Project description:Pseudomonas syringae pv. actinidiae biovar 6 (Psa6) is a causal agent of kiwifruit bacterial canker and is a unique plant pathogenic bacterium, producing two types of phytotoxins, coronatine and phaseolotoxin. We investigated the expression behavior of virulent genes of Psa6 under various culture conditions.
Project description:To study the responses of kiwifruit to Pseudomonas syringae pv. actinidiae, one-year-old potted seeding A. c. var. deliciosa cultivar ‘Jinkui’ and the pandemic Pseudomonas syringae pv. actinidiae bacterial strain JF8 (CCTCC AB2018305) were used for this study. This bacterial strain was originally isolated from A. c. var. chinensis cultivar ‘Jinfeng’ and further characterized . Plants were maintained in an aseptic room, with 95% of relative humidity, have natural light and no further fertilization after their receiving from the nursery. For inoculation, the P. s.pv. actinidiae strain was streaked on nutrient-sucrose agar (NSA) and incubated at 25 °C for 48-h. Ten microliters of a bacterial suspension (1-2×107cfu/mL) prepared in sterile 0.85 % w NaCl were inoculated in the plants chosen for investigation. The bacterial suspension was sprayed to entirety tree. In parallel, control plants were treated in the same way with sterile 0.85 % w NaCl solution. The inoculated and control plants were randomly distributed in the room at 15 ± 3 °C. 24-h after inoculation, ‘Jinkui’ leaves were sampled from the infected and control plants for further analyses. Each sample consisted of the leaves of one tree. Three biological replicates were used for each line.
Project description:Purpose: The outcome of host–pathogen interactions is thought to reflect the offensive and defensive capabilities of both players. When plants interact with Pseudomonas syringae, several well-characterized virulence factors contribute to early bacterial pathogenicity, including the type III secretion system (T3SS), which must be activated by signals from the plant and environment to allow the secretion of virulence effectors. The manner in which these signals regulate T3SS activity is still unclear. Conlusion: the analysis revealed that the perception of plant signals from kiwifruit or tomato extracts anticipates T3SS expression in P. syringae pv. actinidiae compared to apoplast-like conditions
Project description:Purpose: Pseudomonas syringae pv. actinidiae (Psa) is a phytopathogen that causes devastating bacterial canker in kiwifruit. Among five biovars defined by genetic, biochemical and virulence traits, Psa3 is the most aggressive and is responsible for the most recent reported outbreaks, but the molecular basis of its heightened virulence is unclear. A custom P. syringae multi-strain whole-genome microarray platform, encompassing biovars Psa1, Psa2 and Psa3 and the well-established model P. syringae pv. tomato, was used to analyse early bacterial responses to an apoplast-like minimal medium. Conlusion: this work highlighted that diverse early responses to the host apoplast, even among bacteria belonging to the same pathovar, can lead to different virulence strategies and may explain the differing outcomes of infections.
Project description:Pseudomonas syringae pv. actinidiae (Psa) is the potential cause of Kiwifruit Bacterial Canker (KBC) but the factors affecting its pathogenicity in natural setting is less elaborated. Here, we isolated two Psa3 strains, G126 and G282, from Guizhou province`s kiwifruit orchards suffering from KBC disease. Both isolates belonging to Psa-biovar 3 were verified by Psa3-specific primers. Compared to Psa3-G1 positive control strain, G282 exhibited significant reduction of necrotic spots and lesion density during pathogenicity assays on kiwifruit leaf discs and branches, while G126 was unable to show any disease phenotype. Similarly, no induction of hypersensitive response in tobacco plants as well as significantly reduced promoter’s activities of hrpA, hrpR/S/L of type III secretion system (T3SS) cascade suggested that both strains are defective in functional T3SS-dependent phenotypes. Genomic sequencing of these strains revealed that T3SS pathway of G126 was defective due to a single-nucleotide polymorphism variation in hrpR gene, while G282 was entirely deprived of T6SS to potentially transmit T3SS effectors. In addition, transcriptomic analysis of GO and KEGG pathways revealed several key aspects related to the secretion system, protein transport and signal transduction being widely affected. This study advances our understanding to the genetic basis of these non-pathogenic and partial pathogenic isolates, and the functional interdependencies between secretion systems (T3SS, T6SS) and metabolic or motility-related pathways, showcasing how genetic mutations lead to widespread physiological changes will provide insights into virulence evolution, the identification of pathogenic determinants, and the development of biocontrol strategies against Psa.
Project description:A ChIP-seq assay was performed to identify the regulons of an ompR-like transcription factor (gene name: 13375, GenBank: AYL80818.1) in Pseudomonas syringae pv. actinidiae. An 13375-overexpressing mutant G1-OE13375, which constitutively express C-terminally Myc-tagged ompR-like gene in the 13375-deletion mutant G1Δ13375, was used in this study. The bacterial cells were cultured either in nutrition-rich KB medium or hrp-derepressing medium (HDM) at 25 C for 24 hours. A PierceTM Magnetic ChIP Kit (Cat. #: 26157, Thermo Fisher Scientific) and a ChIP-grade Myc-Tag Monoclonal Antibody (Myc.A7, Cat. #: MA121316, Thermo Fisher Scientific) were used for sample pretreatment and immunoprecipitation.
Project description:Purpose: Microarray technologies provide a unique opportunity to deeply investigate bacterial molecular responses to treatments. Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of the bacterial canker of kiwifruit causing severe economic losses worldwide. At present, integrated control strategies include chemical treatments with copper-based products and preventive measures but the high virulence and fast spreading of the bacterium are hardly controlled by such measures, and especially copper use is questioned because of the possible appearance of copper resistant bacterial strains. The present project aims at the identification of Psa responses to green tea treatment (Gunpowder variety) at sub-lethal concentration (0.4 mg/ml). Methods: Psa cells were cultured in liquid KB (controls) or in KB supplemented with Gunpowder tea (Gunpowder-trateted) at 0.4 mg/ml EGCG for 24 h at 28°C. The microarray experiments on Gunpowder treated or untreated samples in biological triplicate resulted in 6 samples to be analyzed. Conclusions: This work identified important molecular mechanisms involved in Psa responses upon Gunpowder green tea treatment.