Molecular plant pathology最新文献

Tung wilt disease, caused by Fusarium oxysporum f. sp. fordiis (Fof-1), poses a serious threat to tung oil tree (Vernicia fordii) production. Fortunately, another native Vernicia species in China, V. montana (woody tung oil tree) exhibits high resistance ability to the pathogen. The resistant and susceptible tung trees provide material for the investigation on the mechanism underlying the resistance to Fusarium wilt disease. Root xylem extracts of resistant V. montana significantly inhibited Fof-1 growth compared with that of susceptible V. fordii. Metabolomic analysis of V. montana root xylem revealed that 13 types of flavonoids increased after Fof-1 infection. Of the 13 flavonoids, antimicrobial assays showed that catechin, (-)-epicatechin and (-)-epigallocatechin exhibited an obvious inhibitory effect on Fof-1 growth. Transcriptomic analysis revealed that several genes with up-regulated expression patterns were also enriched in the flavonoid biosynthesis pathway after Fof-1 infection in V. montana. Among them, the anthocyanidin reductase (ANR) gene is directly involved in the biosynthesis of antimicrobial (-)-epicatechin and (-)-epigallocatechin. Moreover, transgenic V. montana lines overexpressing the VmANR gene elevated eight types of flavonoid concentrations, and silencing VmANR resulted in a substantial reduction in the levels of catechin and myricitrin. The enzyme activity assay in vitro further verified that VmANR catalysed the formation of (-)-epigallocatechin from the substrate cyanidin. This study identifies VmANR as a critical gene to promote biosynthesis of antimicrobial flavonoids in shaping resistance to Fof-1 infection, and offers an effective strategy for breeding Fusarium-resistant tung oil trees.

MicroRNAs (miRNAs) are a class of noncoding RNAs that play important roles in regulating gene expression. They are involved in various biological processes, including plant growth, development, hormone signalling pathways and defence responses. Numerous studies have demonstrated the crucial role of miRNA in modulating plant immunity against various pathogens, including fungi, bacteria, viruses, nematodes and oomycetes. In this review, we synthesise recent advances in defence-related miRNAs in response to pathogens, highlighting their effects on plant-pathogen interactions and their functions in regulating hormone signalling pathways. Additionally, we explore the potential of small RNA-based technology tools in protecting plants from pathogens, including artificial microRNA, synthetic trans-acting small interfering RNA and RNA interference techniques, such as spray-induced gene silencing, host-induced gene silencing and virus-induced gene silencing.

Lipopolysaccharide (LPS) is a critical component of the bacterial outer membrane, which serves as a permeability barrier and site for sensing environmental signals. The structure and functional significance of LPS vary among bacterial species, influencing pathogenic traits. In this study, we aimed to investigate LPS biosynthesis genes in Pectobacterium carotovorum PCC27, the causal agent of bacterial soft rot in vegetable crops, and characterise the effects of their disruptions on virulence. Mutants lacking any LPS component exhibited reduced rotting symptoms on the midrib of kimchi cabbage and antimicrobial resistance, underscoring the importance of an intact LPS for virulence. The absence of O-antigen components did not affect the expression of major virulence factors; however, LPS core defects significantly impaired bacterial multiplication in planta, proteolytic activity and motility, which were progressively suppressed with greater truncations. Complementation analyses revealed that gene overexpression failed to restore these mutant phenotypes to the wild-type levels. Furthermore, western blot-based assembly assays of the type I secretion system demonstrated that LPS core truncation disrupted the outer membrane component PrtF localization. Additionally, the antiterminator factor RfaH was found to activate a large gene cluster directly involved in O-antigen biosynthesis, although it was dispensable for virulence. Together, these findings highlight the critical role of the LPS core in the functional assembly of outer membrane apparatuses, thereby contributing to virulence in P. carotovorum.

Botrytis cinerea is a necrotrophic fungus that infects more than 200 plant species, causing significant economic losses worldwide. Due to its diverse pathogenicity, extensive efforts have been made to unravel its pathogenic mechanisms. However, the function of the effectors underlying B. cinerea virulence remains largely unknown. In this study, we identified an effector BcSCR1 (B. cinerea small cysteine-rich protein 1) and found that it interacts with the transcription factor PFB1 (Pericycle Factor Type-B1) in Arabidopsis thaliana. Ectopic expression of BcSCR1 in plants resulted in decreased resistance to B. cinerea infection, while disruption of BcSCR1 in B. cinerea significantly decreased its aggressiveness toward host plants. In addition, the mutation of PFB1 in Arabidopsis increased resistance of plants to B. cinerea infection. PFB1 directly activated the expression of OPR3 and WRKY33 under normal conditions, while the binding of BcSCR1 to PFB1 repressed its transcriptional activation activity during B. cinerea infection. These findings reveal that B. cinerea employs the effector protein BcSCR1 to promote infection by suppressing the plant's immune defences.

Cell death-inducing proteins (CDIPs) are critical mediators of infection in the necrotrophic pathogen Botrytis cinerea, enabling host colonisation across its broad plant host range. Here, we identified a novel plant CDIP from B. cinerea, BcGH61, that exhibits dual activity: triggering extensive plant cell death while simultaneously promoting host defence responses. Functional analysis demonstrates that its full cell death-inducing capacity requires its apoplastic compartmentalisation, intact glycoside hydrolase activity, two conserved cysteine residues, and specific structural motifs spanning residues 193-240. Notably, this phytotoxic activity operates through a mechanism independent of the canonical immune coreceptors BAK1 and SOBIR1. During pathogenic invasion, bcgh61 demonstrates upregulated expression. While the bcgh61 gene deletion mutant displays no significant developmental defects, it exhibits severely attenuated virulence, establishing BcGH61 as an essential pathogenicity factor. Furthermore, we identified NbHrBP1, a Nicotiana benthamiana hypersensitive response-binding protein, as a direct interactor of BcGH61 during infection, functioning in intracellular immune perception but not in cell death induction. Taken together, our results provide evidence that BcGH61 is a novel critical virulence factor for establishing infection in host plant by its phytotoxic activity and underscore the role of NbHrBP1-based plant surveillance system in recognising fungal secreted proteins as a pivotal defence strategy against necrotrophic pathogens.

Plants detect microbe-associated molecular patterns from pathogens via plasma membrane-localised receptors, which activate multiple signalling cascades that lead to pattern-triggered immunity (PTI). Receptor-like cytoplasmic kinases (RLCKs) are central to plant immune signalling and common targets of pathogen effectors. Here, we conducted a yeast two-hybrid screen between tomato (Solanum lycopersicum) RLCKs and type III secreted effectors conserved in Ralstonia solanacearum Korean isolates. We identified members of the RLCK subfamily IXb, containing an integrated plant U-box (PUB) domain, as interactors of RipV1, an effector containing a novel E3 ligase domain (NEL). We demonstrated that SlRLCK-IXb-1 exhibits E3 ligase activity but lacks detectable kinase activity in vitro. RipV1 trans-ubiquitinates SlRLCK-IXb-1 in vitro and enhances its stability in planta. Virus-induced gene silencing of SlRLCK-IXb homologues in Nicotiana benthamiana revealed their role as negative regulators of early PTI signalling and of RipV1-induced cell death. These findings highlight relevant substrates for an E3 ligase effector and provide insights into the complex modulation of plant defence responses.

Plant pathogens employ a diverse array of effectors to facilitate host colonisation, including evolutionarily conserved core effectors. In this study, we identified MoPce1, a CAP/PR-1 domain-containing protein widely distributed among fungal species, as a key virulence factor in Magnaporthe oryzae. Among 72 putative core effectors (PCEs), MoPce1 was found to be essential for pathogenicity but dispensable for asexual development. It localises to biotrophic interfacial complex (BIC) in invasive hyphae (IHs) and to the cytoplasm in Nicotiana benthamiana leaves and rice protoplasts. Ectopic expression of a signal peptide-deleted variant of MoPCE1 (MoPCE1^Δsp) in rice compromised blast resistance and suppressed the reactive oxygen species (ROS) burst. Notably, MoPce1 lacks the conserved cysteine residues essential for sterol-binding in the CAP domain, suggesting its potential association with a novel ligand. Further investigation revealed that MoPce1 interacts with rice catalase OsCATC, specifically via the C1 fragment (231-360 aa). Disruption of OsCATC (oscatc) enhanced rice blast resistance and triggered a stronger ROS burst. Collectively, our results indicate that MoPce1 targets OsCATC to disrupt ROS homeostasis and suppress host immunity, thereby facilitating infection.

This study compares the ability of the cytokinin (CK) trans-zeatin (tZ) and the CK sugar conjugate 6-(3-methoxybenzylamino)purine-9-arabinoside (BAPA) to induce resistance against the bacterial pathogen Pseudomonas syringae in Arabidopsis thaliana. Treatment with either tZ or BAPA significantly reduced bacterial growth after a later infection. This chemically induced resistance (IR) required the CK receptor AHK3, highlighting its critical role in mediating resistance by tZ and BAPA. This is remarkable as these compounds show either high or no affinity for this CK receptor, respectively. Surprisingly, tZ, but not BAPA, induced the expression of CK response genes, including ARR5, suggesting divergent mechanisms of action. Resistance caused by both compounds was abolished in the npr1 mutant, underpinning the functional relevance of the salicylic acid (SA) signalling pathway. Transcriptomic analysis showed that both BAPA and tZ triggered the expression of distinct sets of genes associated with SA and reactive oxygen species (ROS) but not with jasmonic acid (JA) signalling. BAPA and, to a lesser extent, also tZ activated pattern-triggered immunity (PTI) signalling genes, including genes responsible for PTI signal amplification (PREPIP2) and pathogen-associated molecular pattern (PAMP) signalling (PH1, IDL6). This supported the hypothesis that the PTI pathway mediates the protective effect. Similarities and differences of chemically triggered IR by tZ and BAPA, as well as their potential for application, are discussed.

Grapevine, as an important economic crop around the world, has generally poor disease resistance in planting. Vitis vinifera, in particular, show high susceptibility to grey mould (caused by Botrytis cinerea), which leads to a decline in yield and quality. Existing chemical control methods have limitations, including environmental and resistance issues, so breeding disease-resistant varieties is crucial for sustainable agriculture. In this study, we identified a nuclear membrane-localised R2R3-type MYB transcription factor named VlMYB149 whose expression was significantly upregulated following grey mould infection. Overexpression of VlMYB149 in grapevine and Arabidopsis indicated that it significantly enhances resistance to grey mould, characterised by reduced lesion size and inhibited mycelial expansion. VlMYB149 increased the content of copper and increased the activities of antioxidant enzymes such as catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD). VlMYB149 also directly activated the expression of VlHIPP30, which plays a crucial role in the process of copper transport. Overexpression of VlHIPP30 has been shown to enhance disease resistance by reducing reactive oxygen species (ROS) levels and enhancing copper metabolism. Our findings reveal a novel molecular mechanism model for grapevine resistance to B. cinerea, mediated by the synergistic interaction by copper metabolism and the antioxidant system. This study not only provides crucial genetic resources for breeding disease-resistant crops but also advances our fundamental understanding of plant immunity.

Powdery mildew, caused by Podosphaera aphanis, poses a significant threat to strawberry production, while current chemical controls raise environmental and food safety concerns. In this study, we have identified the key regulatory module, FaMYB63/FvWRKY75-PR10.14, that confers enhanced powdery mildew resistance in transgenic strawberry (Fragaria vesca). FaMYB63, an R2R3-MYB transcription factor, was induced by P. aphanis infection and responsive to the application of defence signalling molecules, including salicylic acid (SA), methyl jasmonate (JA), abscisic acid (ABA), and 1-aminocyclopropane-1-carboxylic acid (ACC). Silencing of FaMYB63 led to reduced SA levels and increased powdery mildew susceptibility, accompanied by suppressed reactive oxygen species (ROS) bursts and down-regulation of PR10.14 expression. Conversely, overexpressing PR10.14 in transgenic lines inhibited P. aphanis spore germination and enhanced ROS accumulation, indicating a dual role in direct pathogen inhibition and hypersensitive response-triggered defence. Yeast one-hybrid, electrophoretic mobility shift assay, β-glucuronidase, and luciferase assays confirmed that FaMYB63 and FvWRKY75 were directly bound to the MYB-binding sites and W-box of the PR10.14 promoter, respectively, and activated its transcription, while WRKY75 negatively regulated the expression of MYB63. PR10.14 exhibited tissue-specific expression, with the highest levels in red-ripening fruits, suggesting a role in developmental-stage-dependent defence. These findings suggest FaMYB63 as an SA-dependent regulator of PR10.14-mediated resistance, bridging hormone signalling and pathogen response. This study provides a molecular target for breeding powdery mildew-resistant strawberry cultivars through genetic engineering approaches, offering an alternative to fungicides for sustainable and environmental disease management in horticultural crops and advances our understanding of MYB- or WRKY-PR10P networks in plant immunity.