Search Results (273)

Common bean (Phaseolus vulgaris L.) is a critical protein-rich legume supporting food and nutritional security globally. However, Fusarium wilt, caused by Fusarium solani, remains a major constraint to production, with yield losses reaching up to 84%. While biocontrol strategies have been explored, most microbial agents are sourced from mesophilic environments and show limited effectiveness under abiotic stress. Here, we report the isolation and characterization of extremophilic Bacillus spp. from the hypersaline Lake Bogoria, Kenya, and their biocontrol potential against F. solani. From 30 isolates obtained via serial dilution, 9 exhibited antagonistic activity in vitro, with mycelial inhibition ranging from 1.07–1.93 cm 16S rRNA sequencing revealed taxonomic diversity within the Bacillus genus, including unique extremotolerant strains. Molecular screening identified genes associated with the biosynthesis of antifungal metabolites such as 2,4-diacetylphloroglucinol, pyrrolnitrin, and hydrogen cyanide. Enzyme assays confirmed substantial production of chitinase (1.33–3160 U/mL) and chitosanase (10.62–28.33 mm), supporting a cell wall-targeted antagonism mechanism. In planta assays with the lead isolate (B7) significantly reduced disease incidence (8–35%) and wilt severity (1–5 affected plants), while enhancing root colonization under pathogen pressure. These findings demonstrate that extremophile-derived Bacillus spp. possess robust antifungal traits and highlight their potential as climate-resilient biocontrol agents for sustainable bean production in arid and semi-arid agroecosystems. Full article

Powdery mildew (PM), caused by Sphaerotheca phaseoli, severely threatens mungbean (Vigna radiata) productivity and quality, yet the molecular basis of resistance remains poorly defined. This study employed transcriptome profiling to compare defense responses in a resistant genotype, SUPER5, and a susceptible variety, CN84-1, following pathogen infection. A total of 1755 differentially expressed genes (DEGs) were identified, with SUPER5 exhibiting strong upregulation of genes encoding pathogenesis-related (PR) proteins, disease resistance proteins, and key transcription factors. Notably, genes involved in phenylpropanoid and flavonoid biosynthesis, pathways associated with antimicrobial compound and lignin production, were markedly induced in SUPER5. In contrast, CN84-1 showed limited activation of defense genes and downregulation of essential regulators such as MYB14. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses highlighted the involvement of plant–pathogen interaction pathways, MAPK signaling, and reactive oxygen species (ROS) detoxification in the resistant response. Quantitative real-time PCR validated 11 candidate genes, including PAL3, PR2, GSO1, MLO12, and P21, which function in pathogen recognition, signaling, the biosynthesis of antimicrobial metabolites, the production of defense proteins, defense regulation, and the reinforcement of the cell wall. Co-expression network analysis revealed three major gene modules linked to flavonoid metabolism, chitinase activity, and responses to both abiotic and biotic stresses. These findings offer valuable molecular insights for breeding PM-resistant mungbean varieties. Full article

The purpose of this study was to investigate the growth-promoting effects of four rhizobacterial isolates (RS60, RS65, RS46, and RP6) isolated from the tomato rhizosphere. These isolates were screened for key plant growth-promoting rhizobacteria (PGPR) mechanisms, including ammonia production, nitrogen fixation, phosphate solubilization, indole-3-acetic acid (IAA) production, and siderophore synthesis. Their potential to enhance seed germination and tomato plant growth was investigated in controlled and greenhouse conditions. Four isolates exhibited multiple PGPR attributes, notably IAA and ammonia production as well as phosphate solubilization. The results revealed that these strains significantly enhanced tomato seed germination and shoot growth in vitro, with RS65 showing the highest germination rate (70%). However, no significant differences in early seedling responses were observed under greenhouse conditions when compared to the control. Thirty days after inoculation, greenhouse results revealed that the four studied strains significantly increased growth metrics including shoot length, number of leaves, collar diameter, and dry weight. The isolate RP6 showed a significant effect on the growth of the plant, with an average shoot length of 34.40 cm and nine leaves per plant. In vitro antagonism assays demonstrated that isolates RS60, RS65, and RP6 effectively inhibited the growth of Botrytis cinerea, Alternaria alternata, and Oidium lycopersici, with inhibition rates exceeding 65%. These antagonistic activities were linked to the production of hydrolytic enzymes (chitinase, cellulase, pectinase, protease), siderophores, and hydrogen cyanide (HCN). Molecular identification through 16S rRNA gene sequencing confirmed the isolates as Bacillus cereus (RS60), Bacillus pumilus (RS46), Bacillus amyloliquefaciens (RP6), and Bacillus velezensis (RS65), each showing over 97% sequence similarity with reference strains. These findings underscore the potential of the selected Bacillus spp. as promising biofertilizers and biocontrol agents for sustainable tomato cultivation and support their inclusion in integrated disease and nutrient management strategies. Full article

The effects of a fungal elicitor from Trichothecium roseum on signal pathways of salicylic acid (SA), jasmonic acid (JA), and Ca²⁺ in potato tubers were investigated. The results showed that fungal elicitor treatment effectively inhibited the lesion diameter of Fusarium sulphureum in vivo, which was 17.5% lower than that of the control. In addition, fungal elicitor treatment triggered an increase in O₂⁻ production and H₂O₂ content. The fungal elicitor enhanced the activities and gene expression levels of isochorismate synthase (ICS), phenylalanine ammonia lyase (PAL), allene oxide cyclase (AOC), allene oxide synthase (AOS), lipoxygenase (LOX), and Ca²⁺-ATPase. Furthermore, the fungal elicitor promoted an increase in calmodulin (CaM) content. Protective enzymes (dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), chitinase (CHI), and β-1,3-glucanase (Glu)) and disease-resistance-related genes (PR1, PR2, and PDF1.2) were induced to be upregulated by elicitor treatment. These results indicated that the fungal elicitor induced disease resistance by accelerating the accumulation of reactive oxygen species (ROS), activating SA, JA, and Ca²⁺ signaling, and upregulating resistance genes. The results of this study revealed the molecular mechanism of fungal elicitor-induced resistance in the potato, which provides a theoretical basis for the mining of new, safe, and efficient elicitor-sourced antifungal agents and is of great importance for the effective control of potato dry rot disease. Full article

Lanzhou lily is a plant native to China with high edible, medicinal, and ornamental value that is relatively susceptible to Fusarium wilt. In this study, the application of Trichoderma longibrachiatum SMF2 (TlSMF2) effectively controlled Lanzhou lily wilt disease caused by Fusarium oxysporum and F. solani. TlSMF2 and the antimicrobial peptaibols trichokonins (TKs) produced by TlSMF2 inhibited the mycelial growth and spore germination of these two pathogens. Transcriptome analysis revealed that the TKs-induced defense responses of Lanzhou lily were mainly related to the production of plant hormones and defense enzymes. In detail, TKs treatment increased the levels of salicylic acid (SA) and jasmonic acid (JA) and the expression of their related genes and upregulated the activities of chitinase and phenylalanine ammonia-lyase (PAL). Moreover, TKs caused the induction of LzWRKY26 and LzWRKY75, which is highly homologous to LrWRKY3 that positively regulates Lilium regale resistance to F. oxysporum. LzWRKY26 expression was also induced by SA and MeJA treatments and F. oxysporum infection, which was consistent with the findings that many cis-acting elements associated with phytohormones and stress responses are present in the promoter region of LzWRKY26. Therefore, the biocontrol mechanisms of TlSMF2 against Lanzhou lily wilt disease involve substrate competition and toxicity against pathogens, as well as the induction of systemic resistance in plants. Our results highlight a promising biological control agent for soil-borne fungal diseases and offer deeper insights into the biocontrol mechanisms of TlSMF2. Full article

The biotechnological applications of chitinases are diverse. They are used in industrial sectors such as pharmaceuticals, textiles, and agriculture, including the use of recombinant chitinases for pest control, since traditional treatments affect and contaminate hive products. Bacillus licheniformis UV01 bacterium is of interest, as it expresses genes for different enzymes, including chitinase. The Chibluv01 gene was cloned into the pHTP8 vector with a His/tag for purification using affinity chromatography. It showed a specific activity of 115 U/m. The optimal pH and temperature were 7.5 and 42 °C, respectively. The choleoptericidal activity (ability to kill beetles) of the enzyme was evaluated in the larvae and adult beetles of Aethina tumida treated with immersion in a purified enzyme extract at different concentrations, and the mortality was verified at 24, 48, and 72 h. Within 24 h of application, the mortality increased by 50% in the larval stage and 56.6% in adult beetles compared to the control groups. The LC₅₀ and LC₉₀ were obtained: 104.05 U/mL and 234.36 U/mL in larvae and 92.99 U/mL and 211.14 U/mL in adults, respectively. These results indicate the potential of the application of ChiBlUV02 chitinase in pest control. Full article

Black spot is a major postharvest disease of cherry tomatoes, caused by Alternaria alternata. This causes economic losses and storage challenges, so researchers are exploring alternative methods. The biological control of fruits and vegetables using antagonistic bacteria and yeasts is currently a research hotspot. Initially, the biological control impact of Bacillus velezensis T3 on cherry tomato black spot was investigated. Disease defense, scavenging reactive oxygen species, and antioxidant-related enzymes were determined during different storage periods. The relative gene expressions of these enzymes were also confirmed using RT-qPCR. The results showed that B. velezensis T3 reduced the incidence of black spot disease in cherry tomatoes. The growth of A. alternata was suppressed by B. velezensis T3 cell-free filtrate both in vitro and in vivo. In addition, B. velezensis T3 induced the activities of disease resistance-related enzymes such as polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU), and chitinase (CHI), and the activities of the ROS-related enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), and reduced the rate of O₂⁻ production and H₂O₂, and MDA content of cherry tomatoes. This approach offers a promising alternative for extending shelf life, though further studies are needed to fully characterize its effects on fruit quality. Full article

Stemphylium lycopersici is the causal pathogen of the devastating tomato gray leaf spot with a wide range of alternative plant hosts. To mitigate its potential endemic in facility-cultivated tomatoes, novel disease control strategies should be attempted to minimize the use of chemical fungicides. In this study, we identified a metalloprotease from S. lycopersici genome and designated it as SlMEP1, as it appears to be a typical zinc metalloproteinase containing a WLM (WSS1-like metalloprotease) domain and a characteristic HEXXH motif, which we determined by analyzing its transcriptional profile and enzymatic functions. The transcription level of SlMEP1 increased greatly during the fungal invasion of tomato leaves. The deletion of the SlMEP1 gene from S. lycopersici hindered its mycelial growth and reduced its pathogenicity. An assessment of the functional dissection indicated that SlMEP1 induced cell collapse and inhibited the expression of the host chitinases, which consequently made tomato cells more susceptible to S. lycopersici and other pathogenic fungi. Full article

Chitinases are enzymes that catalyze the hydrolysis of chitin and play a significant biophysiological role in fungal growth, development, and pathogenesis. Valsa mali is a necrotrophic fungus that is a primary contributor to apple Valsa canker. Our study focused on the identification of chitinase gene families from V. mali and the analysis of their expression profiles during infection and nutritional growth. A phylogenetic analysis and conservation of catalytic domains were used to classify these genes into three classes, and their chromosome distribution was random. The qRT-PCR analysis identified five differentially expressed VmGH18 genes during infection and nutritional growth. GH18 chitinases use glutamate, whereas VmGH18-4 (VM1G_05900) and VmGH18-10 (VM1G_03597) use glutamine as the catalytic motif. To further test whether it can induce cell death in apple, the recombinant protein was produced in E. coli. It showed that the purified VmGH18-4 recombinant protein retained cell-death inducing activity, and it could also induce cell death in apple. But the enzyme activity shows that neither VmGH18-4 nor VmGH18-10 have chitinases enzyme activity. These results suggest that VmGH18-4 can elicit cell death in multiple plant species, while VmGH18-10 cannot. Full article

Pleurotus ostreatus is the third largest cultivated species in China’s edible mushroom industry; however, its agricultural cultivation method is easily affected by high-temperature environments. To understand the response mechanism of mycelia to heat stress, the mycelia of P. ostreatus, which had been grown at 28 °C for 4 days, were subjected to heat stress at 32 °C and 36 °C for 2 days, followed by RNA-seq analysis. These results indicate that, under heat stress, mycelial growth was significantly inhibited, the cell membrane was disrupted, the cell walls became thicker, and chitinase and β-1,3-glucanase activities decreased. Transcriptome analysis revealed 2118 differentially expressed genes (DEGs) under 36 °C heat stress, and 458 DEGs were identified under 32 °C heat stress. A total of 328 DEGs were upregulated or downregulated under heat stress at 36 °C and 32 °C. The functional enrichment analysis of these genes revealed significant enrichment in genes related to hydrogen peroxide metabolism, oxidoreductase activity, ATP hydrolysis, and cell wall structure composition. There was a total of 80 DEGs specific to heat stress at 32 °C, and they were significantly enriched in catalase activity, the cell wall, the aminoglycan catabolic process, and oxidoreductase activity. However, 817 DEGs specific to heat stress at 36 °C were significantly enriched in the cell wall, integral components of the membrane, and oxidoreductase activity. The identification of cell wall-related genes revealed that hydrophobic proteins, Cerato plateau proteins, laccases, and glycoside hydrolases may respond to stress. The results of qRT-PCR for cell wall-related genes are consistent with the RNA-seq data. This study revealed several potential candidate genes for high-temperature thermal response, laying the foundation for the study of the thermal response mechanism of P. ostreatus. Full article

Despite its ecological and economic importance, many aspects of Varroa destructor’s biology remain poorly understood, particularly its defense mechanisms against pathogens. The limited knowledge of Varroa’s immunity has hindered the development of RNA interference (RNAi)-based strategies targeting immune-related genes. In this study, we investigated the immune gene repertoire of V. destructor by querying its NCBI nr protein database and comparing it to model species of ticks (Ixodes scapularis) and mites (Galendromus occidentalis and Tetranychus urticae). Transcription of candidate immune genes was confirmed by analyzing a de novo assembled transcriptome of V. destructor. Our findings reveal that V. destructor shares key immunological traits with ticks, including lysozymes, chitinases, and thioester-containing proteins (TEPs), but also shares the absence of transmembrane peptidoglycan recognition proteins (PGRPs), Gram-negative binding proteins, and several lectin families involved in pathogen recognition. Additionally, Varroa mites, like ticks, lack homologs of crucial immune signaling components, such as the unpaired ligand (JAK/STAT), Eiger (JNK), and multiple elements of the IMD pathway. They also do not encode canonical antimicrobial peptides (AMPs) like defensins but possess putative homologs of ctenidins, AMPs previously identified in spiders and ticks, which may be adopted as a novel genetic readout for immune response in mites. Our findings lay the groundwork for future functional studies on mite immunity and open new avenues for RNAi-based biocontrol strategies targeting immune pathways to enhance Varroa management. Full article

Chitin represents a globally abundant marine polymer with significant ecological and biotechnological value. β-chitin is an important carbon fixation product of diatoms and has a greater range of applications than α- and γ-chitin. However, there has been a paucity of research on the characterization of chitin-related enzymes from β-chitin producers. In this study, we performed a genome-wide identification of 38 putative chitinase genes in Thalassiosira weissflogii, a key producer of β-chitin. Through comprehensive analyses of phylogenetic relationships, conserved motifs, structural domains, and subcellular localization predictions, we revealed that T. weissflogii possesses evolutionarily distinct GH18 and GH19 chitinase families exhibiting unique motif and domain configurations. Subcellular localization predictions showed that most TwChis were presumed to be located in the chloroplast, with a few being present in the nucleus and extracellular. The enzymatic activity of TwChi2, a GH19 chitinase, showed that TwChi2 was a member of exochitinase (EC 3.2.1.201) with strong thermal stability (40 °C) and broad substrate adaptability of hydrolyzing bipolymer, 1% and 5% colloidal chitin, α-chitin and β-chitin. Altogether, we analyzed the chitinase gene family and characterized a highly active exochitinase from T. weissflogii, which can catalyze the degradation of both chitin polymers and chitin oligosaccharides. The relevant results lay a foundation for the internal regulation mechanism of chitin metabolism in diatoms and provide a candidate enzyme for the green industrial preparation of high-value chitin oligosaccharides. Full article

The fungus Cordyceps javanica is known for entomopathogenicity and effective in the control of various arthropods. Here, we aimed to reveal the chitinase GH18 gene family expansion through the high throughput sequencing of the genome of C. javanica strain Bd01 isolated from Xylotrechus quadripes larvae. The genome was 34 Mb in size with 9590 protein-coding genes. By comparative genome analysis, it was found that the family GH18 of chitinase genes was expanded in C. javanica Bd01. The phylogenetic analysis of 27 GH18 genes, compared with those from four other species, revealed that the genes could be categorized into three distinct groups based on their conserved domains. Genes within the same cluster exhibited shared protein motifs and orthologous relationships. The molecular mass of these GH18 genes ranged from 14.03 kDa to 81.41 kDa, while their theoretical isoelectric point (pI) values spanned from 4.40 to 7.92. Most chitinases were characterized as extracellular, hydrophilic, and thermostable proteins with a negative charge. Additionally, they demonstrated favorable in vivo half-life stability. A three-dimensional structural model of the GH18 protein was further generated using the SWISS-MODEL server. These findings establish a robust genomic framework elucidating the functional diversity, evolutionary conservation patterns, and mechanistic contributions of virulence-associated genetic determinants. Full article

The chitinase binding domain (ChBD) plays a crucial role in the properties of enzymes. To assess its impact, we cloned a truncated mutant of the chitinase gene CaChi18B from the novel chitinase-producing facultative anaerobic bacterium Chitinilyticum aquatile CSC-1, designated as CaChi18B_ΔChBD_s. The recombinant chitinase was successfully expressed and purified, exhibiting a specific activity of 3.48 U/mg on colloidal chitin, with optimal conditions at 45 °C and pH 6.0, and retaining over 80% activity at temperatures up to 40 °C. Kinetic analysis revealed that the K_m value was 1.159 mg mL⁻¹ and the V_max was 10.37 μM min⁻¹ mg⁻¹. Compared to CaChi18B_ΔChBD₁, which has only the first ChBD truncated at the N-terminus, CaChi18B_ΔChBD_s exhibited minor changes in the optimal temperature and pH, while the K_m and V_max values increased significantly. CaChi18B_ΔChBD_s exhibited tolerance to various metal ions, with K⁺ and NH₄⁺ enhancing activity, while Cu²⁺ significantly inhibited it. Most organic reagents had minimal impact, except for formic acid, which severely reduced activity. The primary hydrolysis product in the initial phase was GlcNAc, contrasting with (GlcNAc)₂ for CaChi18B_ΔChBD₁. These findings indicated that the ChBD influences the enzyme’s K_m, V_max, and product distribution, enhancing our understanding of ChBD’s roles and advancing chitin utilization. Full article

Glycoside hydrolase family 18 (GH18) proteins can hydrolyze the β-1,4-glycosidic bonds of chitin, which is a common structure component of insect exoskeletons and fungal cell walls. In this study, 36 GH18 genes were identified and subjected to bioinformatic analysis based on the genomic data of Glycine max. They were distributed in 16 out of 20 tested soybean chromosomes. According to the amino acid sequences, they can be further divided into five subclades. Class III chitinases (22 members) and class V chitinases (6 members) are the major two subclades. The amino acid size of soybean GH18 proteins ranges from 173 amino acids (aa) to 820 aa and the molecular weight ranges from 19.46 kDa to 91.01 kDa. From an evolutionary perspective, soybean GH18 genes are closely related to Medicago (17 collinear loci with soybean) and Lotus (23 collinear loci with soybean). Promoter analysis revealed that GH18 genes could be induced by environmental stress, hormones, and embryo development. GmGH18-15, GmGH18-24, and GmGH18-33 were screened out due to their nodulation specific expression and further verified by RT-qPCR. These results provide an elaborate reference for the further characterization of specific GH18 genes, especially during nodule formation in soybean. Full article