WileyActa Medica Okayama1464-672226112025Comparative Genomic Analysis Identifies FleQ and GcbB as Virulence-Associated Factors in Pseudomonas syringae pv. tabaci Strainse70168ENMuhammad TaufiqHidayatGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityKeiYoshiokaFaculty of Agriculture, Okayama UniversityTakafumiNishimuraGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityShutaAsaiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversitySachikoMasudaCenter for Sustainable Resource Science, RIKEN-TRIPKenShirasuCenter for Sustainable Resource Science, RIKEN-TRIPNanamiSakataGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityMikihiroYamamotoGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityKazuhiroToyodaGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityYukiIchinoseGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityHidenoriMatsuiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityPseudomonas syringae pv. tabaci (Pta) is an important plant pathogen, which causes wildfire disease in Nicotiana species. However, the genetic basis underlying strain-level differences in virulence remains largely unresolved. To address this, we performed a comparative genomic analysis between a highly virulent strain Pta6605 and a less virulent strain Pta7375. Despite high overall genome similarity, we identified key single-nucleotide polymorphisms, including premature stop-codon mutations in seven open reading frames in Pta7375. Notably, point mutations in two regulatory genes, such as fleQ, which encodes a transcription factor essential for flagellar biogenesis and biofilm formation, and gcbB, which encodes a GGDEF domain-containing diguanylate cyclase responsible for cyclic dimeric guanosine monophosphate (c-di-GMP) synthesis, were implicated in virulence disparity. Functional analyses using deletion and locus replacement mutants in the Pta6605 background revealed that the disruption of fleQ markedly reduced motility, flagellin production, c-di-GMP accumulation, biofilm formation and virulence level mirroring the Pta7375 phenotype. The gcbB replacement mutant showed reduced disease symptom development, although c-di-GMP levels remained comparable to the Pta6605 wild type. Locus replacement between strains confirmed that a point mutation in fleQ was the primary driver of reduced motility and flagellin expression in Pta7375. These findings indicate that the reduced virulence of Pta7375 is associated with impaired regulation of flagella-related genes and disruption of the FleQ-mediated c-di-GMP signalling, underscoring the value of comparative genomics in disentangling the complex regulatory networks that govern virulence in plant pathogens.No potential conflict of interest relevant to this article was reported.WileyActa Medica Okayama1464-67222652025Pseudomonas syringae pv. tabaci 6605 Requires Seven Type III Effectors to Infect Nicotiana benthamianae70091ENKanaKuroeGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityTakafumiNishimuraGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversitySachiKashiharaGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityNanamiSakataGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityMikihiroYamamotoGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityKazuhiroToyodaGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityYukiIchinoseGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityHidenoriMatsuiGraduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityType III effectors (T3Es), virulence factors injected into plant cells via the type III secretion system (T3SS), play essential roles in the infection of host plants. Pseudomonas syringae pv. tabaci 6605 (Pta 6605) is the causal agent of wildfire disease in tobacco and harbours at least 22 T3Es in its genome. However, the specific T3Es required by Pta 6605 to infect Nicotiana benthamiana remain unidentified. In this study, we investigated the T3Es that contribute to Pta 6605 infection of N. benthamiana. We constructed Pta 6605 poly-T3E-deficient mutants (Pta DxE) and inoculated them into N. benthamiana. Flood assay, which mimics natural opening-based entry, showed that mutant strains lacking 14-22 T3Es, namely, Pta D14E-D22E mutants, exhibited reduced disease symptoms. By contrast, infiltration inoculation, which involves direct injection into leaves, showed that the Pta D14E to Pta D20E mutants developed disease symptoms. Notably, the Pta D20E, containing AvrE1 and HopM1, induced weak but observable symptoms upon infiltration inoculation. Conversely, no symptoms were observed in either the flood assay or infiltration inoculation for Pta D21E and Pta D22E. Taken together, these findings indicate that the many T3Es such as AvrPto4/AvrPtoB, HopW1/HopAE1, and HopM1/AvrE1 in Pta 6605 collectively contribute to invasion through natural openings and symptom development in N. benthamiana. This study provides the basis for understanding virulence in the host by identifying the minimum T3E repertoire required by Pta 6605 to infect N. benthamiana.No potential conflict of interest relevant to this article was reported.Springer Science and Business Media LLCActa Medica Okayama1345-26308942023Positive chemotaxis to plant apoplastic fluids of Pseudomonas syringae pv. tabaci 6605 and metabolome analysis219223ENYutaWatanabeThe Graduate School of Environmental and Life Science, Okayama UniversityStephany AngeliaTumewuThe Graduate School of Environmental and Life Science, Okayama UniversityHajimeYamadaFaculty of Agriculture, Okayama UniversityHidenoriMatsuiThe Graduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoThe Graduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiThe Graduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaThe Graduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseThe Graduate School of Environmental and Life Science, Okayama UniversityPseudomonas syringae pv. tabaci 6605 (Pta6605) is a causal agent of wildfire disease in host tobacco plants. Although chemotaxis has been shown to be necessary for Pta6605 in tobacco infection, the chemoattractants at the site of infection are unclear. Pta6605 was attracted to the apoplastic fluid from not only host tobacco leaves but also non-host plant leaves, indicating that Pta6605 is attracted to common plant metabolites. Metabolome analysis of apoplastic fluid from tobacco leaves revealed that amino acids including γ-aminobutyric acid and organic acids are abundant, suggesting that these compounds are potential chemoattractants.No potential conflict of interest relevant to this article was reported.Japanese Society of Microbial EcologyActa Medica Okayama1342-63113712022Identification of Aerotaxis Receptor Proteins Involved in Host Plant Infection by Pseudomonas syringae pv. tabaci 6605ME21076ENStephany AngeliaTumewuGraduate School of Environmental and Life Science, Okayama UniversityYutaWatanabeFaculty of Agriculture, Okayama UniversityHidenoriMatsuiFaculty of Agriculture, Okayama UniversityMikihiroYamamotoFaculty of Agriculture, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityPseudomonas syringae pv. tabaci 6605 (Pta6605) is a foliar plant pathogen that causes wildfire disease on tobacco plants. It requires chemotaxis to enter plants and establish infection. While chemotactic signals appear to be the main mechanism by which Pta6605 performs directional movement, the involvement of aerotaxis or energy taxis by this foliar pathogen is currently unknown. Based on domain structures and similarity with more than 50 previously identified putative methyl-accepting chemotaxis proteins (MCPs), the genome of Pta6605 encodes three potential aerotaxis transducers. We identified AerA as the main aerotaxis transducer and found that it possesses a taxis-to-serine-and-repellent (Tsr)-like domain structure that supports a periplasmic 4HB-type ligand-binding domain (LBD). The secondary aerotaxis transducer, AerB, possesses a cytosolic PAS-type LBD, similar to the Aer of Escherichia coli and Pseudomonas aeruginosa. Aerotaxis ability by single and double mutant strains of aerA and aerB was weaker than that by wild-type Pta6605. On the other hand, another cytosolic PAS-type LBD containing MCP did not make a major contribution to Pta6605 aerotaxis in our assay system. Furthermore, mutations in aerotaxis transducer genes did not affect surface motility or chemotactic attraction to yeast extract. Single and double mutant strains of aerA and aerB showed less colonization in the early stage of host plant infection and lower biofilm production than wild-type Pta6605. These results demonstrate the presence of aerotaxis transducers and their contribution to host plant infection by Pta6605.No potential conflict of interest relevant to this article was reported.Frontiers Media S.A.Acta Medica Okayama1664-462X132022Time-series transcriptome of Brachypodium distachyon during bacterial flagellin-induced pattern-triggered immunity1004184ENTsubasaOgasaharaGraduate School of Environmental and Life Science, Okayama UniversityYusukeKouzaiGraduate School of Environmental and Life Science, Okayama UniversityMegumiWatanabeGraduate School of Environmental and Life Science, Okayama UniversityAkihiroTakahashiGraduate School of Environmental and Life Science, Okayama UniversityKotaroTakahagiKihara Institute for Biological Research, Yokohama City UniversityJune-SikKimBioproductivity Informatics Research Team, RIKEN Center for Sustainable Resource ScienceHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityKeiichiMochidaBioproductivity Informatics Research Team, RIKEN Center for Sustainable Resource ScienceYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityPlants protect themselves from microorganisms by inducing pattern-triggered immunity (PTI) via recognizing microbe-associated molecular patterns (MAMPs), conserved across many microbes. Although the MAMP perception mechanism and initial events during PTI have been well-characterized, knowledge of the transcriptomic changes in plants, especially monocots, is limited during the intermediate and terminal stages of PTI. Here, we report a time-series high-resolution RNA-sequencing (RNA-seq) analysis during PTI in the leaf disks of Brachypodium distachyon. We identified 6,039 differentially expressed genes (DEGs) in leaves sampled at 0, 0.5, 1, 3, 6, and 12 hours after treatment (hat) with the bacterial flagellin peptide flg22. The k-means clustering method classified these DEGs into 10 clusters (6 upregulated and 4 downregulated). Based on the results, we selected 10 PTI marker genes in B. distachyon. Gene ontology (GO) analysis suggested a tradeoff between defense responses and photosynthesis during PTI. The data indicated the recovery of photosynthesis started at least at 12 hat. Over-representation analysis of transcription factor genes and cis-regulatory elements in DEG promoters implied the contribution of 12 WRKY transcription factors in plant defense at the early stage of PTI induction.No potential conflict of interest relevant to this article was reported.WileyActa Medica Okayama1464-67222362022HopAZ1, a type III effector of Pseudomonas amygdali pv. tabaci, induces a hypersensitive response in tobacco wildfire-resistant Nicotiana tabacum 'N509'885894ENSachiKashiharaGraduate School of Environmental and Life Science, Okayama UniversityTakafumiNishimuraGraduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityPseudomonas amygdali pv. tabaci (formerly Pseudomonas syringae pv. tabaci; Pta) is a gram-negative bacterium that causes bacterial wildfire disease in Nicotiana tabacum. The pathogen establishes infections by using a type III secretion system to inject type III effector proteins (T3Es) into cells, thereby interfering with the host & apos;s immune system. To counteract the effectors, plants have evolved disease-resistance genes and mechanisms to induce strong resistance on effector recognition. By screening a series of Pta T3E-deficient mutants, we have identified HopAZ1 as the T3E that induces disease resistance in N. tabacum 'N509'. Inoculation with the Pta increment hopAZ1 mutant did not induce resistance to Pta in N509. We also found that the Pta increment hopAZ1 mutant did not induce a hypersensitive response and promoted severe disease symptoms in N509. Furthermore, a C-terminal truncated HopAZ1 abolished HopAZ1-dependent cell death in N509. These results indicate that HopAZ1 is the avirulence factor that induces resistance to Pta by N509.No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama2075-17291212022Surveillance of Pathogenicity of Rhizoctonia solani Japanese Isolates with Varied Anastomosis Groups and Subgroups on Arabidopsis thaliana76ENMai Mohsen AhmedAbdelghanyGraduate School of Environmental and Life Science, Okayama UniversityMariaKurikawaDepartment of Agriculture, Okayama UniversityMegumiWatanabeGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYusukeKouzaiGraduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityRhizoctonia solani is a necrotrophic plant pathogen with a wide host range. R. solani is a species complex consisting of thirteen anastomosis groups (AGs) defined by compatibility of hyphal fusion reaction and subgroups based on cultural morphology. The relationship between such classifications and host specificity remains elusive. Here, we investigated the pathogenicity of seventeen R. solani isolates (AG-1 to 7) in Japan towards Arabidopsis thaliana using leaf and soil inoculations. The tested AGs, except AG-3 and AG-6, induced symptoms in both methods with variations in pathogenicity. The virulence levels differed even within the same AG and subgroup. Some isolates showed tissue-specific infection behavior. Thus, the AGs and their subgroups are suggested to be not enough to define the virulence (host and tissue specificity) of R. solani. We also evaluated the virulence of the isolates on Arabidopsis plants pretreated with salicylic acid, jasmonic acid, and ethylene. No obvious effects were detected on the symptom formation by the virulence isolates, but ethylene and salicylic acid slightly enhanced the susceptibility to the weak and nonvirulent isolates. R. solani seems to be able to overcome the induced defense by these phytohormones in the infection to Arabidopsis.No potential conflict of interest relevant to this article was reported.American Society for MicrobiologyActa Medica Okayama2576-098X10282021Complete Genome Sequence of Pseudomonas amygdali pv. tabaci Strain 6605, a Causal Agent of Tobacco Wildfire Diseasee00405-21ENHidenoriMatsuiGraduate School of Environmental and Life Sciences, Okayama UniversityTakafumiNishimuraGraduate School of Environmental and Life Sciences, Okayama UniversityShutaAsaiCenter for Sustainable Resource Science, RIKENSachikoMasudaCenter for Sustainable Resource Science, RIKENKenShirasuCenter for Sustainable Resource Science, RIKENMikihiroYamamotoGraduate School of Environmental and Life Sciences, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Sciences, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Sciences, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Sciences, Okayama UniversityPseudomonas amygdali pv. tabaci strain 6605 is the bacterial pathogen causing tobacco wildfire disease that has been used as a model for elucidating virulence mechanisms. Here, we present the complete genome sequence of P. amygdali pv. tabaci 6605 as a circular chromosome from reads using a PacBio sequencer.No potential conflict of interest relevant to this article was reported.SpringerActa Medica Okayama1617-46152962021Cluster II che genes of Pseudomonas syringae pv. tabaci 6605, orthologs of cluster I in Pseudomonas aeruginosa, are required for chemotaxis and virulence299312ENStephany AngeliaTumewuGraduate School of Environmental and Life Science, Okayama UniversityYujiroOgawaFaculty of Agriculture, Okayama UniversityTakumiOkamotoFaculty of Agriculture, Okayama UniversityYukaSugiharaFaculty of Agriculture, Okayama UniversityHajimeYamadaFaculty of Agriculture, Okayama UniversityFumikoTaguchiGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityPseudomonas syringae pv. tabaci 6605 (Pta6605) is a causal agent of wildfire disease in host tobacco plants and is highly motile. Pta6605 has multiple clusters of chemotaxis genes including cheA, a gene encoding a histidine kinase, cheY, a gene encoding a response regulator, mcp, a gene for a methyl-accepting chemotaxis protein, as well as flagellar and pili biogenesis genes. However, only two major chemotaxis gene clusters, cluster I and cluster II, possess cheA and cheY. Deletion mutants of cheA or cheY were constructed to evaluate their possible role in Pta6605 chemotaxis and virulence. Motility tests and a chemotaxis assay to known attractant demonstrated that cheA2 and cheY2 mutants were unable to swarm and to perform chemotaxis, whereas cheA1 and cheY1 mutants retained chemotaxis ability almost equal to that of the wild-type (WT) strain. Although WT and cheY1 mutants of Pta6605 caused severe disease symptoms on host tobacco leaves, the cheA2 and cheY2 mutants did not, and symptom development with cheA1 depended on the inoculation method. These results indicate that chemotaxis genes located in cluster II are required for optimal chemotaxis and host plant infection by Pta6605 and that cluster I may partially contribute to these phenotypes.No potential conflict of interest relevant to this article was reported.Japanese Society of Microbial EcologyActa Medica Okayama1342-63113542020Requirement of γ-Aminobutyric Acid Chemotaxis for Virulence of Pseudomonas syringae pv. tabaci 6605ME20114ENStephany AngeliaTumewuGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama Universityγ-Aminobutyric acid (GABA) is a widely distributed non-proteinogenic amino acid that accumulates in plants under biotic and abiotic stress conditions. Recent studies suggested that GABA also functions as an intracellular signaling molecule in plants and in signals mediating interactions between plants and phytopathogenic bacteria. However, the molecular mechanisms underlying GABA responses to bacterial pathogens remain unknown. In the present study, a GABA receptor, named McpG, was conserved in the highly motile plant-pathogenic bacteria Pseudomonas syringae pv. tabaci 6605 (Pta6605). We generated a deletion mutant of McpG to further investigate its involvement in GABA chemotaxis using quantitative capillary and qualitative plate assays. The wild-type strain of Pta6605 was attracted to GABA, while the ΔmcpG mutant abolished chemotaxis to 10 mM GABA. However, ΔmcpG retained chemotaxis to proteinogenic amino acids and succinic semialdehyde, a structural analog of GABA. Furthermore, ΔmcpG was unable to effectively induce disease on host tobacco plants in three plant inoculation assays: flood, dip, and infiltration inoculations. These results revealed that the GABA sensing of Pta6605 is important for the interaction of Pta6605 with its host tobacco plant.No potential conflict of interest relevant to this article was reported.SpringerActa Medica Okayama1345-2630872020HopH1 effectors of Pseudomonas syringae pv. tomato DC3000 and pv. syringae B728a induce HR cell death in nonhost eggplant Solanum torvum2429ENKamrunNaharGraduate School of Natural Science and Technology, Okayama UniversityTakafumiMukaiharaResearch Institute for Biological Sciences, Okayama (RIBS)FumikoTaguchiGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Natural Science and Technology, Okayama UniversityKazuhiroToyodaGraduate School of Natural Science and Technology, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityTomonoriShiraishiResearch Institute for Biological Sciences, Okayama (RIBS)YukiIchinoseGraduate School of Natural Science and Technology, Okayama UniversityHopH1 is an effector protein of Pseudomonas syringae pv. tomato DC3000 and P. syringae pv. syringae B728a and is a homolog of the putative Zn-dependent protease effector Rip36 of Ralstonia solanacearum, which induces hypersensitive response (HR) cell death in a nonhost plant, Solanum torvum Sw. cv. Torubamubiga. Although P. syringae pv. phaseolicola (Pph) 1448A neither produces HopH1 nor induces HR cell death, hopH1-introduced Pph 1448A acquired the ability to induce HR. These results indicate that the putative Zn-protease HopH1 effector induces HR cell death in nonhost S. torvum.No potential conflict of interest relevant to this article was reported.Nature ResearchActa Medica Okayama2045-23221012020Identification of effector candidate genes of Rhizoctonia solani AG-1 IA expressed during infection in Brachypodium distachyon14889ENSobhy S. H.AbdelsalamGraduate School of Environmental and Life Science, Okayama UniversityYusukeKouzaiBioproductivity Informatics Research Team, RIKEN Center for Sustainable Resource ScienceMegumiWatanabeGraduate School of Environmental and Life Science, Okayama UniversityKomakiInoueBioproductivity Informatics Research Team, RIKEN Center for Sustainable Resource ScienceHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversitySeijiTsugeGraduate School of Agriculture, Kyoto Prefectural UniversityKeiichiMochidaInstitute for Plant Science and Resources (IPSR), Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityRhizoctonia solani is a necrotrophic phytopathogen belonging to basidiomycetes. It causes rice sheath blight which inflicts serious damage in rice production. The infection strategy of this pathogen remains unclear. We previously demonstrated that salicylic acid-induced immunity could block R. solani AG-1 IA infection in both rice and Brachypodium distachyon. R. solani may undergo biotrophic process using effector proteins to suppress host immunity before necrotrophic stage. To identify pathogen genes expressed at the early infection process, here we developed an inoculation method using B. distachyon which enables to sample an increased amount of semi-synchronous infection hyphae. Sixty-one R. solani secretory effector-like protein genes (RsSEPGs) were identified using in silico approach with the publicly available gene annotation of R. solani AG-1 IA genome and our RNA-sequencing results obtained from hyphae grown on agar medium. Expression of RsSEPGs was analyzed at 6, 10, 16, 24, and 32 h after inoculation by a quantitative reverse transcription-polymerase chain reaction and 52 genes could be detected at least on a single time point tested. Their expressions showed phase-specific patterns which were classified into 6 clusters. The 23 RsSEPGs in the cluster 1-3 and 29 RsSEPGs in the cluster 4-6 are expected to be involved in biotrophic and necrotrophic interactions, respectively.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama09445013223-2252019Quorum-dependent expression of rsmX and rsmY, small non-coding RNAs, in Pseudomonas syringae7278ENYukikoNakatsuGraduate School of Environmental and Life Science, Okayama UniversityHidenoriMatsuiGraduate School of Environmental and Life Science, Okayama UniversityMikihiroYamamotoGraduate School of Environmental and Life Science, Okayama UniversityYoshiteruNoutoshiGraduate School of Environmental and Life Science, Okayama UniversityKazuhiroToyodaGraduate School of Environmental and Life Science, Okayama UniversityYukiIchinoseGraduate School of Environmental and Life Science, Okayama UniversityPseudomonas syringae pathovars are known to produce N-acyl-homoserine lactones (AHL) as quorum-sensing molecules. However, many isolates, including P. syringae pv. tomato DC3000 (PtoDC3000), do not produce them. In P. syringae, psyI, which encodes an AHL synthase, and psyR, which encodes the transcription factor PsyR required for activation of psyI, are convergently transcribed. In P. amygdali pv. tabaci 6605 (Pta6605), there is one nucleotide between the stop codons of both psyI and psyR. However, the canonical stop codon for psyI in PtoDC3000 was converted to the cysteine codon by one nucleotide deletion, and 23 additional amino acids extended it to a C-terminal end. This resulted in overlapping of the open reading frame (ORF) for psyI and psyR. On the other hand, stop codons in the psyR ORF of P. syringae 7 isolates, including pv. phaseolicola and pv. glycinea, were found. These results indicate that many pathovars of P. syringae have genetically lost AHL production ability by the mutation of their responsible genes. To examine whether PtoDC3000 modulates the gene expression profile in a population-dependent manner, we carried out microarray analysis using RNAs prepared from low- and high-density cells. We found the expressions of rsmX and rsmY remarkably activated in high-density cells. The activated expressions of rsmX and rsmY were confirmed by Northern blot hybridization, but these expressions were abolished in a ΔgacA mutant of Pta6605. These results indicate that regardless of the ability to produce AHL, P. syringae regulates expression of the small noncoding RNAs rsmX/Y by currently unknown quorum-sensing molecules.No potential conflict of interest relevant to this article was reported.SpringerActa Medica Okayama1345-26308562019A class III peroxidase PRX34 is a component of disease resistance in Arabidopsis405412ENLeiZhaoLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityLe Thi PhuongLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityMai Thanh LuanLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityAprilia Nur FitriantiLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityHidenoriMatsuiLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityHirofumiNakagamiRIKEN Center for Sustainable Resource ScienceYoshiteruNoutoshiLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityMikihiroYamamotoLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityYukiIchinoseLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityTomonoriShiraishiLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama UniversityKazuhiroToyodaLaboratory of Plant Pathology and Genetic Engineering, Graduate School of Environmental and Life ScienceOkayama University PRX34 mediates the oxidative burst in Arabidopsis. Here we characterized two additional Arabidopsis prx34 null mutants (prx34-2, prx34-3), besides the well-studied prx34-1. Due to a decrease in corresponding peroxidase, the activity that generates reactive oxygen species (ROS) was significantly lower in cell wall extracts of prx34-2 and prx34-3 plants. Consistently, the prx34-2 and prx34-3 exhibited reduced accumulation both of ROS and callose in Flg22-elicitor-treated leaves, leading to enhanced susceptibility to bacterial and fungal pathogens. In contrast, ectopic expression of PRX34 in the wild type caused enhanced resistance. PRX34 is thus a component for disease resistance in Arabidopsis.No potential conflict of interest relevant to this article was reported.岡山大学農学部Acta Medica Okayama0474-02548611997イチゴ黒斑病菌の生成する宿主特異的毒素103108ENMikihiroYamamotoOccurrence of Alternaria black spot of strawberry was first reported on var.Morioka-16,Among varieties tested,var.Morioka-16 was found to be only one susceptible variety.The pathogen,however,showed pathogenicity on pear leaves which is susceptible to black spot of Japanese pear.The casual pathogen of black spot of strawberry,Alternaria alternata strawberry pathotype produced three host-specific toxins(HSts),which were chemically characterized,and named AF-toxin Ⅰ,Ⅱand Ⅲ,respectively.HSTs are considered as a primary determinant of pathogenicity,that is,interaction between the host plant and the pathogen.We here introduce briefly researchd on host-specific toxin focusing on AF-toxins.No potential conflict of interest relevant to this article was reported.岡山大学農学部Acta Medica Okayama0474-02549012001Structural Characterization of ACC Synthase Genes from Melon and Cucumber and their Promoter Activities Determined by GUS Transient Assay2735ENShinjiroShiomiOguraEmiMikihiroYamamotoReinosukeNakamuraYasutakaKuboAkitsuguInabaIn orader to clarify the differences in regulatory mechanism(s) of the expression of 1-aminocyclopropane-1-carboxylate(ACC) synthase(ACS)genes during ripening in climacteric melon fruit and non-climacteric cucumber fruit, two sets of their genomic DNA sequences, including ca. 2kb of the promoter regions were determined, using PCR-based methods. ACS genes from melon (CMe-ACS1,2) were structurally similar to their counterpart from cucumber (CS-ACS1,2) in terms of size and position of exons and introns, restriction map, and sequencd identity of exeons, introns, proximal 5'-flanking promoter regions and splice junction. Southern blot analysis indicated that each ACS gene is present as a single copy. Transient promoter activity was investigated with two constructs of promoter-β-glucuronidase (GUS) fusion, CMe-ACS1:GUS and CS-ACS1:GUS, in mature mesocarp tissue of the two fruits. In melon disks, GUS activities conferred by the promoters of both CS-ACS1 (-2098～+42) and CMe-ACS-1(-2187～+67) were detected, which were decreased by treatment with 1-methylcyclopropene(1-MCP), an ethylene action inhibitor. In cucumber disks, however, only CS-ACS1:GUS was expressed; the activity was decreased with 1-MCP, and it was not affected by propylene. These results suggest that the promoter of CS-ACS1 has a potential to be expressed in the mesocarp tissue of ripening melon fruit, and that the difference in ethylene biosynthesis between melon and cucumber during ripening may be due to the difference in capability of forming trans-acting factor(s), not due to their ACS1 promoter activities.No potential conflict of interest relevant to this article was reported.