Plant diseases caused by Pseudomonas syringae pathovars pose a substantial threat to global crop production. While plants produce a range of secondary metabolites as part of their defense response, how bacterial pathogens exploit these compounds to facilitate infection remains poorly understood. Here, we report that P. syringae pv. actinidiae, the causal agent of kiwifruit bacterial canker, senses putrescine (Put), a crucial plant metabolite involved in defense and physiological regulation, via the histidine kinase BvgS. We identify BvgS as a Put receptor in bacteria and show that this perception upregulates the expression of the type III secretion system (T3SS), a major virulence determinant. Binding and virulence assays demonstrate that Put sensing through the periplasmic solute-binding protein (PBPb) domains of BvgS is essential for T3SS activation both in vitro and during plant infection. Modulating Put levels in Actinidia plants, either by genetic reduction or exogenous application, correspondingly alters T3SS activity and bacterial invasion. Evolutionary analysis indicates that the PBPb domain is highly conserved across diverse P. syringae pathovars, suggesting a widespread mechanism for virulence potentiation. This work delineates a signaling pathway by which a phytopathogen co-opts a central host metabolite to enhance expression of its core virulence machinery, thereby increasing infectivity.

Microbial competition serves as a fundamental driver for the evolution of offensive and defensive mechanisms among microorganisms. While it is well established that bacteria utilize specialized secretion systems to deliver both toxic and non-toxic effector proteins into competing cells, thereby directly killing them or modulating cellular events, it remains largely unclear whether bacteria can hijack effector proteins derived from competitors to resolve interspecies conflicts. Here, we demonstrate that Pseudomonas protegens employs a sophisticated defense strategy, hijacking LtaE, a non-cytotoxic effector delivered via the type IV secretion system (T4SS) of non-flagellated Lysobacter enzymogenes, to resolve interbacterial conflict through transcriptional reprogramming. Translocated LtaE neutralizes an uncharacterized antibacterial toxin in P. protegens. Surprisingly, as a countermeasure, P. protegens hijacks LtaE to rewire its host signaling hierarchy, converting it into a motility activation switch. Mechanistically, LtaE directly binds to FleQ, the σ54-dependent master regulator of flagellar biosynthesis, shielding it from inhibitory c-di-guanosine monophosphate (GMP) binding—a universal second messenger whose elevated concentration typically inhibits bacterial motility and promotes biofilm formation. Remarkably, the LtaE-FleQ complex remains stable under high c-di-GMP conditions, overriding sessility signals to derepress flagellar gene expression and trigger escape motility. Biochemical analyses reveal that LtaE broadly targets FleQ homologs across pseudomonads through competitive inhibition of c-di-GMP binding, linking competitor detection to motility activation. Our findings establish a novel bacterial conflict-resolution paradigm, demonstrating how non-cytotoxic effectors act as molecular switches to dynamically reprogram transcriptional networks and enhance phenotypic plasticity.

Bacterial pathogens harbor numerous two-component systems (TCSs) in their genomes, which enable rapid sensing and response to environmental fluctuations, thereby facilitating dynamic adaptation to diverse ecological niches. Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of kiwifruit bacterial canker (KBC), a devastating disease threatening global kiwifruit production. However, the biological function of the metal-responsive TCS CzcSR in Psa remains largely uncharacterized. In this study, we demonstrated that CzcSR plays a crucial role in regulating Psa pathogenicity in the host plant and the hypersensitive response (HR) in the non-host plant. Under zinc ion (Zn2+) stress, Psa exhibited suppressed motility and enhanced oxidative stress tolerance; notably, this phenotype depends on the Zn2+-binding sites of CzcS and the phosphorylation status of CzcR. However, the key virulence factor type III secretion system (T3SS) of Psa is unaffected by Zn2+ stress, and CzcSR-mediated regulation of the T3SS is independent of both the Zn2+-binding sites of CzcS and the phosphorylation status of CzcR. Instead, CzcR controls T3SS expression by binding to the promoter region of hrpR and modulates the c-di-GMP level via interacting with diguanylate cyclase (DGC) PSA_4781. Collectively, our findings expand CzcSR's functional repertoire, highlight TCS complexity, and deepen understanding of TCS versatility—CzcSR integrates Zn2+ signals for canonical regulation of phenotypes (e.g., motility, antioxidant defense) while using a signal-independent mechanism for T3SS control.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), severely threatens the kiwifruit industry. The type III secretion system (T3SS) is a key virulence factor in Psa, but the regulatory mechanisms remain poorly understood. Polymyxin B1, the main component of polymyxin B, inhibits T3SS gene expression in Psa, yet its underlying mechanism is unclear. Cyclic diguanosine monophosphate (c-di-GMP), a crucial bacterial second messenger, is synthesized by diguanylate cyclases (DGCs) containing a GGDEF domain. In this study, we identified and characterized PSA_1379 (WspR), a GGDEF domain-containing protein in Psa. Biochemical assays demonstrated that WspR exhibits DGC activity. Virulence assays showed that WspR negatively regulates Psa virulence. RT-qPCR analyses revealed that polymyxin B induces wspR expression. Additionally, polymyxin B upregulates intracellular c-di-GMP levels and inhibits the expression of T3SS genes through WspR. Bacterial two-hybrid and GST pull-down assays confirmed that WspR interacts with the transcription factor PsrA. Both WspR and c-di-GMP inhibit the binding of PsrA to the promoter of the T3SS master regulator hrpL, thereby suppressing PsrA-mediated transcriptional activation of hrpL and ultimately repressing T3SS gene expression. This study provides new insights into Psa virulence regulation and suggests potential targets for KBC control through the WspR-c-di-GMP pathway.

Bacterial and fungal diseases cause significant losses in horticultural crops, and biocontrol using beneficial microorganisms offers a sustainable alternative to chemical pesticides. In this study, a novel Pseudomonas strain D3 was isolated from Actinidiae rhizosphere. D3 exhibited strong antibacterial activity in LB medium but showed no activity against fungi or oomycetes. However, when cultured in KIDO medium, it demonstrated potent antifungal activity. Phylogenetic analysis based on 16S rRNA gene showed that D3 was most closely related to Pseudomonas mosselii CIP_105259T, while whole-genome sequencing revealed ANI values below 95% with eight known P. mosselii strains. Digital DNA-DNA hybridization (dDDH) further confirmed its genomic distinctiveness, with the highest dDDH value (58.2%) against the type strain P. mosselii DSM 17497T, well below the 70% species delineation threshold, supporting D3 as a novel Pseudomonas species. Functional validation via targeted gene knockout revealed a dichotomy in the antagonistic mechanisms of D3. Knockout of individual biosynthetic gene clusters (BGCs) only partially reduced antibacterial activity against Pseudomonas syringae pv. actinidiae, indicating that multiple BGCs contribute to this activity in a partially redundant manner. In contrast, disruption of a specific lipopeptide synthase cluster completely abolished antifungal activity against Valsa mali. LC-MS/MS analysis confirmed that this lipopeptide was produced exclusively in KIDO medium, consistent with the observed medium-dependent antifungal activity. Detached leaf and twig assays showed that D3 provides strong preventive biocontrol against both pathogens. Collectively, strain D3 employs a dual biocontrol mechanism, combining antibacterial activity mediated by multiple BGCs with lipopeptide-dependent antifungal activity, positioning it as a promising agent for sustainable disease management in horticultural crops.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), severely impacts kiwifruit production. Previous studies show that Psa exhibits enhanced virulence under cool temperatures; however, the underlying regulatory mechanisms remain unclear. Given the crucial role of histidine kinases (HKs) in bacterial responses to environmental signals, bioinformatics analysis predicted a total of 69 HKs in Psa, among which hktS was identified as the key cool-temperature-responsive gene. Structural analysis and co-transcription experiments revealed that HktS and its corresponding response regulator HktR constitute a functional two-component system (TCS). We found that mutations in the key phospho‑related residues of HktS and HktR impair cool temperature sensing and reduce the virulence of Psa. Further research demonstrated that HktR directly interacts with the transcription factor RpoD and binds to a conserved motif in the promoter region of hrpRS, thereby activating expression of the type III secretion system (T3SS). Genetic and expression analyses showed that the HktS‑HktR system displays a conserved cool-temperature-responsive expression pattern across the tested strains and is highly conserved within the genus Pseudomonas. Thus, we identified a histidine kinase essential for Psa virulence under cool temperatures and elucidated the underlying molecular mechanism. Our findings provide a critical theoretical basis and potential molecular targets for developing novel control strategies for KBC.

Plants deploy diverse secondary metabolites for chemical defense against pathogens, and in response, phytopathogens have evolved elaborate counterstrategies to subvert host immunity. In this study, we demonstrate that Pseudomonas syringae pv actinidiae strain M228 (Psa_M228)─the causal agent of kiwifruit bacterial canker (KBC)─employs a dual-functional system to sense and degrade host-derived p-coumaric acid (p-CA), thereby neutralizing the host's chemical defense. Specifically, the kiwifruit host plant produces p-CA, which binds to histidine kinase CasK of Psa_M228's two-component signaling system CasKR, inhibiting response regulator CasR phosphorylation. This reduces CasR binding to the promoter region of fleQ, downregulating hrpL expression─a master regulator of Type III secretion system (T3SS), ultimately attenuating virulence. For counter-defense, Psa_M228 utilizes the HcaR (hydroxycinnamic acid regulator) receptor and hca gene cluster (encoding p-CA-degrading enzymes) to catabolize p-CA. This adaptation helps Psa_M228 evade plant immunity and restore virulence, revealing a host-pathogen arms race.

Kiwifruit bacterial canker, caused by Pseudomonas syringae pv. actinidiae (Psa), is a significant threat to the kiwifruit industry. The two-component signaling systems (TCSs) play a crucial role in regulating the virulence of P. syringae, yet their specific function in Psa remains largely unclear. In this study, we found that disrupting the TCS RegAB (encoded by Psa_802/Psa_803) resulted in a notable increase in the virulence of P. syringae pv. actinidiae M228 (Psa M228) in host plant and hypersensitive reaction (HR) in nonhost plant. Through comparative transcriptome analysis of the Psa M228 wild-type strain and the regA mutant, we identified the pivotal role of RegAB in controlling various physiological pathways, including the type III secretion system (T3SS), a key determinant of Psa virulence. Additionally, we discovered that the RegA has binding sites in the promoter region of the hrpR/S, and the transcriptional level of the hrpR and other T3SS-related genes increased in the regA deletion strain relative to the Psa M228 wild-type. The DNA-binding affinity of RegA, and therefore the repressor function, is enhanced by its phosphorylation. Our findings unveil the function of TCS RegAB and the regulatory mechanism of T3SS by RegAB in Psa, highlighting the diverse functions of the RegAB system.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), threatens global kiwifruit production. Traditional control methods face challenges like bacterial resistance and environmental issues. In this study, four lytic phages (pSM43, pGZ41, pWA51, and pSO21) were isolated and characterized using Psa M228 as the host bacterium. Notably, the phage pGZ41 represents a novel phylogenetic lineage, and the four-phage cocktail demonstrates significant advantages over previously reported single phages or mixtures in terms of lytic spectrum and resistance management. These phages exhibit distinct structural features and biological properties. Genomic sequencing classified them as double-stranded DNA viruses with genome sizes spanning 38,130 to 100,813 base pairs (bp), encoding 91 to 309 putative opening frames. The complete genome sequences have been deposited in GenBank under accession numbers PX673947 (pSM43), PX673946 (pGZ41), PX673948 (pWA51), and PX673949 (pSO21). The phage cocktail has a significant inhibitory effect on the growth of Psa M228 in vitro in Arabidopsis thaliana and in kiwifruit leaf discs. In vitro tests demonstrated that phage cocktails could effectively suppress bacterial growth and delay the emergence of resistant strains within a short period. In A. thaliana, phages exhibited strong antibacterial capabilities, reducing bacterial load by 4.92 log CFU/g in the treatment group and 4.33 log CFU/g in the prevention group compared with the infected control group. In kiwifruit leaf disc assays, the prevention group treated with phage cocktails exhibited superior efficacy, reducing lesion areas by three to five times compared with the treatment group. The significant efficacy in plant models, combined with the high environmental stability of the phages (particularly pGZ41), underscores the strong potential of this phage cocktail as a practical, sustainable, and environmentally friendly biocontrol agent for integrated management of kiwifruit canker in orchard settings. This multilevel validation suggests these phages as promising biocontrol agents for controlling kiwifruit canker caused by Psa.

Animal communication within a community is essential for their survival and reproduction. This phenomenon is not restricted to animals but is also prevalent in prokaryotes, which employ quorum sensing (QS) mechanisms for communication and behavior. Despite their importance, cell-cell communication in prokaryotes has not been cataloged in detail. Therefore, we developed a comprehensive map of cell-cell microbial communication by analyzing 15,297 prokaryotic genomes, thereby expanding the scope of the AI-2 signal in the microbiome. We showed that LsrB receptors are found in 15 bacterial phyla and can regulate the expression of genes involved in the biosynthesis of siderophore group nonribosomal peptides and biofilm formation via LsrB in Streptomyces coelicolor. We also conducted an international prospective study of microbial communication models across distinct habitats. These findings highlight the importance of microbial communication and will enable comprehensive studies of large-scale microbial communities, greatly expanding our understanding of AI-2 in the microbial consortium.

Type VII secretion systems (T7SS) are increasingly recognized as pivotal for bacterial adaptation across both environmental and host-associated niches in Gram-positive bacteria. Although T7SS has been reported to contribute to iron acquisition, the possibility of an active, more targeted iron uptake mechanism remains underexplored. Here, we reveal a distinct, active T7SS-mediated iron import mechanism in Corynebacterium glutamicum. We show that T7SS expression is induced under iron limitation and oxidative stress conditions and is tightly regulated by the ferric uptake regulator (Fur) to benefit bacterial survival. Surprisingly, this iron uptake pathway relies on the T7SS-secreted effector ExsI, an iron-binding protein that collaborates with the membrane receptor ExiR to facilitate iron uptake into the cytoplasm. This ExsI-ExiR-mediated active iron acquisition mechanism enhances bacterial oxidative stress resistance and confers a competitive advantage in iron-limited environments. Furthermore, we show that ExsI homologs in Mycobacterium smegmatis circumvent calprotectin-mediated nutritional immunity, extending the relevance of this mechanism to host-pathogen interactions. Taken together, our data demonstrate a key role for T7SS in orchestrating active iron uptake, oxidative stress resilience, competitive fitness, and evasion of host nutritional immunity, highlighting its significant role in bacterial physiology and host-pathogen interactions.IMPORTANCEType VII secretion systems (T7SS) are increasingly recognized as an indispensable secretion system for Gram-positive bacteria, mediating processes vital for bacterial survival and pathogenesis. This work reveals a previously unrecognized mode of active iron acquisition mediated by T7SS, which not only boosts oxidative stress resistance in Corynebacterium glutamicum but also provides a competitive edge under nutrient-limited conditions. ExsI homologs in Mycobacterium smegmatis overcome calprotectin-mediated iron withholding, suggesting that T7SS-driven iron acquisition extends to immune evasion. These uncovered previously unreported functions of T7SS emphasize the indispensable importance of T7SS in bacterial physiology, enhancing our understanding of T7SS.

Plant domestication involved prolonged artificial selection that progressively adapted plants to human agricultural practices. This process significantly modified both the genetic diversity and the phenotypic and genotypic characteristics of the domesticated plants, resulting in traits that markedly differ from those of their wild ancestors. At the same time, rhizosphere microorganisms, the second largest gene pool of plants, were also inadvertently altered by domestication through changes in root secretions, nutrient uptake or plant defence responses. In this review, we discuss the effects of domestication on plant rhizosphere microbiota and how plants and microbes interact and co-evolve during domestication. The effects of these changes are poorly understood and the subject of active ongoing research. The expected knowledge will help to exploit specific microbial communities for the improvement of plant traits and develop microbial-based management strategies that can be used instead of chemicals to increase plant productivity, reduce environmental pollution and promote the sustainable development of agriculture as a part of the second Green Revolution.

Dehydration-responsive element-binding (DREB) transcription factors associated with abiotic stress responses. However, an understanding of the DREB gene family and its functions in drought tolerance in licorice (Glycyrrhiza uralensis) is limited. In this study, 79 GuDREB genes were identified across the licorice genome and divided into six major groups. In addition, we provided information on the phylogenetic relationships, gene structures, conserved motifs, collinear relationships and cis-regulatory elements of GuDREBs. Bioinformatical and gene expression pattern analysis showed that the expression of the GuDREB35 of the A5 group was considerably induced by drought stress. Overexpression of GuDREB35 significantly enhanced drought tolerance and promoted flavonoid accumulation in licorice. Conversely, GuDREB35-RNAi plants exhibit significantly reduced drought resistance and a significant decrease in flavonoid levels. Transcriptomic analysis revealed that the overexpression of GuDREB35 up-regulated the expression of genes involved in antioxidant defense and flavonoid biosynthesis. Protein-DNA interaction studies further confirmed that GuDREB35 directly bound to the promoters of GuBGLU12 and GuOMT1, which are two enzymes in the flavonoid synthesis pathway. Our research demonstrates that GuDREB35 enhances drought stress tolerance by activating antioxidant defense and flavonoid biosynthesis pathways, providing a theoretical foundation for understanding the molecular mechanisms of drought tolerance and developing drought-resistant licorice varieties.

As an important physiological indicator, wheat canopy temperature (CT) can be observed after flowering in an attempt to predict wheat yield and quality. However, the relationship between CT and wheat yield and quality is not clear. In this study, the CT, photosynthetic rate (Pn), filling rate, wheat yield, and wheat quality of 68 wheat lines were measured, in an attempt to establish a connection between CT and yield and quality and accelerate the selection of new varieties. This experiment used an infrared imaging camera to measure the CT of wheat materials planted in the field in 2022. Twenty materials with significant temperature differences were selected for planting in 2023. By comparing the temperature trends in 2022 and 2023, it is believed that materials 4 and 13 were cold-type materials, while materials 3 and 11 were warm-type materials. The main grain filling period of cold-type materials occurs in the middle and late stages of the grain filling period and the Pn and the thousand-grain weights of cold-type materials were higher than those of warm-type materials. Similarly, under continuous rainy conditions, cold-type materials had a higher protein and wet gluten contents, while warm-type materials had higher sedimentation values and shorter formation times.

Plants and their associated microbiomes are impacted by environmental factors that shape their interactions over time, but long-term trends in microbial community dynamics are not well characterized. We identified the seasonal and long-term population dynamics of root-associated bacterial communities over 8 years in monocropped wheat grown in adjacent dryland and irrigated plots in the low-precipitation region of Washington State. Spring wheat plants were sampled at various times during the growing season over 8 years, and rhizosphere and endosphere communities were characterized using 16S rRNA amplicon sequencing. Analyses throughout the first 3 years revealed genera with distinct annual periodicity in response to growing season conditions. Bacterial richness and diversity were significantly greater in irrigated than in dryland wheat and in the rhizosphere than in the endosphere, apparently driven by the physiological state of the root and root exudates and/or by soil water. Over 8 years, copiotrophic Proteobacteria and Bacteroidetes ( Pseudomonas, Variovorax, Chryseobacterium) maintained stable populations, whereas Actinobacteria decreased in abundance independent of irrigation. Populations of some Bacteroidetes and Proteobacteria ( Mucilaginibacter, Sphingomonas, Massilia, Burkholderia) persisted or increased in relative abundance in the dryland rhizosphere, whereas others ( Rhizobium, Acidovorax, Terrimonas, Hyphomicrobium, Bdellovibrio) increased under irrigation. In contrast, endosphere taxa, including Actinobacteria, declined in relative abundance regardless of irrigation, indicating that the maturing host, and not water, is the main driver of these populations. Our results provide insight into the long-term dynamics of bacterial communities of wheat under contrasting soil water conditions and guide future efforts to improve crop performance under drought conditions. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2025.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), poses a severe threat to the global kiwifruit industry, highlighting the urgent need to elucidate its pathogenic mechanisms. Cyclic diguanylate monophosphate (c-di-GMP) is a bacterial second messenger synthesized by GGDEF domain-containing diguanylate cyclases and degraded by EAL or HD-GYP domain-containing phosphodiesterases. In this study, we characterized PSA_2989, a protein containing both GGDEF and EAL domains, hereafter referred to as DcvP (Diguanylate cyclase regulating virulence in Psa). Biochemical assays demonstrated that DcvP exhibits both DGC and PDE activities in vitro, with DGC activity being more prominent in vivo. Deletion of dcvP enhanced the virulence of Psa on kiwifruit leaves. Transcriptomic and RT-qPCR analyses revealed that DcvP suppresses the expression of type III secretion system (T3SS) genes, flagellar biosynthesis genes, and catalase genes, thereby reducing virulence, motility, and oxidative stress tolerance, primarily through its GGDEF domain. Furthermore, under microaerobic conditions, the expression of dcvP was significantly upregulated, accompanied by increased intracellular c-di-GMP levels and repression of T3SS genes. These results identify DcvP as a negative regulator of Psa virulence through DGC activity and also as being involved in the environmental oxygen response. This work provides new insights into the pathogenic mechanisms of Psa and highlights DcvP as a potential target for KBC control.

Pseudomonas syringae pv. actinidiae (Psa) is a significant pathogenic bacterium affecting the kiwifruit industry. This study investigated the target sites of streptothricin-F (ST-F), produced by Streptomyces lavendulae gCLA4. The inhibition of ST-F on Psa was examined by the microscopic structural differences of Psa before and after treatment with ST-F, as well as the interaction between ST-F and cell division-related proteins. The results revealed filamentation of Psa after ST-F treatment, and fluorescence microscopy showed that ST-F inhibited the formation of the Z-ring composed of FtsZ protein. In vitro experiments and molecular docking demonstrated that ST-F can bind to FtsZ with a binding energy of 0.4 μM and inhibit FtsZ's GTP-dependent polymerization reaction. In addition, ST-F does not exert inhibitory effects on cell division in Psa strains overexpressing ftsZ. In conclusion, FtsZ is one of the target sites for ST-F inhibition of Psa, highlighting its potential as a therapeutic target for controlling Psa-induced kiwifruit bacterial canker.

Within the realm of Gram-negative bacteria, bacteriocins are secreted almost everywhere, and the most representative are colicin and pyocin, which are secreted by Escherichia coli and Pseudomonas aeruginosa, respectively. Signal peptides at the amino terminus of bacteriocins or ABC transporters can secrete bacteriocins, which then enter bacteria through cell membrane receptors and exert toxicity. In general, the bactericidal spectrum is usually narrow, killing only the kin or closely related species. Our previous research indicates that YPK_0952 is an effector of the third Type VI secretion system (T6SS-3) in Yersinia pseudotuberculosis. Next, we sought to determine its identity and characterize its toxicity. We found that YPK_0952 (a pyocin-like effector) can achieve intra-species and inter-species competitive advantages through both contact-dependent and contact-independent mechanisms mediated by the T6SS-3 while enhancing the intestinal colonization capacity of Y. pseudotuberculosis. We further identified YPK_0952 as a DNase dependent on Mg2+, Ni2+, Mn2+, and Co2+ bivalent metal ions, and the homologous immune protein YPK_0953 can inhibit its activity. In summary, YPK_0952 exerts toxicity by degrading nucleic acids from competing cells, and YPK_0953 prevents self-attack in Y. pseudotuberculosis. IMPORTANCE Bacteriocins secreted by Gram-negative bacteria generally enter cells through specific interactions on the cell surface, resulting in a narrow bactericidal spectrum. First, we identified a new pyocin-like effector protein, YPK_0952, in the third Type VI secretion system (T6SS-3) of Yersinia pseudotuberculosis. YPK_0952 is secreted by T6SS-3 and can exert DNase activity through contact-dependent and contact-independent entry into nearby cells of the same and other species (e.g., Escherichia coli) to help Y. pseudotuberculosis to exert a competitive advantage and promote intestinal colonization. This discovery lays the foundation for an in-depth study of the different effector protein types within the T6SS and their complexity in competing interactions. At the same time, this study provides a new development for the toolbox of toxin/immune pairs for studying Gram-negative bacteriocin translocation.

The type VI secretion system (T6SS) is a bacterial weapon capable of delivering antibacterial effectors to kill competing cells for interference competition, as well as secreting metal ion scavenging effectors to acquire essential micronutrients for exploitation competition. However, no T6SS effectors that can mediate both interference competition and exploitation competition have been reported. In this study, we identified a unique T6SS-1 effector in Yersinia pseudotuberculosis named TepC, which plays versatile roles in microbial communities. First, secreted TepC acts as a proteinaceous siderophore that binds to iron and mediates exploitative competition. Additionally, we discovered that TepC has DNase activity, which gives it both contact-dependent and contact-independent interference competition abilities. In conditions where iron is limited, the iron-loaded TepC is taken up by target cells expressing the outer membrane receptor TdsR. For kin cells encoding the cognate immunity protein TipC, TepC facilitates iron acquisition, and its toxic effects are neutralized. On the other hand, nonkin cells lacking TipC are enticed to uptake TepC and are killed by its DNase activity. Therefore, we have uncovered a T6SS effector, TepC, that functions like a "Trojan horse" by binding to iron ions to provide a valuable resource to kin cells, whereas punishing cheaters that do not produce public goods. This lure-to-kill mechanism, mediated by a bifunctional T6SS effector, may offer new insights into the molecular mechanisms that maintain stability in microbial communities.

The optimization of irrigation scheduling presents an effective methodology for augmenting crop yields and enhancing water utilization efficiency. Nonetheless, a comprehensive understanding of the intricate mechanisms through which this strategy influences crop growth and yield formation is yet to be fully understood. In this study, a field experiment was conducted during the winter wheat cultivation period from 2018 to 2020 on two wheat cultivars: JM418, known for its drought tolerance, and SX828, known for its drought sensitivity. These treatments were subjected to four distinct irrigation schedules and two sowing stages. The timing of irrigation was specifically designed to coincide with the visibility of the 3rd, 4th, 5th, and 6th leaves for normal and postponed sowing. Our findings revealed that commencing irrigation at the stage when the 4th leaf becomes visible serves as an advantageous strategy for deficit irrigation. This approach significantly amplified winter wheat yield by 6.96-54.09 % and improved water use efficiency by 9.88-47.62 %. Quantitative analysis of source ability parameters demonstrated that postponed irrigation adversely affected the mean leaf area index (MLAI), total leaf area duration (TLAD), and biomass at maturity (BAM). Furthermore, an increase in mean net assimilation rate (MEAR) and harvest index (HI) was noted during the delayed irrigation phase when the 4th leaf was visible. The highest spike count per hectare was observed when irrigation was executed at the 4th leaf visibility stage, with an average increase of 13.98 %. Conversely, with a postponed irrigation schedule, the mean count of grain number per spike decreased by 2.47, while the 1000-grain weight saw an increase of 1.65 g. Higher sink capacity was obtained with irrigation when the 3rd and 4th leaves were visible. Despite this, the grain-leaf ratios when irrigated at the 4th, 5th, and 6th leaf visibility stages were significantly higher than those irrigated at the 3rd leaf visibility stage. In conclusion, our findings elucidate that the irrigation strategy coinciding with the 4th leaf visibility stage exhibits superior grain yield and water use efficiency (WUE) stability. This can be attributed to the enhanced harvest index, effective spike number per unit area, and biomass accumulation. Concurrently, the number of grains per panicle and the 1000-grain weight were relatively balanced. Our research offers novel insights into the mechanism of source-sink regulation in crops under deficit irrigation conditions and lays the groundwork for the development of precise and efficient irrigation strategies.