The chromosome-level genome assembly of Cananga odorata provides insights into its evolution and terpenoid biosynthesis.

Cananga odorata is known as a natural perfume tree of the Annonaceae family in Magnoliales. However, its phylogenetic position and the molecular mechanisms involved in the biosynthesis of the floral volatile organic compounds (VOCs) remain unclear. Here, by combining a variety of sequencing platforms, we present a telomere-to-telomere (T2T) genome of C. odorata with 735.83 Mb, which represents the highest integrity and assembly quality of genome in magnoliid plants reported to date. Phylogenetic analysis based on multiple datasets and approaches showed that C. odorata, as a member of magnoliids, is sister to eudicots, after their divergence from monocots. Metabolomic of VOCs in the essential oil and flowers scent showed that sesquiterpenes, especially ß-caryophyllene, were the major compounds. Two CoTPS21 homologues derived from tandem duplication events were highly expressed during flower development and were identified as the key sesquiterpene synthases for the production of ß-caryophyllene. In addition, CoSPL3 and CoSPL9 were considered as potential transcription factors for activating the expression of CoTPS21 homologues. Our results shed light on the molecular mechanisms underlying the biosynthesis of the unique floral fragrance in C. odorata and provide new insights into the phylogenetic position of magnoliids.

Cyclic peptide conjugated photosensitizer for targeted phototheranostics of gram-negative bacterial infection.

Antimicrobial photodynamic therapy (PDT) is a promising alternative to antibiotics for eradicating pathogenic bacterial infections. It holds advantage of not inducing antimicrobial resistance but is limited for the treatment of gram-negative bacterial infection due to the lack of photosensitizer (PS) capable of targeted permeating the outer membrane (OM) of gram-negative bacteria. To facilitate the targeted permeability of PS, cyclic polymyxin b nonapeptide that can specifically bind to the lipopolysaccharide on OM, is conjugated to an FDA approved PS chlorin e6 via variable linkers. Based on structure to activity study, C6pCe6 with aminohexanoic linker and P2pCe6 with amino-3, 6-dioxaoctanoic linker are identified to preferentially image gram-negative bacteria. These two conjugates also exhibit improved aqueous dispersity and enhanced ROS generation, consequently enabled their selective bactericidal activities against gram-negative bacteria upon 660 nm light irradiation. The effective photobactericidal ability of P2pCe6 is further validated on P. aeruginosa infected G. mellonella. Moreover, it is demonstrated to effectively treat the P. aeruginosa infection and accelerate the healing process at the wound site of mouse. Owing to the light irradiation triggered targeted imaging and enhanced bactericidal capacities, P2pCe6 hold great potential to serve as a potent PS for mediating the phototheranostics of gram-negative bacterial infection.

The evolution and functional divergence of FT-related genes in controlling flowering time in Brassica rapa ssp. rapa.

KEY MESSAGE: The BrrFT paralogues exhibit distinct expression patterns and play different roles in regulating flowering time, and BrrFT4 competes with BrrFT1 and BrrFT2 to interact with BrrFD proteins. Flowering time is an important agricultural trait for Brassica crops, and early bolting strongly affects the yield and quality of Brassica rapa ssp. rapa. Flowering Locus T paralogues play an important role in regulating flowering time. In this study, we identified FT-related genes in turnip by phylogenetic classification, and four BrrFT homoeologs that shared with high identities with BraFT genes were isolated. The different gene structures, promoter binding sites, and expression patterns observed indicated that these genes may play different roles in flowering time regulation. Further genetic and biochemical experiments showed that as for FT-like paralogues, BrrFT2 acted as the key floral inducer, and BrrFT1 seems to act as a mild 'florigen' protein. However, BrrFT4 acts as a floral repressor and antagonistically regulates flowering time by competing with BrrFT1 and BrrFT2 to bind BrrFD proteins. BrrFT3 may have experienced loss of function via base shift mutation. Our results revealed the potential roles of FT-related genes in flowering time regulation in turnip.

Rapid Nucleic Acid Detection of Listeria monocytogenes Based on RAA-CRISPR Cas12a System.

Listeria monocytogenes (L. monocytogenes) is a food-borne pathogenic bacteria that frequently contaminates animal-derived food and low-temperature preserved food. Listeriosis caused by its infection has a high mortality rate and poses a serious threat to human health. Therefore, it is crucial to establish a sensitive, rapid and easy-to-operate technique. In this study, a Recombinase Aided Amplification (RAA) assisted CRISPR/Cas12a (RAA-CRISPR/Cas12a) fluorescence platform was established for highly sensitive nucleic acid detection of L. monocytogenes. The established RAA-CRISPR/Cas12a showed high sensitivity and high specificity, with the sensitivity of 350 CFU/mL and 5.4 × 10-3 ng/µL for pure bacterial solution and genomic DNA, and good specificity for 5 strains of Listeria spp. and 14 strains of other common pathogenic bacteria. L. monocytogenes could be detected at an initial concentration of 2.3 CFU/25g within 2 h of enriching the beef in the food matrix, and this method could be applied to food samples that were easily contaminated with L. monocytogenes The results of RAA-CRISPR/Cas12a could be observed in 5 min, while the amplification was completed in 20-30 min. The speed and sensitivity of RAA-CRISPR/Cas12a were significantly higher than that of the national standard method. In conclusion, the RAA-CRISPR/Cas12a system established in this study has new application potential in the diagnosis of food-borne pathogens.

Effects of Flavourzyme and Alkaline Protease Treatment on Structure and Allergenicity of Peanut Allergen Ara h 1.

Research background: Peanut allergy poses a significant threat to human health due to the increased risk of long-term morbidity at low doses. Modifying protein structure to affect sensitization is a popular topic. Experimental approach: In this study, the purified peanut allergen Ara h 1 was enzymatically hydrolysed using Flavourzyme, alkaline protease or a combination of both. The binding ability of Ara h 1 to antibodies, gene expression and secretion levels of the proinflammatory factors interleukin-5 and interleukin-6 in Caco-2 cells was measured. Changes in the secondary and tertiary structures before and after treatment with Ara h 1 were analysed by circular dichroism and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Results and conclusions: The results indicated a decrease of the allergenicity and proinflammatory ability of Ara h 1. The evaluation showed that the Flavourzyme and alkaline protease treatments caused particle shortening and aggregation. The fluorescence emission peak increased by 3.4-fold after the combined treatment with both proteases. Additionally, the secondary structure underwent changes and the hydrophobicity also increased 8.95-fold after the combined treatment. Novelty and scientific contribution: These findings partially uncover the mechanism of peanut sensitization and provide an effective theoretical basis for the development of a new method of peanut desensitization.

ICE1 interacts with IDD14 to transcriptionally activate QQS to increase pollen germination and viability.

In flowering plants, sexual reproductive success depends on the production of viable pollen grains. However, the mechanisms by which QUA QUINE STARCH (QQS) regulates pollen development and how transcriptional activators facilitate the transcription of QQS in this process remain poorly understood. Here, we demonstrate that INDUCER OF CBF EXPRESSION 1 (ICE1), a basic helix-loop-helix (bHLH) transcription factor, acts as a key transcriptional activator and positively regulates QQS expression to increase pollen germination and viability in Arabidopsis thaliana by interacting with INDETERMINATE DOMAIN14 (IDD14). In our genetic and biochemical experiments, overexpression of ICE1 greatly promoted both the activation of QQS and high pollen viability mediated by QQS. IDD14 additively enhanced ICE1 function by promoting the binding of ICE1 to the QQS promoter. In addition, mutation of ICE1 significantly repressed QQS expression; the impaired function of QQS and the abnormal anther dehiscence jointly affected pollen development of the ice1-2 mutant. Our results also showed that the enhancement of pollen activity by ICE1 depends on QQS. Furthermore, QQS interacted with CUT1, the key enzyme for long-chain lipid biosynthesis. This interaction both promoted CUT1 activity and regulated pollen lipid metabolism, ultimately determining pollen hydration and fertility. Our results not only provide new insights into the key function of QQS in promoting pollen development by regulating pollen lipid metabolism, but also elucidate the mechanism that facilitates the transcription of QQS in this vital developmental process.

Overlapping Physiologic Signs of Sepsis and Paroxysmal Sympathetic Hyperactivity After Traumatic Brain Injury: Exploring A Clinical Conundrum.

BACKGROUND: Paroxysmal sympathetic hyperactivity (PSH) occurs in a subset of patients with traumatic brain injury (TBI) and is associated with worse outcomes. Sepsis is also associated with worse outcomes after TBI and shares several physiologic features with PSH, potentially creating diagnostic confusion and suboptimal management of each. This is the first study to directly investigate the interaction between PSH and infection using robust diagnostic criteria. METHODS: We performed a retrospective cohort study of patients with TBI admitted to a level I trauma center intensive care unit with hospital length of stay of at least 2 weeks. From January 2016 to July 2018, 77 patients diagnosed with PSH were 1:1 matched by age and Glasgow Coma Scale to 77 patients without PSH. Trauma infectious diseases subspecialists prospectively documented assessments corroborating diagnoses of infection. Extracted data including incidence, timing, classification, and anatomical source of infections were compared according to PSH diagnosis. We also evaluated daily PSH clinical feature severity scores and systemic inflammatory response syndrome (SIRS) criteria and compared values for patients with and without confirmed infection, stratified by PSH diagnosis. RESULTS: During the first 2 weeks of hospitalization, there were no differences in rates of suspected (62%) nor confirmed (48%) infection between patients with PSH and controls. Specific treatments for PSH were initiated on median hospital day 7 and for confirmed infections on median hospital day 8. SIRS criteria could identify infection only in patients who were not diagnosed with PSH. CONCLUSIONS: In the presence of brain injury-induced autonomic nervous system dysregulation, the initiation and continuation of antimicrobial therapy is a challenging clinical decision, as standard physiologic markers of sepsis do not distinguish infected from noninfected patients with PSH, and these entities often present around the same time. Clinicians should be aware that PSH is a potential driver of SIRS, and familiarity with its diagnostic criteria as proposed by the PSH assessment measure is important. Management by a multidisciplinary team attentive to these issues may reduce rates of inappropriate antibiotic usage and misdiagnoses.

Cold Response Transcriptome Analysis of the Alternative Splicing Events Induced by the Cold Stress in D. catenatum.

Dendrobium catenatum Lindl is a valuable medicinal herb and gardening plant due to its ornamental value and special medical value. Low temperature is a major bottleneck restricting D. catenatum expansion towards the north, which influences the quality and yield of D. catenatum. In this study, we analysed the cold response of D. catenatum by RNA-Seq. A total of 4302 differentially expressed genes were detected under cold stress, which were mainly linked to protein kinase activity, membrane transport and the glycan biosynthesis and metabolism pathway. We also identified 4005 differential alternative events in 2319 genes significantly regulated by cold stress. Exon skipping and intron retention were the most common alternative splicing isoforms. Numerous genes were identified that differentially modulated under cold stress, including cold-induced transcription factors and splicing factors mediated by AS (alternative splicing). GO enrichment analysis found that differentially alternatively spliced genes without differential expression levels were related to RNA/mRNA processing and spliceosomes. DAS (differentially alternative splicing) genes with different expression levels were mainly enriched in protein kinase activity, plasma membrane and cellular response to stimulus. We further identified and cloned DcCBP20 in D. catenatum; we found that DcCBP20 promotes the generation of alternative splicing variants in cold-induced genes under cold stress via genetic experiments and RT-PCR. Taken together, our results identify the main cold-response pathways and alternative splicing events in D. catenatum responding to cold treatment and that DcCBP20 of D. catenatum get involved in regulating the AS and gene expression of cold-induced genes during this process. Our study will contribute to understanding the role of AS genes in regulating the cold stress response in D. catenatum.

Comparative transcriptome analysis reveals ecological adaption of cold tolerance in northward invasion of Alternanthera philoxeroides.

BACKGROUND: Alternanthera philoxeroides (alligator weed) is a highly invasive alien plant that has continuously and successfully expanded from the tropical to the temperate regions of China via asexual reproduction. During this process, the continuous decrease in temperature has been a key limiting environmental factor. RESULTS: In this study, we provide a comprehensive analysis of the cold tolerance of alligator weed via transcriptomics. The transcriptomic differences between the southernmost population and the northernmost population of China were compared at different time points of cold treatments. GO enrichment and KEGG pathway analyses showed that the alligator weed transcriptional response to cold stress is associated with genes encoding protein kinases, transcription factors, plant-pathogen interactions, plant hormone signal transduction and metabolic processes. Although members of the same gene family were often expressed in both populations, the levels of gene expression between them varied. Further ChIP experiments indicated that histone epigenetic modification changes at the candidate transcription factor gene loci are accompanied by differences in gene expression in response to cold, without variation in the coding sequences of these genes in these two populations. These results suggest that histone changes may contribute to the cold-responsive gene expression divergence between these two populations to provide the most beneficial response to chilling stimuli. CONCLUSION: We demonstrated that the major alterations in gene expression levels belonging to the main cold-resistance response processes may be responsible for the divergence in the cold resistance of these two populations. During this process, histone modifications in cold-responsive genes have the potential to drive the major alterations in cold adaption necessary for the northward expansion of alligator weed.

Expression of FRIGIDA in root inhibits flowering in Arabidopsis thaliana.

FRIGIDA (FRI), as the major regulator of flowering time in Arabidopsis accessions, can activate its target FLOWERING LOCUS C (FLC) to delay flowering before vernalization. In addition to FLC, other FRI targets also exist in Arabidopsis. Although leaves sense environmental cues to modulate flowering time, it is not known if roots also regulate the floral transition. In this study, we investigated the spatio-temporal effect of FRI on flowering time. Local expression of FRI in the phloem and leaves activated FLC to delay flowering. Furthermore, we found that local expression of FRI in the roots also delayed flowering by activating other targets, MADS AFFECTING FLOWERING4 (MAF4) and MAF5, in the roots. Graft and genetic experiments revealed that the spatial expression of FRI in the root might generate a mobile signal, which is transmitted from roots to shoot and antagonizes the FT signal to delay flowering. Specifically expressing FRI in the embryo efficiently delayed flowering, even expressing FRI as early as the pro-embryo stage is enough to up-regulate FLC expression to delay flowering. Together, our findings demonstrate the spatio-temporal effect of FRI on delaying flowering, and we propose that root tissue also perceives the flowering signal to fine-tune the flowering time through MAF4/5 as novel targets of FRI.

Functional FRIGIDA allele enhances drought tolerance by regulating the P5CS1 pathway in Arabidopsis thaliana.

Flowering at the right time is important for the reproductive success of plants and their response to environmental stress. In Arabidopsis, a major determinant of natural variation in flowering time is FRIGIDA (FRI). In the present study, we show that overexpression of the functional FRIGIDA gene in wild-type Col background (ColFRI) positively enhances the drought tolerance by activating P5CS1 expression and promoting proline accumulation during water stress. Furthermore, no significant changes in FRI gene and protein expression levels were observed with drought treatment, whereas P5CS1 protein expression significantly increased. In contrast, vernalization treatment efficiently reduced P5CS1 expression levels and resulted in a decrease in drought tolerance in the ColFRI plants. The flc mutants with a functional FRI background also relieved FRI-mediated activation of P5CS1 during drought tolerance. Taken together, our findings reveal the novel function of FRI in enhancing drought resistance through its downstream P5CS1 pathway during water-deficit stress, which is dependent on its target, the FLC gene.

AFP2 as the novel regulator breaks high-temperature-induced seeds secondary dormancy through ABI5 and SOM in Arabidopsis thaliana.

Imbibed seeds monitor environmental and endogenous signals to break dormancy and initiate growth under appropriate conditions. In Arabidopsis thaliana, high temperature (HT) induces secondary seed dormancy, but the underlying mechanism remains unclear. In this study, we found that the abi5-1 mutant was insensitive to high temperature, whereas plants overexpressing ABI5 displayed sensitivity. We then identified ABA-insensitive five-binding protein 2 (AFP2), which interacts with ABI5 and is involved in HT-induced secondary seed dormancy. Under HT stress, the loss-of-function afp2 mutant showed lower seeds germination frequency, reversely, AFP2 overexpressing lines (OE-AFP2) showed high germination frequency. Similar to the abi5 mutant, the crossed OE-AFP2 abi5 or afp2 abi5 lines showed high germination under HT, suggesting that ABI5 is epistatic to AFP2. SOM is reported to negatively regulate seeds germination by altering GA/ABA metabolism, here we found that AFP2 and ABI5 altered SOM transcription. Specifically, overexpressing AFP2 suppressed SOM transcription, resulting in high expression of GA biosynthesis-related genes and low expression of ABA biosynthesis-related genes, ultimately promoting seed germination under HT. Thus, our data demonstrate that AFP2 is a novel regulator to control HT-induced secondary seed dormancy through ABI5 and SOM.

The glutamate receptors AtGLR1.2 and AtGLR1.3 increase cold tolerance by regulating jasmonate signaling in Arabidopsis thaliana.

Plant glutamate-like receptors (GLRs), which are homologs of mammalian ionotropic glutamate receptors (iGluRs), are thought to be involved in plant growth, development, and environmental stress responses. In this study, we demonstrated that two members of Arabidopsis glutamate-like receptors, AtGLR1.2 and AtGLR1.3, play positive roles in the plant response to cold stress. Genetic and biochemical experiments revealed that exogenous jasmonate could attenuate the cold sensitivity of glr1.2 and glr1.3 mutants, and the overexpression of GLR1.2 or GLR1.3 enhanced cold tolerance by increasing endogenous jasmonate levels under cold stress. In addition, the expression of genes in the CBF/DREB1 signaling pathway was decreased in the glr1.2 and glr1.3 mutants, but was promoted in GLR1.2-OE and GLR1.3-OE transgenic plants compared with the wild-type during cold treatment. Further investigation revealed that AtGLR1.2 and AtGLR1.3 independently drove similar functions without directly interacting. Together, our findings suggest that AtGLR1.2 and 1.3 positively enhance cold tolerance in Arabidopsis by activating endogenous jasmonate accumulation and subsequently promoting the downstream CBF/DREB1 cold response pathway during cold stress.

Proteasome-mediated degradation of FRIGIDA modulates flowering time in Arabidopsis during vernalization.

Winter-annual accessions of Arabidopsis thaliana require either exposure to cold stress or vernalization to initiate flowering via FRIGIDA (FRI). FRI acts as a scaffold protein to recruit several chromatin modifiers that epigenetically modify flowering genes. Here, we report that proteasome-mediated FRI degradation regulates flowering during vernalization in Arabidopsis. Our genetic and biochemical experiments demonstrate that FRI directly interacts with the BTB (Bric-a-Brac/Tramtrack/Broad Complex) proteins LIGHT-RESPONSE BTB1 (LRB1) and LRB2 as well as the CULLIN3A (CUL3A) ubiquitin-E3 ligase in vitro and in vivo, leading to proteasomal degradation of FRI during vernalization. The degradation of FRI is accompanied by an increase in the levels of the long noncoding RNA ColdAIR, which reduces the level of histone H3Lys4 trimethylation (H3K4me3) in FLOWERING LOCUS C chromatin to promote flowering. Furthermore, we found that the cold-induced WRKY34 transcription factor binds to the W-box in the promoter region of CUL3A to modulate CUL3A expression. Deficiency of WRKY34 suppressed CUL3A transcription to enhance FRI protein stability and led to late flowering after vernalization. Conversely, overexpression of WRK34 promoted FRI degradation and early flowering through inducing CUL3A accumulation. Together, these data suggest that WRKY34-induced and CUL3A-dependent proteolysis of FRI modulate flowering in response to vernalization.

The role of nitric oxide signalling in response to salt stress in Chlamydomonas reinhardtii.

MAIN CONCLUSION: Nitric oxide signal and GSNOR activity play an essential role for Chlamydomonas reinhardtii response to salt stress. The unicellular alga Chlamydomonas reinhardtii is one of the most important model organisms phylogenetically situated between higher plants and animals. In the present study, we used comparative proteomics and physiological approaches to study the mechanisms underlying the response to salt stress in C. reinhardtii. We identified 74 proteins that accumulated differentially after salt stress, including oxidative enzymes and enzymes associated with nitric oxide (NO) metabolism, cell damage, and cell autophagy processes. A set of antioxidant enzymes, as well as S-nitrosoglutathione reductase (GSNOR) activity, were induced to balance the cellular redox status during short-term salt stress. Enzymes involved in DNA repair and cell autophagy also contribute to adaptation to short-term salt stress. However, under long-term salt stress, antioxidant enzymes and GSNOR were gradually inactivated through protein S-nitrosylation, leading to oxidative damage and a reduction in cell viability. Modulating the protein S-nitrosylation levels by suppressing GSNOR activity or adding thioredoxin affected the plant's adaptation to salt stress, through altering the redox status and DNA damage and autophagy levels. Based on these data, we propose that unicellular algae use multiple strategies to adapt to salt stress, and that, during this process, GSNOR activity and protein S-nitrosylation levels play important roles.

Transcriptome analysis reveals diversified adaptation of Stipa purpurea along a drought gradient on the Tibetan Plateau.

Natural selection drives species adaptations to biotic and abiotic stresses. Species distributed along a moisture gradient, such as Stipa purpurea, a dominant grass in alpine arid and semi-arid meadows on the Tibetan Plateau, provide an opportunity to evaluate the effects of long-term adaptation to differing degrees of drought stress on gene expression. However, the genetic basis of this divergence remains largely unknown. Next-generation sequencing technologies have provided important genome-wide insights on the evolution of organisms for which genomic information is lacking. To understand how S. purpurea responds to drought stress, we selected five populations distributed along the degressive rainfall line on the northwestern Tibetan Plateau that currently present evolutionary acclimation to localized drought pressure at the physiological and biochemical levels and compared their transcriptome responses. In addition, we performed de novo assembly of the S. purpurea transcriptome using short read sequencing technology and successfully assembled 84,298 unigenes from approximately 51 million sequencing reads. We quantified gene expression level to compare their transcriptome responses using mRNA-Seq and identified differentially expressed transcripts that are involved in primary and secondary plant metabolism, plant hormone synthesis, defense responses, and cell wall synthesis. Furthermore, physiological and biochemical evidence supports that abscisic acid (ABA) accumulation and cell wall strengthening derived from the differential transcripts contribute to the tolerance of S. purpurea to drought stress. The mechanisms by which S. purpurea adapts to drought stress provide new insight into how plants ecologically adapt and evolve.

Comparative proteomic analysis reveals the role of hydrogen sulfide in the adaptation of the alpine plant Lamiophlomis rotata to altitude gradient in the Northern Tibetan Plateau.

MAIN CONCLUSION: We found the novel role of hydrogen sulfide in the adaptation of the alpine plant to altitude gradient in the Northern Tibetan Plateau. Alpine plants have developed strategies to survive the extremely cold conditions prevailing at high altitudes; however, the mechanism underlying the evolution of these strategies remains unknown. Hydrogen sulfide (H2S) is an essential messenger that enhances plant tolerance to environmental stress; however, its role in alpine plant adaptation to environmental stress has not been reported until now. In this work, we conducted a comparative proteomics analysis to investigate the dynamic patterns of protein expression in Lamiophlomis rotata plants grown at three different altitudes. We identified and annotated 83 differentially expressed proteins. We found that the levels and enzyme activities of proteins involved in H2S biosynthesis markedly increased at higher altitudes, and that H2S accumulation increased. Exogenous H2S application increased antioxidant enzyme activity, which reduced ROS (reactive oxygen species) damage, and GSNOR (S-nitrosoglutathione reductase) activity, which reduced RNS (reactive nitrogen species) damage, and activated the downstream defense response, resulting in protein degradation and proline and sugar accumulation. However, such defense responses could be reversed by applying H2S biosynthesis inhibitors. Based on these findings, we conclude that L. rotata uses multiple strategies to adapt to the alpine stress environment and that H2S plays a central role during this process.

Quantitative proteomics analysis reveals that the nuclear cap-binding complex proteins arabidopsis CBP20 and CBP80 modulate the salt stress response.

The cap-binding proteins CBP20 and CBP80 have well-established roles in RNA metabolism and plant growth and development. Although these proteins are thought to be involved in the plant's response to environmental stress, their functions in this process are unclear. Here we demonstrated that Arabidopsis cbp20 and cbp80 null mutants had abnormal leaves and flowers and exhibited increased sensitivity to salt stress. The aberrant phenotypes were more pronounced in the cbp20/80 double mutant. Quantification by iTRAQ (isobaric tags for relative and absolute quantification) identified 77 differentially expressed proteins in the cbp20 and cbp80 lines compared with the wild-type Col-0 under salt stress conditions. Most of these differentially expressed proteins were synergistically expressed in cbp20 and cbp80, suggesting that CBP20 and CBP80 have synergistic roles during the salt stress response. Biochemical analysis demonstrated that CBP20 and CBP80 physically interacted with each other. Further analysis revealed that CBP20/80 regulated the splicing of genes involved in proline and sugar metabolism and that the epigenetic and post-translational modifications of these genes were involved in salt stress tolerance. Our data suggest a link between CBP20/80-dependent protein ubiquitination/sumoylation and the salt stress response.

Differences in Biofilm Formation of Listeria monocytogenes and Their Effects on Virulence and Drug Resistance of Different Strains.

Listeria monocytogenes is recognized as one of the primary pathogens responsible for foodborne illnesses. The ability of L. monocytogenes to form biofilms notably increases its resistance to antibiotics such as ampicillin and tetracycline, making it exceedingly difficult to eradicate. Residual bacteria within the processing environment can contaminate food products, thereby posing a significant risk to public health. In this study, we used crystal violet staining to assess the biofilm-forming capacity of seven L. monocytogenes strains and identified ATCC 19112 as the strain with the most potent biofilm-forming. Subsequent fluorescence microscopy observations revealed that the biofilm-forming capacity was markedly enhanced after two days of culture. Then, we investigated into the factors contributing to biofilm formation and demonstrated that strains with more robust extracellular polymer secretion and self-agglutination capabilities exhibited a more pronounced ability to form biofilms. No significant correlation was found between surface hydrophobicity and biofilm formation capability. In addition, we found that after biofilm formation, the adhesion and invasion of cells were enhanced and drug resistance increased. Therefore, we hypothesized that the formation of biofilm makes L. monocytogenes more virulent and more difficult to remove by antibiotics. Lastly, utilizing RT-PCR, we detected the expression levels of genes associated with biofilm formation, including those involved in quorum sensing (QS), flagellar synthesis, and extracellular polymer production. These genes were significantly upregulated after biofilm formation. These findings underscore the critical relationship between extracellular polymers, self-agglutination abilities, and biofilm formation. In conclusion, the establishment of biofilms not only enhances L. monocytogenes' capacity for cell invasion and adhesion but also significantly increases its resistance to drugs, presenting a substantial threat to food safety.