[Objective] To investigate the interactions between coral-associated Symbiodiniaceae and bacteria in mediating heat stress adaptation of corals. [Methods] Using Pocillopora damicornis harbouring distinct Symbiodiniaceae clades, we performed a laboratory-controlled heat stress simulation experiment to examine the dynamics of symbiotic bacterial community shifts via 16S rRNA gene amplicon sequencing. [Results] Bacterial alpha diversity exhibited a transient increase during the initial stress, followed by a significant decrease under prolonged stress, in P. damicornis harbouring clade C (Cladocopium spp.) or clade D (Durusdinium spp.) algal symbionts (i.e., PdC versus PdD holobionts). Compared with PdD, PdC demonstrated enhanced bacterial community shifts, alongside progressively diminished network stability and complexity with prolonged heat stress. Analysis of bacterial abundance at the class level revealed divergent trajectories of the two holobionts, with the abundance of Alphaproteobacteria increasing in both PdC and PdD, whereas that of Cyanobacteriota increasing in PdC but decreasing in PdD over the course of the experiment. During the later stage of heat stress, Cladocopium spp. in PdC showed increased sensitivity, coinciding with the enrichment of potentially opportunistic pathogens, whereas Durusdinium spp. in PdD were thermotolerant, coinciding with elevated abundance of bacteria possibly involved in photosynthesis, quorum sensing, calcification, and ABC transport. [Conclusion] These findings suggest that different clades of Symbiodiniaceae might interact with bacteria to differentially regulate the P. damicornis response to heat stress. Thermal sensitive Cladocopium spp., combined with the proliferation of potential opportunistic pathogens, may exacerbate the risk of thermal bleaching in PdC, whereas resilience could be strengthened in PdD via thermotolerant Durusdinium spp. coordinating with beneficial bacteria with supportive metabolic potential (e.g., photosynthesis, calcification, and quorum sensing). This algal-bacterial interaction mode provides critical insights into the microbially-mediated thermal bleaching mechanisms and an important reference for the practice of reef restoration in the context of global climate change.

[Objective] Aluminum (Al) toxicity in acidic soils severely inhibits plant growth by inducing oxidative stress. Ectomycorrhizal fungus (ECMF) can enhance host plant Al tolerance, but the underlying physiological mechanisms, particularly in fine roots, are not fully understood. This study investigates how ECMF colonization mitigates Al toxicity by modulating the antioxidant physiology of plants, with an aim in applying ECMF for the ecological restoration of Al-contaminated acidic soils. [Methods] Pinus massoniana seedlings were inoculated with Lactarius deliciosus 2 or Pisolithustinctorius 715, with non-ectomycorrhizal seedlings as the control. After a 6-month exposure to 0.0 mmol/L or 1.0 mmol/L Al³⁺, we assessed seedling biomass, fine root morphology, plasma membrane permeability, reactive oxygen species (ROS) levels, antioxidant enzyme activities, and osmoregulatory substance content. [Results] Under Al stress, inoculation with either L. deliciosus 2 or P. tinctorius 715 significantly promoted seedling growth and fine root development. The inoculated seedlings exhibited 1.26-1.33 folds greater biomass and 2.25-3.99 folds increases in the total root length, root surface area, root volume, and root tip number compared to the non-inoculated control. The ECMF inoculation also significantly reduced the accumulation of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline, and soluble proteins in fine roots. Furthermore, inoculation with L. deliciosus 2 resulted in significantly higher root surface area and root volume, along with greater peroxidase (POD) and catalase (CAT) activities and a more pronounced reduction in proline content in fine roots, compared to inoculation with P. tinctorius 715. [Conclusion] Our findings demonstrate that ECMF inoculation alleviates Al stress in P. massoniana seedlings by promoting fine root development, bolstering the antioxidant system (notably through increased POD and CAT activities), reducing H₂O₂ accumulation, preserving plasma membrane integrity, and decreasing the synthesis of osmoregulatory substances. The superior performance of L. deliciosus 2 highlights its potential for its application in the ecological restoration of Al-contaminated acidic soils.

[Objective] Kiwifruit bacterial canker (KBC), caused by Pseudomonassyringae pv. actinidiae (Psa), has become the primary bottleneck restricting the sustainable development of the kiwifruit industry in China, highlighting an urgent need for eco-friendly and residue-free biocontrol strategies. [Methods] The kiwifruit variety ‘Hongyang’ was used to systematically evaluate the biocontrol efficacy of Bacillus pumilus H-46 through leaf disc and shoot inoculation assays. The active components were fractionated into three groups (small-molecule metabolites, proteins, and polysaccharides) via sequential extraction, with the major bioactive fraction identified through antimicrobial activity and disease control assessments. An integrated approach combining histochemical staining, antioxidant enzyme activity assays, and RT-qPCR of defense-related genes was employed to elucidate the mechanism of induced systemic resistance (ISR). Furthermore, pathogen migration and colonization assays were conducted to evaluate the inhibitory effects of the active components against Psa. [Results] B. pumilus H-46 showed excellent control effect against KBC, with the disease control efficacy of 86.54% in leaf disc assays. Its main active components (small-molecule metabolites, fraction A) achieved the control efficacy of 88.16% against KBC through non-antimicrobial mechanisms. The mechanisms included triggering early H₂O₂ accumulation and callose deposition, significantly increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, and activating the expression of key genes (AcMYC2, AcAOC, AcERF2, and AcEIN3) in jasmonicacid (JA) and ethylene (ET) signaling pathways to activate ISR. Consequently, the disease resistance of kiwifruit was enhanced, resulting in a reduction of 37.8% in Psa migration distance in leaf veins and a decrease of 96.6% in colonization ability. [Conclusion] Our findings demonstrate that the small-molecule metabolites (fraction A) of B. pumilus H-46 activates JA/ET-mediated ISR via non-antimicrobial mechanisms, offering a sustainable solution for the control against KBC and establishing a prototype for next-generation plant immunity activators in crop protection.

In natural soils, phosphorus predominantly exists in stable forms such as chelated inorganic phosphorus, resulting in low levels of available phosphorus. To cope with phosphorus limitation, woody plants typically form symbiotic associations with ectomycorrhizal fungi (ECMF) to enhance phosphorus acquisition. Studies have indicated that ECMF exhibit limited capacity to directly solubilize chelated inorganic phosphorus. However, they can recruit phosphate-solubilizing bacteria in the hyphosphere by releasing specific compounds, thereby facilitating the desorption of chelated inorganic phosphorus. Nevertheless, comprehensive reviews analyzing the role of plant-ECMF-bacteria tripartite systems in phosphorus cycling remain scarce. This article introduces the conceptual framework of plant-ECMF-bacteria tripartite systems, elucidates the physiological, biochemical, and molecular mechanisms underlying phosphorus cycling among ECMF, mycorrhiza helper bacteria, and host plants, and discusses future research directions for optimizing plant phosphorus acquisition through the tripartite systems.

Chitin is the second largest renewable resource only after cellulose on Earth. Chitinases are the key enzymes for degrading chitin. Chitinases of the glycoside hydrolase family 19 (GH19) mainly exist in higher plants. In recent years, microbial GH19 chitinases have been widely discovered. This paper reviews the research progress in microbial GH19 chitinases regarding their distribution, structures, enzymatic properties, and applications and prospects the research directions in the future.

Numb-associated kinases (NAKs) are a family of evolutionarily conserved serine/threonine kinases, encompassing adaptor-associated kinase 1 (AAK1), cyclin G-associated kinase (GAK), bone morphogenetic protein 2-inducible kinase (BMP2K), and serine/threonine kinase 16 (STK16). NAKs are widely involved in various physiological processes, such as endocytosis, intracellular transport, cell differentiation, autophagy, and signal transduction. In recent years, studies have shown that NAKs play a key role in different life cycle stages including virus entry, assembly, release, and immune escape of various viruses. Furthermore, small-molecule inhibitors targeting NAKs have been applied in clinical research and treatment of related physiological or viral infectious diseases. This article systematically reviews the primary physiological functions of NAKs and their roles in viral infection, aiming to provide a theoretical foundation for elucidating the pathogenic mechanisms of viruses and developing novel therapeutic drugs targeting NAKs.

Antibodies serve as critical effector molecules in mediating vaccine-induced protection. While antibody-mediated immunity has traditionally been attributed primarily to neutralization, where the fragment antigen-binding (Fab) domain blocks viral entry by preventing the interaction between viruses and host cells, accumulating evidence underscores the pivotal role of the crystallizable fragment (Fc) domain in orchestrating broader immune responses. By interacting with Fc receptors or complement receptors on effector cells such as natural killer cells, macrophages, neutrophils, and dendritic cells, the Fc domain activates multiple innate immune pathways and elicits a spectrum of non-neutralizing antiviral effector functions. These include antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent complement deposition (ADCD), and complement-dependent cytotoxicity (CDC). Although the evaluation of Fc-mediated functions is more complex than the measurement of neutralizing antibody titers, the contribution of such functions to vaccine efficacy is increasingly recognized. This review provides a comprehensive overview of Fc-mediated immune effector mechanisms, highlights their critical roles in antiviral vaccine-induced protection, and summarizes recent advances in Fc function assays, with the aim of supporting the rational design and immunogenicity evaluation of next-generation viral vaccines.

The mandarin fish (Siniperca chuatsi) is one of the most economically important cultured fish species in Asian countries. With the expansion of artificial farming, infectious diseases have become a major threat to the mandarin fish farming industry, posing a challenge to its sustainable development. Siniperca chuatsi rhabdovirus (SCRV) is a major pathogen infecting this fish species. In recent years, substantial progress has been made in the research on SCRV, yet no comprehensive review is currently available. This paper summarizes and discusses the research advances in SCRV, including viral characteristics, virus rescue, host-virus interactions, and prevention strategies, while also analyzing the current challenges in this field.

The gut microbiota maintains a close dialogue with the host’s immune system, being capable of influencing immune responses through various pathways. It has been extensively documented that synchronous regulation of the gut microbiota and the host immune response exerts immunoenhancing, anti-inflammatory, and gut homeostasis-maintaining effects. By systematically reviewing the relevant literature published in the past three years, this article first elaborates on the interactions between the gut microbiota and the host’s immunity via multiple routes. It further summarizes recent studies on natural products that exert immunomodulatory functions (encompassing both immunoenhancing and anti-inflammatory actions) through gut microbiota pathways. Regarding immune dysregulation diseases, this review further elucidates how natural products achieve precise regulation of the host immune function by optimizing the gut microbiota structure, regulating microbiota-immune signaling pathways (e.g., NF-κB, TLR, and MAPK), maintaining intestinal barrier homeostasis, and intervening in microbiota-derived metabolites (such as short-chain fatty acids and tryptophan-indole derivatives). Additionally, this article discusses the process by which the gut microbiota enhances the immunomodulatory effects of natural products through metabolic conversion and biotransformation of natural products into highly active secondary metabolites. The immunoregulatory effects of natural products through the gut microbiota may become a potential therapeutic strategy for immune-related disorders.

Agrobacteriumtumefaciens, a classic model organism for plant-microbe interaction research, is a valuable transgenic tool for plants. Phenolic acids secreted by plants after injury can affect the infection of the host by A. tumefaciens. Objective This study investigated the transcription factor PcaR of A. tumefaciens regarding its effects on the metabolism of simple phenolic acids, regulation of the target gene, and effect on the bacterial tumorigenicity in host plants. Methods The A. tumefaciens strain with atu4546 knockout (Δatu4546) and the complement strain C-Δatu4546 were constructed via the suicide plasmid pEX18Km and the plasmid pUCA19 with a strong promoter, respectively. Both Δatu4546 and C-Δatu4546 were tested for growth with p-hydroxybenzoic acid or protocatechuic acid as the sole carbon source and tumorigenicity on carrot stems and Kalanchoe pinnata leaves. In the wild-type strain C58 and Δatu4546, the reporter gene was in situ inserted into the downstream region of the metabolic target gene atu4549. The regulatory link between atu4546 and the target gene was examined based on the β-galactosidase activity. To investigate the self-regulation of PcaR, we constructed the atu4546 self-promoter reporter plasmid. To identify the binding sites of PcaR, we constructed the upstream promoter region reporter plasmid of the target gene to remove or replace the predicted binding sites and then determined the β-galactosidase activity. Results The knockout of atu4546 did not affect the growth of A. tumefaciens on sucrose, but led to the inability to use p-hydroxybenzoic acid or protocatechuic acid as the sole carbon source. The growth was restored after atu4546 was complemented. The tumor weights of carrot stems and K. pinnata leaves infected by Δatu4546 decreased by 34.90% and 52.58%, respectively, and the number of colonies per 0.1 g tumor decreased by 72.19% and 80.54%, respectively. The knockout of atu4546 led to a 102.04% increase in its own promoter activity, which suggested that atu4546 negatively regulated its own expression. Atu4546 boosted the expression of the atu4547-atu4549 gene cluster, as evidenced by a 74.86% decrease in β-galactosidase activity downstream of the target gene in Δatu4546 compared with that in the wild type. The promoter region sequence alteration experiment identified GTGCGATATATACGAAC as the binding site of PcaR. Conclusion This study shows that the transcription factor PcaR is involved in phenolic acid catabolism, negatively regulates itself and stimulates the transcription of the downstream gene pcaIJF. The binding site of PcaR to the target gene is GTGCGATATACGAAC. The knockout of PcaR attenuates the pathogenicity of A. tumefaciens. This study reveals the dual regulation mechanism in the phenolic acid metabolism-pathogenic signaling pathway and expands the theoretical cognition of plant-microbe interactions.