and vascular smooth muscle cells (VSMCs) from rat models were used to assess K+-induced arterial constriction and CaV1.2 channel functions using vascular myograph and whole-cell patch clamp, respectively. K+-induced vasoconstriction is persistently enhanced in the MAs from diabetic rats, and CaV1.2 alternative spliced exon 9* is increased, while exon 33 is decreased in rat diabetic arteries. Furthermore, CaV1.2 channels exhibit hyperpolarized current-voltage and activation curve in VSMCs from diabetic rats, which facilitates the channel function. Unexpectedly, the application of glycated serum (GS), mimicking advanced glycation end-products (AGEs), but not glucose, downregulates the expression of the splicing factor Rbfox1 in VSMCs. Moreover, GS application or Rbfox1 knockdown dynamically regulates alternative exons 9* and 33, leading to facilitated functions of CaV1.2 channels in VSMCs and MAs. Notably, GS increases K+-induced intracellular calcium concentration of VSMCs and the vasoconstriction of MAs. These results reveal that AGEs, not glucose, long-termly regulates CaV1.2 alternative splicing events by decreasing Rbfox1 expression, thereby enhancing channel functions and increasing vasoconstriction under diabetic hyperglycemia. This study identifies the specific molecular mechanism for enhanced vasoconstriction under hyperglycemia, providing a potential target for managing diabetic vascular complications.

Genome-wide identification of Avicennia marina aquaporins reveals their role in adaptation to intertidal habitats and their relevance to salt secretion and vivipary.

Aquaporins (AQPs) regulate the transport of water and other substrates, aiding plants in adapting to stressful environments. However, the knowledge of AQPs in salt-secreting and viviparous Avicennia marina is limited. In this study, 46 AmAQPs were identified in A. marina genome, and their subcellular localisation and function in transporting H2 O2 and boron were assessed through bioinformatics analysis and yeast transformation. Through analysing their expression patterns via RNAseq and real-time quantitative polymerase chain reaction, we found that most AmAQPs were downregulated in response to salt and tidal flooding. AmPIP (1;1, 1;7, 2;8, 2;9) and AmTIP (1;5, 1;6) as salt-tolerant candidate genes may contribute to salt secretion together with Na+ /H+ antiporters. AmPIP2;1 and AmTIP1;5 were upregulated during tidal flooding and may be regulated by anaerobic-responsive element and ethylene-responsive element cis-elements, aiding in adaptation to tidal inundation. Additionally, we found that the loss of the seed desiccation and dormancy-related TIP3 gene, and the loss of the seed dormancy regulator DOG1 gene, or DOG1 protein lack heme-binding capacity, may be genetic factors contributing to vivipary. Our findings shed light on the role of AQPs in A. marina adaptation to intertidal environments and their relevance to salt secretion and vivipary.

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.

[Review of joint attention deficit intervention based on virtual reality for children with autism].

Joint attention deficit is one of the core disorders in children with autism, which seriously affects the development of multiple basic skills such as language and communication. Virtual reality scene intervention has great potential in improving joint attention skills in children with autism due to its good interactivity and immersion. This article reviewed the application of virtual reality based social and nonsocial scenarios in training joint attention skills for children with autism in recent years, summarized the problems and challenges of this intervention method, and proposed a new joint paradigm for social scenario assessment and nonsocial scenario training. Finally, it looked forward to the future development and application prospects of virtual reality technology in joint attention skill training for children with autism.

Anisotropic Hollow Structure with Chemotaxis Enabling Intratumoral Autonomic Therapy.

Effective intratumoral drug penetration is pivotal for successful cancer treatment. However, due to the disrupted capillary networks and poor perfusion in solid tumors, there exist challenges to realize autonomous directional drug penetration and controlled drug release within the tumor. Considering the specificity of glucose within tumor tissue, we draw inspiration from nature and engineer asymmetrical hollow structures exhibiting chemotaxis towards high glucose levels. By incorporating multiple shells into these structures, we enhance the local chemical concentration gradients, thereby improving cellular uptake and precise targeting. The advantages of anisotropic hollow multishell structure (a-HoMS) can be reflected from the diffusion coefficient and directivity, which increase by 73.4% and 265% respectively compared to conventional isotropic hollow spheres, achieving the most linear movement while ensuring the speed of movement. Furthermore, the multi-level porosity and temporal-spatial order of a-HoMS enable sequential drug delivery that inhibits angiogenesis with inducing cell apoptosis. After the eradication of localized tumor cells, the a-HoMS can automatically migrate to the alive tumor cells under the glucose gradient, inducing another cycle of drug delivery and chemotaxis, resulting in excellent antitumor efficacy. These anisotropic HoMS demonstrate intelligence, adaptability, and precision in tumor therapy, providing valuable insights for programmable treatment within tissues.

In silico analysis of NAC gene family in the mangrove plant Avicennia marina provides clues for adaptation to intertidal habitats.

NAC (NAM, ATAF1/2, CUC2) transcription factors (TFs) constitute a plant-specific gene family. It is reported that NAC TFs play important roles in plant growth and developmental processes and in response to biotic/abiotic stresses. Nevertheless, little information is known about the functional and evolutionary characteristics of NAC TFs in mangrove plants, a group of species adapting coastal intertidal habitats. Thus, we conducted a comprehensive investigation for NAC TFs in Avicennia marina, one pioneer species of mangrove plants. We totally identified 142 NAC TFs from the genome of A. marina. Combined with NAC proteins having been functionally characterized in other organisms, we built a phylogenetic tree to infer the function of NAC TFs in A. marina. Gene structure and motif sequence analyses suggest the sequence conservation and transcription regulatory regions-mediated functional diversity. Whole-genome duplication serves as the driver force to the evolution of NAC gene family. Moreover, two pairs of NAC genes were identified as positively selected genes of which AmNAC010/040 may be imposed on less constraint toward neofunctionalization. Quite a few stress/hormone-related responsive elements were found in promoter regions indicating potential response to various external factors. Transcriptome data revealed some NAC TFs were involved in pneumatophore and leaf salt gland development and response to salt, flooding and Cd stresses. Gene co-expression analysis found a few NAC TFs participates in the special biological processes concerned with adaptation to intertidal environment. In summary, this study provides detailed functional and evolutionary information about NAC gene family in mangrove plant A. marina and new perspective for adaptation to intertidal habitats.

Structure and Conductivity in LISICON Analogues within the Li4GeO4-Li2MoO4 System.

New solid electrolytes are crucial for the development of all-solid-state lithium batteries with advantages in safety and energy densities over current liquid electrolyte systems. While some of the best solid-state Li+-ion conductors are based on sulfides, their air sensitivity makes them less commercially attractive, and attention is refocusing on air-stable oxide-based systems. Among these, the LISICON-structured systems, such as Li2+2xZn1-xGeO4 and Li3+xV1-xGexO4, have been relatively well studied. However, other systems such as the Li4GeO4-Li2MoO4 system, which also show LISICON-type structures, have been relatively little explored. In this work, the Li4-2xGe1-xMoxO4 solid solution is investigated systematically, including the solid solution limit, structural stability, local structure, and the corresponding electrical behavior. It is found that a γ-LISICON structured solution is formed in the range of 0.1 ≤ x < 0.4, differing in structure from the two end members, Li4GeO4 and Li2MoO4. With increasing Mo content, the ß-phase becomes increasingly more stable than the γ-phase, and at x = 0.5, a pure ß-phase (ß-Li3Ge0.5Mo0.5O4) is readily isolated. The structure of this previously unknown compound is presented, along with details of the defect structure of Li3.6Ge0.8Mo0.2O4 (x = 0.2) based on neutron diffraction data. Two basic types of defects are identified in Li3.6Ge0.8Mo0.2O4 involving interstitial Li+-ions in octahedral sites, with evidence for these coming together to form larger defect clusters. The x = 0.2 composition shows the highest conductivity of the series, with values of 1.11 × 10-7 S cm-1 at room temperature rising to 5.02 × 10-3 S cm-1 at 250 °C.

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.

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.

Association Strategies of Speech Behavior of Communicators in Coding Discourse: An Interdisciplinary Approach Towards Understanding the Role of Cognitive and Linguistic Processes in Communication.

In modern media, the names of fairy-tale and mythological images are used to convey certain emotions and connotations. The aim of the study is to analyze the characteristic associative strategies presented with the mythological images of a dragon, a paper tiger and a chimera in news texts of European and Chinese mass media. In this article, the method of text analysis was used to identify patterns and the most possible interpretations of lexical units. 100 articles from Chinese and European publications were selected for the analysis (About People's Daily Online, China News Service, Guardian and France 24). The required lexemes were most widely used in articles on political topics. The most used was the image of a paper tiger (4001 and 3587 units). This is due to its well-known metaphorical meaning in both cultures, while dragon differs in Chinese and European ones. Further research may focus on the search and analysis of other fairy tale and mythological images in mass media. The present study results may also be applied for further research in the field of linguistics and journalism.

[Effect evaluation of graphical menu labeling in simulated ordering].

OBJECTIVE: To explore the feasibility of applying graphical menu labeling. METHODS: To design a radar chart menu label. From October 2020 to April 2021, convenience sampling was adopted to recruit 1407 research subjects(986 females and 421 males) through the online platform nationwide to complete the questionnaire and simulate ordering. The survey included basic information of the research subjects, their level of nutritional knowledge, and satisfaction with the graphic menu labels. The two simulated orderings were conducted using the regular menu and the menu with graphic nutritional information, respectively. Compare the nutrition scores of the two simulated orders, the selection ratio of each dish in each major category, the energy, fat, cholesterol and sodium content, and the amount of added oil and salt of the selected dishes. RESULTS: Compared with using the normal menu, the nutritional score of the simulated meal ordering increased from 15.57±2.65 to 16.73±3.24(P<0.05) using a menu with graphic nutrition labels, in which people with an income of less than 4000 yuan and a graduate degree or above increased the most. The proportion of dishes with higher nutritional value has increased among pork, fish, vegetables, and soy products. The energy, fat, cholesterol, sodium content, added oil and added salt of the selected dishes are decreased from 8455(7738, 9033) kcal, 658.6(598.1, 709.3) g, 1418(1238, 1665) mg, 17 430(15 695, 19 129)mg, 455(405, 502)g, 41.5(36.5, 47.0)g to 7415(6693, 8191)kcal, 562.54(504.0, 631.2)g, 1274(1076, 1549)mg, 17 185(14 574, 19 576.8)mg, 375(334, 437) g, 38.5(32.4, 43.6) g respectively(P<0.05). The satisfaction score of the graphic nutrition label is relatively high. CONCLUSION: Graphical menu labeling helps consumers to make healthier choices for catering food.

[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.

Genome-wide identification and characterization of aquaporins in mangrove plant Kandelia obovata and its role in response to the intertidal environment.

Aquaporins (AQPs) play important roles in plant growth, development and tolerance to environmental stresses. To understand the role of AQPs in the mangrove plant Kandelia obovata, which has the ability to acquire water from seawater, we identified 34 AQPs in the K. obovata genome and analysed their structural features. Phylogenetic analysis revealed that KoAQPs are homologous to AQPs of Populus and Arabidopsis, which are evolutionarily conserved. The key amino acid residues were used to assess water-transport ability. Analysis of cis-acting elements in the promoters indicated that KoAQPs may be stress- and hormone-responsive. Subcellular localization of KoAQPs in yeast showed most KoAQPs function in the membrane system. That transgenic yeast with increased cell volume showed that some KoAQPs have significant water-transport activity, and the substrate sensitivity assay indicates that some KoAQPs can transport H2 O2 . The transcriptome data were used to analyze the expression patterns of KoAQPs in different tissues and developing fruits of K. obovata. In addition, real-time quantitative PCR analyses combined transcriptome data showed that KoAQPs have complex responses to environmental factors, including salinity, flooding and cold. Collectively, the transport of water and solutes by KoAQPs contributed to the adaptation of K. obovata to the coastal intertidal environment.

Genome-Wide Identification of Long Noncoding RNA and Their Potential Interactors in ISWI Mutants.

Long non-coding RNAs (lncRNAs) have been identified as key regulators of gene expression and participate in many vital physiological processes. Chromatin remodeling, being an important epigenetic modification, has been identified in many biological activities as well. However, the regulatory mechanism of lncRNA in chromatin remodeling remains unclear. In order to characterize the genome-wide lncRNA expression and their potential interacting factors during this process in Drosophila, we investigated the expression pattern of lncRNAs and mRNAs based on the transcriptome analyses and found significant differences between lncRNAs and mRNAs. Then, we performed TSA-FISH experiments of candidate lncRNAs and their potential interactors that have different functions in Drosophila embryos to determine their expression pattern. In addition, we also analyzed the expression of transposable elements (TEs) and their interactors to explore their expression in ISWI mutants. Our results provide a new perspective for understanding the possible regulatory mechanism of lncRNAs and TEs as well as their targets in chromatin remodeling.

[Distribution and bioactivity of polyphenols in Opuntia ficus-indica (L. ) Mill].

OBJECTIVE: To study the distribution of the polyphenols of Opuntia ficus-indica(L. ) Mill, and study its antioxidant and the inhibition of sugar digestive enzyme activities by vitro experiments. METHODS: Using ethanol as solvent, free polyphenols, esterified polyphenols, and insoluble bonded polyphenols were extracted from the peel, pulp and seeds of Opuntia ficus-indica(L. ) Mill, and their contents were determined by the Folin-Ciocalteu method. Antioxidant activity was measured according to their ability to scavenge DPPH, OH and ABTS~(+ )radicals, and the inhibition of α-glucosidase and α-amylase activities by various types of polyphenols in various parts was observed in vitro. RESULTS: The peel polyphenol content of Opuntia ficus-indica(L. ) Mill was(1427.15±34.48) mg GAE/100 g, the pulp polyphenol content was(525.88±51.66) mg GAE/100 g, and the seed polyphenol content was(256.92±3.81) mg GAE/100 g. The free polyphenols, esterified polyphenols, and insoluble bonded polyphenols of different parts of Opuntia ficus-indica(L. ) Mill have the ability to scavenge DPPH, OH and ABTS~(+ )radicals, and the seeds had the strongest antioxidant capacity among all parts, the esterified polyphenols and insoluble bonded polyphenols of pulp and seeds of Opuntia ficus-indica(L. ) Mill have inhibitory effects on the activities of α-glucosidase and α-amylase, with seed polyphenols have the strongest inhibitory ability. CONCLUSION: Opuntia ficus-indica(L. ) Mill has the highest content of polyphenols in the peel, and seed polyphenols have good antioxidant and the inhibition of sugar digestive enzyme activities.

OsMGT1 Confers Resistance to Magnesium Deficiency By Enhancing the Import of Mg in Rice.

Magnesium (Mg) is an essential nutrient element for plant growth and plays an important role in numerous physiological and biochemical processes. Mg deficiency inhibits plant growth and has become a growing problem for crop productions in agriculture. However, the molecular mechanisms for the resistance to Mg deficiency in plants were not well understood. In this study, we identified a Mg transporter gene OsMGT1 that confers resistance to Mg deficiency in rice (Oryza sativa). The expression of OsMGT1 was highly induced by Mg deficiency in shoots. Investigation of tissue expression patterns revealed that OsMGT1 was mainly expressed in the phloem region; however, Mg deficiency remarkably enhanced its expression in xylem parenchyma and mesophyll cells in shoots. Knockout of OsMGT1 resulted in a significant reduction in Mg content and biomass when grown at Mg-limited conditions. Furthermore, the sensitivity to low-Mg in mutants was intensified by excessive calcium supply. In addition, overexpression of OsMGT1 increased Mg content and biomass under low-Mg supply. In conclusion, our results indicate that OsMGT1 plays an important role in rice Mg import and is required for the resistance to Mg deficiency, which can be utilized for molecular breeding of low-Mg tolerant plants.

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).

Riemerella anatipestifer extracellular protease S blocks complement activation via the classical and lectin pathways.

Riemerella anatipestifer (RA) is the causative agent of infectious serositis in ducklings and other avian species. It is difficult to control the disease due to its 21 serotypes, poor cross-protection, and bacterial resistance to antimicrobial agents. The complement system is an important component of the innate immune system. However, bacterial pathogens exploit several strategies to evade detection by the complement system. Here, we purified and identified a 59-kDa RA extracellular protease S (EcpS) consisting of a gelatinase. In this study, we aimed to determine how EcpS interferes with complement activation and whether it could block complement-dependent neutrophil function. We found that EcpS potently blocked RA phagocytosis and killing by duck neutrophils. Furthermore, EcpS inhibited the opsonization of bacteria by complement 3b. EcpS specifically blocked complement 3b and complement 4b deposition via the classical and lectin pathways, whereas the alternative pathway was not affected. In summary, we show that RA can survive the bactericidal activity of the duck complement system. These results indicate that RA has evolved mechanisms to evade the duck complement system that may increase the efficiency by which this pathogen can gain access and colonize the inner tissues where it may cause severe infections.