Cell Wall Modification Research Articles

Molecular insights into Solanum sisymbriifolium’s resistance against Globodera pallida via RNA-seq

BackgroundThe presence of potato cyst nematodes (PCN) causes a significant risk to potato crops globally, leading to reduced yields and economic losses. While the plant Solanum sisymbriifolium is known for its resistance to PCN and can be used as a trap crop, the molecular mechanisms behind this resistance remain poorly understood. In this study, genes differentially expressed were identified in control and infected plants during the early stages of the S. sisymbriifolium - G. pallida interaction.ResultsGene expression profiles were characterized for two S. sisymbriifolium cultivars, Melody and Sis6001, uninfected and infected by G. pallida. The comparative transcriptome analysis revealed a total of 4,087 and 2,043 differentially expressed genes (DEGs) in response to nematode infection in the cultivars Melody and Sis6001, respectively. Gene ontology (GO) enrichment analysis provided insights into the response of the plant to nematode infection, indicating an activation of the plant metabolism, oxidative stress leading to defence mechanism activation, and modification of the plant cell wall. Genes associated with the jasmonic and salicylic acid pathways were also found to be differentially expressed, suggesting their involvement in the plant’s defence response. In addition, the analysis of NBS-LRR domain-containing transcripts that play an important role in hypersensitive response and programmed cell death led to the identification of ten transcripts that had no annotations from the databases, with emphasis on TRINITY_DN52667_C1_G1, found to be upregulated in both cultivars.ConclusionsThese findings represent an important step towards understanding the molecular basis underlying plant resistance to nematodes and facilitating the development of more effective control strategies against PCN.

Exogenous Nitric Oxide Induces Pathogenicity of Alternaria alternata on Huangguan Pear Fruit by Regulating Reactive Oxygen Species Metabolism and Cell Wall Modification.

Black spot caused by Alternaria alternata is one of the most common postharvest diseases in fruit and vegetables. A comprehensive investigation into its pathogenicity mechanism is imperative in order to propose a targeted and effective control strategy. The effect of nitric oxide (NO) on the pathogenicity of A. alternata and its underlying mechanism was studied. The results showed that treatment with 0.5 mM L-1 of sodium nitroprusside (SNP) (NO donor) increased the lesion diameter of A. alternata in vivo and in vitro, which was 22.8% and 13.2% higher than that of the control, respectively. Exogenous NO treatment also induced endogenous NO accumulation by activating nitric oxide synthase (NOS). In addition, NO triggered an increase in reactive oxygen species (ROS) levels. NO enhanced activities and gene expression levels of NADPH oxidase (NOX), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), and glutathione reductase (GR). Moreover, NO stimulated cell wall degrading enzymes by activating the corresponding gene expression in vivo and in vitro. These results suggested that exogenous NO promoted the pathogenicity of A. alternata by inducing ROS accumulation and activating antioxidants and cell wall degrading enzymes. The present results could establish a theoretical foundation for the targeted control of the black spot disease in pear fruit.

Impacts of Fruit Frosting Coverage on Postharvest Softening of Prunes under Vibration Stress

The surface of prune fruit has a thick layer of frosting, which is easily damaged and lost during prunes harvest or postharvest handling, and there is no clear information on the effect of prune surface frost on postharvest storage quality. To investigate the effect of fruit frosting on the softening of prune fruits during storage under vibration stress, prunes were divided into three grades according to fruit frosting in this study and were vibrated for 8 h at a frequency of 5 Hz at 4 °C; then, samples were selected once every 8 d. The results showed that the heavy fruit frosting (HFF) group maintained higher hardness (21.47%), L* (20.85%), and total soluble solids (12.79%) levels at the end of storage and inhibited cell wall-modifying enzyme activities (polygalacturonase, pectin methylesterase, glycosidase, β-glucosidase, and cellulase) compared to frosting-less fruit (FF) group. This group also showed improved expression of key cell wall-modification genes (ADPG2, PME31, CESA1, BGAL3, XTH33, BGLU41) as well as chelate-soluble pectin (72.11%), Na2CO3-soluble pectin (42.83%), and cellulose (36.89%) solubilization and maintained lower water-soluble pectin (34.23%). Microscopic observations showed that the fruit frosting could delay the dissolution of pectin components and protect the cell wall structure. In summary, fruit frosting can effectively inhibit fruit softening and maintain fruit quality.

Xyloglucan endotransglucosylase-hydrolase 1 is a negative regulator of drought tolerance in barley via modulating lignin biosynthesis and stomatal closure

The projected increase in drought severity and duration worldwide poses a significant threat to crop growth and sustainable food production. Xyloglucan endotransglucosylase/hydrolases (XTHs) family is essential in cell wall modification through the construction and restructuring of xyloglucan cross-links, but their role in drought tolerance and stomatal regulation is still illusive. We cloned and functionally characterized HvXTH1 using genetic, physiological, biochemical, transcriptomic and metabolomic approaches in barley. Evolutionary bioinformatics showed that orthologues of XTH1 was originated from Streptophyte algae (e.g. some species in the Zygnematales) the closest clade to land plants based on OneKP database. HvXTH1 is highly expressed in leaves and HvXTH1 is localized to the plasma membrane. Under drought conditions, silencing HvXTH1 in drought-tolerant Tibetan wild barley XZ5 induced a significant reduction in water loss rate and increase in biomass, however overexpressing HvXTH1 exhibited drought sensitivity with significantly less drought-responsive stomata, lower lignin content and a thicker cell wall. Transcriptome profile of the wild type Golden Promise and HvXTH1-OX demonstrated that drought-induced differentially expressed genes in leaves are related to cell wall biosynthesis, abscisic acid and stomatal signaling, and stress response. Furthermore, overexpressing HvXTH1 suppressed both genes and metabolites in the phenylpropanoid pathway for lignin biosynthesis, leading to drought sensitivity of HvXTH1-OX. We provide new insight by deciphering the function of a novel protein HvXTH1 for drought tolerance in cell wall modification, stomatal regulation, and phenylpropanoid pathway for lignin biosynthesis in barley. The function of HvXTH1 in drought response will be beneficial to develop crop varieties adapted to drought.

Brassinosteroids mediate arbuscular mycorrhizal symbiosis through multiple potential pathways and partial identification in tomato

Currently, little is known regarding the specific processes through which brassinosteroids (BR) affect arbuscular mycorrhizal (AM) symbiosis. Understanding this relationship is vital for advancing plant physiology and agricultural applications. In this study, we aimed to elucidate the regulatory mechanisms of BR in AM symbiosis. According to the log2 fold change-value and adjP-value, we integrated the common differentially expressed genes (DEGs) in maize (Zea mays L.) treated with BR and AM, Arabidopsis (Arabidopsis thaliana) mutants deficient in BR receptors, and tomato (Solanum lycopersicum) plants inoculated with AM fungi. In addition, we characterized the symbiotic performance of tomato plants with BR receptor defects and overexpression. The results indicated that the common differential genes induced by BR and AM were involved in metabolic processes, such as cell wall modification, cytoskeleton remodeling, auxin and ethylene signaling, photosynthesis, mineral nutrient transport, and stress defense. Specifically, these include the BR1 gene, which modifies the cell wall. However, the fungal colonization rate of BR receptor-deficient tomato plants was significantly reduced, and the total phosphorus concentration was increased. Conversely, the performance of the overexpressing tomato transformation plants demonstrated a significant contrast. Additionally, the mild rescue of mycorrhizal attenuation in mutants treated with exogenous BR suggests the possibility of direct feedback from BR synthesis to AM. Notably, the cell wall modification gene (SlBR1) and calcium spike gene (SlIPD3) were induced by both BR and AM, suggesting that BR may influence cell penetration during the early stages of AM colonization. Synthesis: Our results demonstrated that BR positively regulates AM symbiosis through multiple pathways. These findings pave the way for future research, including isolation of the individual contributions of each pathway to this complex process and exploration of possible agricultural applications.

Host-Parasite interaction between brown algae and eukaryote biotrophic pathogens

Brown algae belong to the class Phaeophyceae which are mainly multicellular, photosynthetic organisms, however they evolved independently from terrestrial plants, green and red algae. In the past years marine aquaculture involving brown algae has gained enormous momentum. In both natural environments and aquaculture, brown algae are susceptible to infection by various prokaryotic and eukaryotic parasites. While our understanding of host-parasite interactions in brown algae is gaining recognition, our understanding of how brown algae react to biotic stress remains incomplete. The objective of this review is to address research gaps in the field by providing a summary of what is already known about the response of brown algae to abiotic and biotic stress. The biology of eukaryotic zoosporic pathogens Maullinia ectocarpii, Eurychasma dicksonii, Anisolpidium ectocarpii is also discussed, as those parasites have been used in laboratory experiments to study diseases of brown algae. These studies often relied on parasites-infecting Ectocarpus siliculosus which has become a brown algal model organism to study host-pathogen interactions. Stress response in brown algae involves processes similar to hypersensitivity response, oxidative stress response and activation of peroxidases, but also the production of blue fluorescent metabolites and deposition of β-1,3-glucan in the cell wall. Cell wall modification, expression of several defence related proteins, and secondary metabolite production also holds a crucial role in brown algal defence mechanism. Understanding host-pathogen interactions and the associated mechanisms is vital to discover strategies to control pathogens in the growing aquaculture sector.

Overexpression of OsGASR1 promotes Al tolerance in rice

Aluminum (Al) toxicity in acid soils poses a significant threat to rice, which exhibits highly complex genetic mechanisms for both external detoxification and internal tolerance among cereal crops. Although several genes involved Al tolerance have been identified, the molecular mechanisms underlying Al tolerance in rice remain to be fully explored. Here, we functionally characterized the gibberellin-stimulated transcription gene OsGASR1, which encodes a small cysteine-rich peptide localized to the nucleus and cytoplasm and plays a significant role in Al tolerance in rice. The expression of OsGASR1 is rapidly up-regulated by Al in rice root tips but not in the shoots. Its expression is not regulated by the central regulator Aluminum Resistance Transcription Factor 1 (ART1), indicating that OsGASR1 functions as a novel gene in rice Al resistance independent of ART1. Knockout of OsGASR1 reduced root length but did not affect Al tolerance in rice, whereas overexpression of OsGASR1 enhanced Al tolerance without affecting Al distribution and accumulation and promoted the accumulation of reactive oxygen species (ROS) in the root tips. RNA-seq analysis revealed that overexpression of OsGASR1 upregulated the expression of genes associated with cell wall modification, oxidative stress, and Al tolerance. Collectively, these findings suggest that OsGASR1 is involved in Al tolerance in rice independently of ART1, and the up-regulation of this gene is necessary for rice Al tolerance.

Phosphorus uptake 1 (Pup1) QTL performs major regulatory functions under phosphorus starvation/deficiency stress in rice (Oryza sativa L.)

Phosphorus (P) is an essential macronutrient required for respiration, photosynthesis/carbohydrate metabolism, redox homeostasis, signaling, and synthesis/function of nucleic acids, cellular membranes, enzymes, etc. To cope with P-deficiency, plants reprogram gene expression for necessary alterations in metabolic/signaling pathways. To attain P homeostasis, plants readjust metabolism through transcriptional, post-transcriptional, and/or post-translational machinery involving biochemical, physiological, genomic, epigenomic, proteomic, and metabolomic functions. However, the underlying molecular mechanisms/pathways/genes for P-deficiency tolerance in crop plants remain elusive. To decipher the mechanisms/pathways adopted by rice under P-starvation/deficiency stress, a pair of contrasting rice [Pusa-44 (high-yielding, P-deficiency sensitive) and its near-isogenic line (NIL)-23, P-deficiency tolerant) for Pup1 QTL] genotype was used for comparative analyses. Omics analyses of shoot and root tissues from 45-day-old plants grown hydroponically in P-sufficient (16 ppm Pi), P-deficient (4 ppm Pi) or P-starved (0 ppm Pi) medium revealed important roles of P transporters, transcription factors (TFs), Transposable elements (TEs), auxin-responsive proteins, cell wall modulation, fatty acid metabolism, and chromatin architecture/epigenetic modifications in making NIL-23 tolerant to stress. The proteins involved in photosynthesis, sucrose-/starch-/energy-metabolism, transcription factors, and phytohormone signaling were observed to be differentially expressed in NIL-23. Since only a few coding genes are located on the QTL, modulations in morpho-physio-biochemical and molecular parameters under P-starvation/deficiency stress were attributed to the regulatory functions of Pup1 through TFs, TEs, epigenetic/chromatin architectural changes, etc. introgressed in Pusa-44 genetic background. Thus, the study provides new insights into molecular/regulatory functions of Pup1 under P-starvation/deficiency stress in rice, which might be useful to improve P-use efficiency in rice for better productivity in P-deficient soils.

Potent pollen gene regulation by DNA glycosylases in maize

Although DNA methylation primarily represses TEs, it also represses select genes that are methylated in plant body tissues but demethylated by DNA glycosylases (DNGs) in endosperm or pollen. Either one of two DNGs, MATERNAL DEREPRESSION OF R1 (MDR1) or DNG102, is essential for pollen viability in maize. Using single-pollen mRNA sequencing on pollen-segregating mutations in both genes, we identify 58 candidate DNG target genes that account for 11.1% of the wild-type transcriptome but are silent or barely detectable in other tissues. They are unusual in their tendency to lack introns but even more so in their TE-like methylation (teM) in coding DNA. The majority have predicted functions in cell wall modification, and they likely support the rapid tip growth characteristic of pollen tubes. These results suggest a critical role for DNA methylation and demethylation in regulating maize genes with the potential for extremely high expression in pollen but constitutive silencing elsewhere.

Drought response of tuber genes in processing potatoes (Solanum tuberosum L.) in Japan.

Limited crop production due to lower rainfall has a major impact on the supply and demand of food for the human population. In potato (Solanum tuberosum L.), one of the major crops, there is also concern about a lack of production due to drought stress. Especially the cultivar "Toyoshiro" suitable for processing, has significant reduction in drought yield. Therefore, it is necessary to understand the mechanism of gene expression changes that occur in potato "Toyoshiro" plants and tubers during drought. Seed potatoes were split in half and one was used as a control plant (CT), and the other was used as a drought-stressed plant (DS). CT was watered daily, and DS watered off to mimic the weather conditions of the Tokachi-Obihiro region in 2021. These tubers were harvested at week 14 and the transcriptome was analyzed. DS plants showed 423 downregulated genes and 197 upregulated genes compared to CT. Factors related to cell wall modification, heat stress response, and phytosterol metabolism were detected among the genes whose expression changed. Moreover, the expression of "Abscisic acid and environmental stress-inducible protein TAS14 like (TAS14)," a molecule reported to be upregulated under drought stress, was also upregulated, and was upregulated expression in all strains that reproduced drought. The localization of this molecule in the nucleus and plasma membrane was confirmed in a mCherry-tagged TAS14 mutant line. Our findings contribute to understanding the survival strategy system of Japanese processing potatoes in response to drought stress.

Precise cell wall modification of bamboo through two-step furfurylation via solution quantitative adsorption

Improving the dimensional stability of bamboo for construction and engineering use through furfurylation is crucial. Traditional methods like impregnation and soaking furfurylation are hindered by high modifier consumption and waste disposal issues. In this study, we propose a novel technique called solution quantitative adsorption furfurylation (SQAF) to enhance bamboo's dimensional stability and overcome these challenges. Our findings indicate that SQAF achieves enhanced dimensional stability (anti-swelling efficiency (ASE) up to 53.02 %) and reduced hygroscopicity (EMC down to 4.11 %) with approximately 12.50 % weight percentage gain (WPG), and a high furfuryl alcohol (FA) utilization efficiency (SR > 85 %). Analysis using SEM and nanoindentation reveals precise modification of the cell walls without FA resin accumulating in cell cavities. Additionally, SQAF allows for a graded distribution of FA resin, thereby improving the physical properties of bamboo while maintaining its mechanical integrity, especially as the decline in toughness of bamboo is reduced by more than 40 % compared to traditional methods.

Comparative Analysis of the Aspergillus fumigatus Cell Wall Modification and Ensuing Human Dendritic Cell Responses by β-(1,3)-Glucan Synthase Inhibitors-Caspofungin and Enfumafungin.

Caspofungin, a lipopeptide, is an antifungal drug that belong to the class of echinocandin. It inhibits fungal cell wall β-(1,3)-glucan synthase activity and is the second-line of drug for invasive aspergillosis, a fatal infection caused mainly by Aspergillus fumigatus. On the other hand, Enfumafungin is a natural triterpene glycoside also with a β-(1,3)-glucan synthase inhibitory activity and reported to have antifungal potential. In the present study, we compared the growth as well as modifications in the A. fumigatus cell wall upon treatment with Caspofungin or Enfumafungin, consequentially their immunomodulatory capacity on human dendritic cells. Caspofungin initially inhibited the growth of A. fumigatus, but the effect was lost over time. By contrast, Enfumafungin inhibited this fungal growth for the duration investigated. Both Caspofungin and Enfumafungin caused a decrease in the cell wall β-(1,3)-glucan content with a compensatory increase in the chitin, and to a minor extent they also affected cell wall galactose content. Treatment with these two antifungals did not result in the exposure of β-(1,3)-glucan on A. fumigatus mycelial surface. Enzymatic digestion suggested a modification of β-(1,3)-glucan structure, specifically its branching, upon Enfumafungin treatment. While there was no difference in the immunostimulatory capacity of antifungal treated A. fumigatus conidia, alkali soluble-fractions from Caspofungin treated mycelia weakly stimulated the dendritic cells, possibly due to an increased content of immunosuppressive polysaccharide galactosaminogalactan. Overall, we demonstrate a novel mechanism that Enfumafungin not only inhibits β-(1,3)-glucan synthase activity, but also causes modifications in the structure of β-(1,3)-glucan in the A. fumigatus cell wall.

Genome-wide identification and characterization of pectin methylesterase inhibitor gene family members related to abiotic stresses in watermelon.

Pectin is a vital component of plant cell walls and its methylation process is regulated by pectin methylesterase inhibitors (PMEIs). PMEIs regulate the structural and functional modifications of cell walls in plants and play an important role in plant processes such as seed germination, fruit ripening, and stress response. Although the PMEI gene family has been well characterized in model plants, the understanding of its molecular evolution and biological functions in watermelon remains limited. In this study, 60 ClPMEI genes were identified and characterized, revealing their dispersion on multiple chromosomes. Based on a systematic developmental analysis, these genes were classified into three subfamilies, which was further supported by the exon, intron, and conserved motif distribution. Analysis of cis-elements and expression patterns indicated that ClPMEIs might be involved in regulating the tolerance of watermelon to various abiotic stresses. Moreover, distinct ClPMEI genes exhibit specific functions under different abiotic stresses. For example, ClPMEI51 and ClPMEI54 showed a significant upregulation in expression levels during the late stage of drought treatments, whereas ClPMEI3 and ClPMEI12 displayed a significant downregulation under low-temperature induction. Subcellular localization prediction and analysis revealed that the ClPMEI family member proteins were localized to the cell membrane. This study provided an important foundation for the further exploration of the functions of ClPMEI genes in watermelon.

Genomic Insights into Disease Resistance in Sunflower (Helianthus annuus): Identifying Key Regions and Candidate Genes for Verticillium dahliae Resistance.

Sunflower (Helianthus annuus) is a globally significant field crop, and disease resistance is crucial for ensuring yield stability and crop quality. Verticillium dahliae is a notorious soilborne pathogen that causes Verticillium Wilt (VW) and threatens sunflower production worldwide. In this study, we conducted a comprehensive assessment of sunflower resistance to V. dahliae across 231 sunflower cultivar lines, from the Sunflower Association Mapping (SAM) population. We employed EMMAX and ridge regression best linear unbiased prediction (rrBLUP) and identified 148 quantitative trait loci (QTLs) and 23 putative genes associated with V. dahliae resistance, including receptor like kinases, cell wall modification, transcriptional regulation, plant stress signalling and defense regulation genes. Our enrichment and quantitative real-time PCR validation results highlight the importance of membrane vesicle trafficking in the sunflower immune system for efficient signaling and defense upon activation by V. dahliae. This study also reveals the polygenic architecture of V. dahliae resistance in sunflowers and provides insights for breeding sunflower cultivars resistant to VW. This research contributes to ongoing efforts to enhance crop resilience and reduce yield losses due to VW, ultimately benefiting sunflower growers and the agricultural sector.

WOX11-mediated cell size control in Arabidopsis attenuates growth and fecundity of endoparasitic cyst nematodes.

Cyst nematodes establish permanent feeding structures called syncytia inside the host root vasculature, disrupting the flow of water and minerals. In response, plants form WOX11-mediated adventitious lateral roots at nematode infection sites. WOX11 adventitious lateral rooting modulates tolerance to nematode infections; however, whether this also benefits nematode parasitism remains unknown. Here, we report on bioassays using a 35S::WOX11-SRDX transcriptional repressor mutant to investigate whether WOX11 adventitious lateral rooting promotes syncytium development and thereby female growth and fecundity. Moreover, we chemically inhibited cellulose biosynthesis to verify if WOX11 directly modulates cell wall plasticity in syncytia. Finally, we performed histochemical analyses to test if WOX11 mediates syncytial cell wall plasticity via reactive oxygen species (ROS). Repression of WOX11-mediated transcription specifically enhanced the radial expansion of syncytial elements, increasing both syncytium size and female offspring. The enhanced syncytial hypertrophy observed in the 35S::WOX11-SRDX mutant could be phenocopied by chemical inhibition of cellulose biosynthesis and was associated with elevated levels of ROS at nematode infection sites. We, therefore, conclude that WOX11 restricts radial expansion of nematode-feeding structures and female growth and fecundity, likely by modulating ROS-mediated cell wall plasticity mechanisms. Remarkably, this novel role of WOX11 in plant cell size control is distinct from WOX11 adventitious lateral rooting underlying disease tolerance.

Chitosan stimulates root hair callose deposition, endomembrane dynamics, and inhibits root hair growth.

Although angiosperm plants generally react to immunity elicitors like chitin or chitosan by the cell wall callose deposition, this response in particular cell types, especially upon chitosan treatment, is not fully understood. Here we show that the growing root hairs (RHs) of Arabidopsis can respond to a mild (0.001%) chitosan treatment by the callose deposition and by a deceleration of the RH growth. We demonstrate that the glucan synthase-like 5/PMR4 is vital for chitosan-induced callose deposition but not for RH growth inhibition. Upon the higher chitosan concentration (0.01%) treatment, RHs do not deposit callose, while growth inhibition is prominent. To understand the molecular and cellular mechanisms underpinning the responses to two chitosan treatments, we analysed early Ca2+ and defence-related signalling, gene expression, cell wall and RH cellular endomembrane modifications. Chitosan-induced callose deposition is also present in the several other plant species, including functionally analogous and evolutionarily only distantly related RH-like structures such as rhizoids of bryophytes. Our results point to the RH callose deposition as a conserved strategy of soil-anchoring plant cells to cope with mild biotic stress. However, high chitosan concentration prominently disturbs RH intracellular dynamics, tip-localised endomembrane compartments, growth and viability, precluding callose deposition.

Over-expression of LsEXPA6, a lettuce expansin gene, improves cadmium stress tolerance in transgenic Arabidopsis

Cadmium (Cd) is a harmful heavy metal that is highly toxic to plants and animals. Expansins are cell wall proteins inducing cell wall loosening and participate in all plant growth and development processes which are associated with cell wall modifications. We investigated lettuce’s expansin gene LsEXPA6 and found that LsEXPA6 overexpression Arabidopsis lines were much more resistant to cadmium stress. Our results revealed that the root system of the expa6 mutant was suppressed under cadmium stress, resulting in shorter plant height, reduced biomass, and a significant increase in cadmium content in the plants compared with wild-type plants, whereas LsEXPA6 overexpression lines had a well-developed root system and reduced cadmium accumulation in the roots and shoots of the plants. The above results indicated that overexpression of LsEXPA6 affected root development and reduced Cd absorption in Arabidopsis. In addition, the higher absorption capacity of nutrients, increased antioxidant enzymes activities, improved chlorophyll and photosynthetic function in the overexpression Arabidopsis plants, supported the Cd stress tolerance mechanism. Taken together, these results provided a new insight on the role of expansin proteins in the tolerance of plants to Cd stress by root cell elongation.

Evaluating the accuracy of the MBT Lipid Xtract Kit for assessing colistin resistance in comparison to broth microdilution.

Colistin resistance testing methods such as broth microdilution (BMD) are time-consuming and labour intensive for clinical laboratories. MBT Lipid Xtract Kit on MALDI Biotyper Sirius System (Bruker, Billerica, MA, USA) utilizes lipidomic analysis to identify specific cell wall modifications associated with colistin resistance. We compared MBT to BMD (ComASP Colistin, Liofilchem) across 36 Gram-negative isolates (non-resistant MIC ≤2 µg ml-1, resistant MIC ≥4 µg ml-1). All samples were tested twice on MBT with discrepant results repeated before assessing categorical agreement between MBT and BMD. 44.4% (16/36) of isolates were colistin resistant via BMD. MBT Lipid Xtract had 80.6% agreement (29/36) with BMD, with 5/7 discrepancies corrected to match upon repeat testing. There was 100% agreement for Escherichia coli isolates (n=16). The whole-genome sequencing was completed on the two discrepant Klebsiella pneumoniae isolates, with variants within colistin resistance-associated loci identified (MIC 0.5 µg ml-1: arnC S30T, pmrB T246A, lapB N212T, lpxM S253G, crrB Q287K and MIC >16 µg ml-1: arnC S30T, pmrB R90insRN, pmrB T246A, pmrA E57G, lpxM S253G). Further evaluation, particularly for non-E. coli, of MBT is required prior to implementation in clinical laboratories.

Bilberry metabolomic and proteomic profiling during fruit ripening reveals key dynamics affecting fruit quality.

Bilberry (Vaccinium myrtillus L.) is a wildberry species that is prevalent in northern Europe. It is renowned and well-documented for its nutritional and bioactive properties, especially due to its anthocyanin content. However, an overview of biological systems governing changes in other crucial quality traits, such as size, firmness, and flavours, has received less attention. In the present study, we investigated detailed metabolomic and proteomic profiles at four different ripening stages of bilberry to provide a comprehensive understanding of overall quality during fruit ripening. By integrating omics datasets, we revealed a novel global regulatory network of plant hormones and physiological processes occurring during bilberry ripening. Key physiological processes, such as energy and primary metabolism, strongly correlate with elevated levels of gibberellic acids, jasmonic acid, and salicylic acid in unripe fruits. In contrast, as the fruit ripened, processes including flavour formation, cell wall modification, seed storage, and secondary metabolism became more prominent, and these were associated with increased abscisic acid levels. An indication of the increase in ethylene biosynthesis was detected during bilberry development, raising questions about the classification of non-climacteric and climacteric fruits. Our findings extend the current knowledge on the physiological and biochemical processes occurring during fruit ripening, which can serve as a baseline for studies on both wild and commercially grown berry species. Furthermore, our data may facilitate the optimization of storage conditions and breeding programs, as well as the future exploration of beneficial compounds in berries for new applications in food, cosmetics, and medicines.

Low concentrations of methyl jasmonate promote plant growth and mitigate Cd toxicity in Cosmos bipinnatus

Cadmium (Cd) is a biologically non-essential heavy metal, a major soil pollutant, and extremely harmful to plants. The phytohormone methyl jasmonate (MeJA) plays an important role in plant heavy-metal resistance. However, the understanding of the effects of MeJA supply level on alleviating Cd toxicity in plants is limited. Here, we investigated how MeJA regulated the development of physiological processes and cell wall modification in Cosmos bipinnatus. We found that low concentrations of MeJA increased the dry weight of seedlings under 120 µM Cd stress by reducing the transport of Cd from roots to shoots. Moreover, a threshold concentration of exogenous MeJA increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in plant roots, the concentration of Cd in the root cell wall, and the contents of pectin and hemicellulose 1 polysaccharides, through converting Cd into pectin-bound forms. These results suggested that MeJA mitigated Cd toxicity by modulating root cell wall polysaccharide and functional group composition, especially through pectin polysaccharides binding to Cd, with effects on Cd transport capacity, specific chemical forms of Cd, and homeostatic antioxidant systems in C. bipinnatus.