掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.pmpp.2023.101970

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DOI： 10.1101/2022.12.28.521631

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media {SA}  

<jats:p>Plants protect themselves from microorganisms by inducing pattern-triggered immunity (PTI) <jats:italic>via</jats:italic> 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 <jats:italic>Brachypodium distachyon</jats:italic>. 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 <jats:italic>B. distachyon</jats:italic>. 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.</jats:p>

DOI： 10.3389/fpls.2022.1004184

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1007/s10327-022-01077-2

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その他リンク： https://link.springer.com/article/10.1007/s10327-022-01077-2/fulltext.html

担当区分：筆頭著者,　責任著者   掲載種別：論文集(書籍)内論文  

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担当区分：責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1111/mpp.13198

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/mpp.13198

掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

Rhizoctonia 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.

DOI： 10.3390/life12010076

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Pseudomonas 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.

DOI： 10.1264/jsme2.ME21076

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Korean Society of Plant Pathology  

Ralstonia syzygii subsp. indonesiensis (Rsi, former name: Ralstonia solanacearum phylotype IV) PW1001, a causal agent of potato wilt disease, induces hypersensitive response (HR) on its non-host eggplant (Solanum melongena cv. Senryo-nigou). The disaccharide trehalose is involved in abiotic and biotic stress tolerance in many organisms. We found that trehalose is required for eliciting HR on eggplant by plant pathogen Rsi PW1001. In R. solanacearum, it is known that the OtsA/OtsB pathway is the dominant trehalose synthesis pathway, and otsA and otsB encode trehalose-6-phosphate (T6P) synthase and T6P phosphatase, respectively. We generated otsA and otsB mutant strains and found that these mutant strains reduced the bacterial trehalose concentration and HR induction on eggplant leaves compared to wild-type. Trehalose functions intracellularly in Rsi PW1001 because addition of exogenous trehalose did not affect the HR level and ion leakage. Requirement of trehalose in HR induction is not common in R. solanacearum species complex because mutation of otsA in Ralstonia pseudosolanacearum (former name: Ralstonia solanacearum phylotype I) RS1002 did not affect HR on the leaves of its non-host tobacco and wild eggplant Solanum torvum. Further, we also found that each otsA and otsB mutant had reduced ability to grow in a medium containing NaCl and sucrose, indicating that trehalose also has an important role in osmotic stress tolerance.

DOI： 10.5423/ppj.oa.06.2021.0087

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その他リンク： http://ppjonline.org/journal/view.php?doi=10.5423/PPJ.OA.06.2021.0087

掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.micres.2021.126869

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC MICROBIOLOGY  

<jats:p>
<jats:named-content content-type="genus-species">Pseudomonas amygdali</jats:named-content>
pv.
<jats:italic>tabaci</jats:italic>
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
<jats:named-content content-type="genus-species">P. amygdali</jats:named-content>
pv.
<jats:italic>tabaci</jats:italic>
6605 as a circular chromosome from reads using a PacBio sequencer.
</jats:p>

DOI： 10.1128/MRA.00405-21

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER  

Virulence factor regulator (Vfr) is an indispensable transcription factor in the expression of virulence in the phytopathogenic bacteria Pseudomonas syringae. However, the function of Vfr is not known so far. The deletion of vfr resulted in the loss of surface swarming motility and reduced the virulence in P. syringae pv. tabaci (Pta) 6605. In order to identify the target genes of Vfr, we screened the sequences that bind to Vfr by chromatin immune precipitation (ChIP) and sequencing methods using the closely related bacterium P. syringae pv. syringae (Pss) B728a. For this purpose we first generated a strain that possesses the recombinant gene vfr::FLAG in Pss B728a, and performed ChIP using an anti-FLAG antibody. Immunoprecipitated DNA was purified and sequenced with Illumina HiSeq. The Vfr::FLAG-specific peaks were further subjected to an electrophoresis mobility-shift assay, and the promoter regions of locus tag for Psyr_0578, Psyr_1776, and Psyr_2237 were identified as putative target genes of Vfr. These genes encode plant pathogen-specific methyl-accepting chemotaxis proteins (Mcp). These mcp genes seem to be involved in the Vfr-regulated expression of virulence.

DOI： 10.1016/j.bbrep.2021.100944

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER HEIDELBERG  

Pseudomonas 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.

DOI： 10.1007/s00438-020-01745-y

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

HopH1 is an effector protein ofPseudomonas syringaepv.tomatoDC3000 andP.syringaepv.syringaeB728a and is a homolog of the putative Zn-dependent protease effector Rip36 ofRalstonia solanacearum, which induces hypersensitive response (HR) cell death in a nonhost plant,Solanum torvumSw. cv. Torubamubiga. AlthoughP.syringaepv.phaseolicola(Pph) 1448A neither produces HopH1 nor induces HR cell death,hopH1-introducedPph1448A acquired the ability to induce HR. These results indicate that the putative Zn-protease HopH1 effector induces HR cell death in nonhostS.torvum.

DOI： 10.1007/s10327-020-00961-z

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPANESE SOC MICROBIAL ECOLOGY, DEPT BIORESOURCE SCIENCE  

gamma-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 Delta mcpG mutant abolished chemotaxis to 10 mM GABA. However, Delta mcpG retained chemotaxis to proteinogenic amino acids and succinic semialdehyde, a structural analog of GABA. Furthermore, Delta mcpG 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.

DOI： 10.1264/jsme2.ME20114

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE RESEARCH  

Rhizoctonia 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.

DOI： 10.1038/s41598-020-71968-x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：KOREAN SOC PLANT PATHOLOGY  

Pseudomonas syringae pv. tabaci 6605 has two multidrug resistance (MDR) efflux pump transporters, MexAB-OprM and MexEF-OprN. To understand the role of these MDR efflux pumps in virulence, we generated deletion mutants, Delta mexB, Delta mexF, and Delta mexB Delta mexF, and investigated their sensitivity to plant-derived antimicrobial compounds, antibiotics, and virulence. Growth inhibition assays with KB soft agar plate showed that growth of the wild-type (WT) was inhibited by 5 mu l of 1 M catechol and 1 M coumarin but not by other plant-derived potential antimicrobial compounds tested including phytoalexins. The sensitivity to these compounds tended to increase in Delta mexB and Delta mexB Delta mexF mutants. The Delta mexB Delta mexF mutant was also sensitive to 2 M acetovanillone. The mexAB-oprM was constitutively expressed, and activated in the Delta mexF and Delta mexB Delta mexF mutant strains. The swarming and swimming motilities were impaired in Delta mexF and Delta mexB Delta rnexF mutants. The flood inoculation test indicated that bacterial populations in all mutant strains were significantly lower than that of WT, although all mutants and WT caused similar disease symptoms. These results indicate that MexAB-OprM extrudes plant-derived catechol, acetovanillone, or coumarin, and contributes to bacterial virulence. Furthermore, MexAB-OprM and MexEF-OprN complemented each other's functions to some extent.

DOI： 10.5423/PPJ.OA.11.2019.0273

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Quorum sensing (QS) is a mechanism for bacterial cell-cell communication using QS signals. N-acyl-homoserine lactones (AHLs), QS signals in Pseudomonas syringae pv. tabaci (Pta) 6605, are synthesized by an AHL synthase (PsyI) and recognized by the cognate transcription factor PsyR. To reveal the role of PsyR in virulence, we generated a psyR mutant and complemented strains of Pta 6605 and found that the psyR mutant is remarkably reduced in AHL production and ability to cause disease and propagate in host tobacco leaves. The phenotypes of complemented strains were restored to that of the wild type (WT). Because the psyR mutant lost nearly all AHL production, we investigated the function of PsyR in the transcription of psyI and production of AHL. Electrophoretic mobility shift assays suggested that the recombinant PsyR protein binds the promoter region of psyI but not psyR without AHL. The addition of AHL did not significantly affect this binding. The binding core sequence of this region was identified as a 20-bp lux box-like sequence. To reveal the function of PsyR and AHL on psyI transcription, we constructed a psyI promoter::lacZYA chimeric reporter gene, and inserted it into the WT and psyI mutant of Pta 6605. beta-galactosidase activity increased in a bacterial density-dependent manner in the WT and also in a psyI mutant after the addition of exogenous AHL. These results indicate that the solo PsyR binds the lux box in the psyI promoter and activates transcription in the concomitant presence of AHL.

DOI： 10.1007/s10327-019-00893-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

An ethyl acetate extract of Arabidopsis thaliana plants was tested for the presence of endogenous suppressor(s) (ES), and the active fraction, which partitioned into water phase contained a molecule(s) < 3000 Da based on a rough estimate using sized membrane filters. Foliar application of the ES enabled typically nonpathogenic fungi (non-adapted pathogens) to cause disease symptoms on A. thaliana. Consistently, the ES fraction severely suppressed the oxidative burst and the expression of defense-related genes such as FRK1, NHO1, WRKY22, WRKY29, PEN2, and PEN3 in plants challenged with non-adapted fungus Colletotrichum gloeosporioides or the fungal elicitor chitin.

DOI： 10.1007/s10327-019-00897-z

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Saccharin is generated from probenazole (PBZ) in plants and acts as a plant defense activator. Our study of the mechanism underlying saccharin-induced systemic acquired resistance in Arabidopsis thaliana suggests an antagonistic interaction between salicylic acid (SA)- and jasmonic acid (JA)-signaling as revealed through gene expression analyses. In wild-type plants (Col-0) exposed to saccharin, there was a consistent increase in callose deposition and in expression of SA-marker genes, PR1 and PR2, which coincided with a decrease in expression of JA-marker genes such as VSP2, LOX2 and PDF1.2. Actually, pretreatment of Col-0 with saccharin or PBZ conferred resistance to Pseudomonas syringae pv. tomato DC3000, but not to Pectobacterium carotovorum subsp. carotovorum, Botrytis cinerea, or Colletotrichum higginsianum. Enhanced expression of SA- and JA-marker genes and the augmented deposition of callose were evident after a challenge with virulent DC3000 in saccharin-pretreated plants. Consistently, pretreatment of saccharin and PBZ with SA- and JA-defective mutants led to diminished resistance in NahG-transgenic and npr1 mutant plants, but not in jar1 mutant plants, suggesting that saccharin and PBZ induce resistance in A. thaliana against Pto DC3000 mainly via activation of SA-signaling, leading to suppression of JA/ET-signaling and vice versa. Collectively, an antagonism between SA- and JA-signaling conditioned by saccharin renders resistance to a specific pathogen in Arabidopsis.

DOI： 10.1007/s10327-019-00899-x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Saccharin and its parental compound probenazole (PBZ) are plant activators of effective defense responses to (hemi) biotrophic pathogens. Here, we demonstrate that pretreatment of wheat seedlings with saccharin or PBZ results in a significant reduction of powdery mildew caused by Blumeria graminis f. sp. tritici. Transcriptional analysis revealed the expression of 15 defense-related genes including PR genes, WCI genes, LOX, AOS, NPR1, PAL and WRKY genes in wheat seedlings exposed to either saccharin or PBZ. Moreover, the saccharin- and PBZ-enhanced expression of those genes during fungal infection further proved a close correlation with increased resistance in wheat.

DOI： 10.1007/s10327-019-00900-7

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The evolution of adaptive interactions with beneficial, neutral and detrimental microbes was one of the key features enabling plant terrestrialization. Extensive studies have revealed conserved and unique molecular mechanisms underlying plant-microbe interactions across different plant species; however, most insights gleaned to date have been limited to seed plants. The liverwort Marchantia polymorpha, a descendant of early diverging land plants, is gaining in popularity as an advantageous model system to understand land plant evolution. However, studying evolutionary molecular plant-microbe interactions in this model is hampered by the small number of pathogens known to infect M. polymorpha. Here, we describe four pathogenic fungal strains, Irpex lacteus Marchantia-infectious (MI)1, Phaeophlebiopsis peniophoroides MI2, Bjerkandera adusta MI3 and B. adusta MI4, isolated from diseased M. polymorpha. We demonstrate that salicylic acid (SA) treatment of M. polymorpha promotes infection of the I. lacteus MI1 that is likely to adopt a necrotrophic lifestyle, while this effect is suppressed by co-treatment with the bioactive jasmonate in M. polymorpha, dinor-cis-12-oxo-phytodienoic acid (dn-OPDA), suggesting that antagonistic interactions between SA and oxylipin pathways during plant-fungus interactions are ancient and were established already in liverworts.

DOI： 10.1093/pcp/pcz187

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

DOI： 10.1093/pcp/pcz214

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

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.

DOI： 10.1007/s10327-019-00863-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER GMBH  

Pseudomonas 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 highdensity cells. The activated expressions of rsmX and rsmY were confirmed by Northern blot hybridization, but these expressions were abolished in a.gacA 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.

DOI： 10.1016/j.micres.2019.04.004

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.micres.2018.06.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00438-018-1430-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1042/BSR20171457

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/nph.14849

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10327-017-0756-1

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

The induction of rapid cell death is an effective strategy for plants to restrict biotrophic and hemi-biotrophic pathogens at the infection site. However, activation of cell death comes at a high cost, as dead cells will no longer be available for defense responses nor general metabolic processes. In addition, necrotrophic pathogens that thrive on dead tissue, take advantage of cell death-triggering mechanisms. Mechanisms by which plants solve this conundrum remain described. Here, we identify PLANT SMY2-TYPE ILE-GYF DOMAIN-CONTAINING PROTEIN 1 (PSIG1) and show that PSIG1 helps to restrict cell death induction during pathogen infection. Inactivation of PSIG1 does not result in spontaneous lesions, and enhanced cell death in psig1 mutants is independent of salicylic acid (SA) biosynthesis or reactive oxygen species (ROS) production. Moreover, PSIG1 interacts with SMG7, which plays a role in nonsense-mediated RNA decay (NMD), and the smg7-4 mutant allele mimics the cell death phenotype of the psig1 mutants. Intriguingly, the psig1 mutants display enhanced susceptibility to the hemi-biotrophic bacterial pathogen. These findings point to the existence and importance of the SA- and ROS-independent cell death constraining mechanism as a part of the plant immune system.

DOI： 10.1371/journal.pgen.1007037

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.15252/embj.201694248

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pmpp.2016.02.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pmpp.2016.02.006

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BMC  

Background: Brachypodium distachyon is a promising model plants for grasses. Infections of Brachypodium by various pathogens that severely impair crop production have been reported, and the species accordingly provides an alternative platform for investigating molecular mechanisms of pathogen virulence and plant disease resistance. To date, we have a broad picture of plant immunity only in Arabidopsis and rice; therefore, Brachypodium may constitute a counterpart that displays the commonality and uniqueness of defence systems among plant species. Phytohormones play key roles in plant biotic stress responses, and hormone-responsive genes are used to qualitatively and quantitatively evaluate disease resistance responses during pathogen infection. For these purposes, defence-related phytohormone marker genes expressed at time points suitable for defence-response monitoring are needed. Information about their expression profiles over time as well as their response specificity is also helpful. However, useful marker genes are still rare in Brachypodium.
Results: We selected 34 candidates for Brachypodium marker genes on the basis of protein-sequence similarity to known marker genes used in Arabidopsis and rice. Brachypodium plants were treated with the defence-related phytohormones salicylic acid, jasmonic acid and ethylene, and their transcription levels were measured 24 and 48 h after treatment. Two genes for salicylic acid, 7 for jasmonic acid and 2 for ethylene were significantly induced at either or both time points. We then focused on 11 genes encoding pathogenesis-related (PR) 1 protein and compared their expression patterns with those of Arabidopsis and rice. Phylogenetic analysis suggested that Brachypodium contains several PR1-family genes similar to rice genes. Our expression profiling revealed that regulation patterns of some PR1 genes as well as of markers identified for defence-related phytohormones are closely related to those in rice.
Conclusion: We propose that the Brachypodium immune hormone marker genes identified in this study will be useful to plant pathologists who use Brachypodium as a model pathosystem, because the timing of their transcriptional activation matches that of the disease resistance response. Our results using Brachypodium also suggest that monocots share a characteristic immune system, defined as the common defence system, that is different from that of dicots.

DOI： 10.1186/s12870-016-0749-9

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FRONTIERS MEDIA SA  

Chitin, an N-acetyl-D-glucosamine polymer, is a component of fungal cell walls and a microbe/pathogen-associated molecular pattern that elicits plant defense responses. As polymeric chitin is difficult to handle due to its insolubility in water, many studies on chitin-induced immune responses have used water-soluble low-molecular weight chitin instead. Thus, it is unclear if polymeric chitin can induce resistance. Here, we examined the elicitor activity of chitin nanofiber (CNF) of submicron thickness prepared from polymeric chitin. CNF showed a high dispersing ability in water and induced both reactive oxygen species (ROS) production and chitin-induced defense-related gene expression in Arabidopsis thaliana seedlings. The Arabidopsis chitin elicitor receptor kinase 1 (Atcerk1) mutant, which is impaired in chitin perception, also failed to respond to CNF. CNF exposure triggered ROS generation in suspension-cultured cells from Oryza sativa. Furthermore, pre-treatment of Arabidopsis leaves with CNF effectively reduced pathogen infection by both the fungus Altermaria brassicicola and the bacterium Pseudomonas syringae pv. tomato DC3000. These results demonstrate that CNF has elicitor activity and will help define the role of polymeric chitin in plant immune responses.

DOI： 10.3389/fpls.2015.01098

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.4161/15592324.2014.991569

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Oryza sativa Pto-interacting protein 1a (OsPti1a), an ortholog of tomato (Solanum lycopersicum) SlPti1, functions as a negative regulator of innate immunity in rice (Oryza sativa). In ospti1a mutants, the activation of immune responses, including hypersensitive response-like cell death, is caused by loss of the OsPti1a protein; however, it is as yet unclear how OsPti1a suppresses immune responses. Here, we report that OsPti1a localizes to detergent-resistant membrane fractions of the plasma membrane through lipid modification of the protein's amino terminus, which is highly conserved among Pti1 orthologs in several plant species. Importantly, mislocalization of OsPti1a after deletion of its amino terminus reduced its ability to complement the mutant phenotypes, including hypersensitive response-like cell death. Furthermore, complex formation of OsPti1a depends on its amino terminus-mediated membrane localization. Liquid chromatography-tandem mass spectrometry analysis of OsPti1a complex-interacting proteins identified several defense-related proteins. Collectively, these findings indicate that appropriate complex formation by OsPti1a at the plasma membrane is required for the negative regulation of plant immune responses in rice.

DOI： 10.1104/pp.114.243873

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The AGC kinase OsOxi1, which has been isolated as an interactor with OsPti1a, positively regulates basal disease resistance in rice. In eukaryotes, AGC kinase family proteins are regulated by 3-phosphoinositide-dependent protein kinase 1 (Pdk1). In Arabidopsis, AtPdk1 directly interacts with phosphatidic acid, which functions as a second messenger in both biotic and abiotic stress responses. However, the functions of Pdk1 are poorly understood in plants. We show here that OsPdk1 acts upstream of the OsOxi1-OsPti1a signal cascade in disease resistance in rice. OsPdk1 interacts with OsOxi1 and phosphorylates the Ser283 residue of OsOxi1 in vitro. To investigate whether OsPdk1 is involved in immunity that is triggered by microbial-associated molecular patterns, we analyzed the phosphorylation status of OsPdk1 in response to chitin elicitor. Like OsOxi1, OsPdk1 is rapidly phosphorylated in response to chitin elicitor, suggesting that OsPdk1 participates in signal transduction through pathogen recognition. The overexpression of OsPdk1 enhanced basal resistance against a blast fungus, Magnaporthe oryzae, and a bacterial pathogen, Xanthomonas oryzae pv. oryzae (Xoo). Taken together, these results suggest that OsPdk1 positively regulates basal disease resistance through the OsOxi1-OsPti1a phosphorylation cascade in rice.

DOI： 10.1093/pcp/pcq167

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

OsPti1a, a functional ortholog of tomato SlPti1, negatively regulates both basal resistance and R-gene-mediated resistance in rice. To investigate the molecular function of OsPti1a in defense responses, we searched for components interacting with OsPti1a using a yeast two-hybrid system. One of the interacting proteins is a Ser/Thr kinase that directly phosphorylates OsPti1a in vitro. This protein belongs to the AGC kinase family and is highly similar to AtOxi1, which is induced in response to a wide range of reactive oxygen species (ROS)-generating stimuli in Arabidopsis. Thus, it was designated OsOxi1. OsOxi1 was transiently phosphorylated in response to ROS and chitin elicitor. Both OsOxi1-overexpressing transgenic lines and the ospti1a mutant were highly sensitive to ROS treatment, indicating that OsOxi1 and OsPti1a are involved in ROS-mediated signaling in opposing ways. OsOxi1 is specifically expressed at infection sites where ROS are produced after inoculation with a blast fungus, Magnaporthe oryzae. Overexpression of OsOxi1 enhanced basal resistance to the blast fungus, indicating that OsOxi1 positively regulates disease resistance. OsOxi1 phosphorylates Thr-233 of OsPti1a and a point mutation of Thr-233 enhanced disease susceptibility to a bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo), suggesting that the phosphorylation of OsPti1a by OsOxi1 is essential for basal resistance to Xoo. Taken together, our data suggest that OsOxi1 positively regulates defense responses through the phosphorylation of OsPti1a, causing the release from an OsPti1a-dependent inhibition of the responses.

DOI： 10.1093/pcp/pcq132

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

DOI： 10.14841/jspp.2007.0.499.0

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00438-003-0948-6

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）  

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）  

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記述言語：日本語   出版者・発行元：岡山大学農学部  

An understanding of plant immune systems is important for crop breeding with enhanced disease resistance against pathogen infection. Previous studies reveal that plant has evolved two types of defense mechanisms, which are called &quot;basal resistance&quot; and &quot;R‒gene mediated resistance&quot;, for protecting thewrselves from pathogen attack. Recent studies suggest that both defense systems use a common pathway to activate defense responses, however, the downstream components in both pathways are still obscure. OsPto-interacting protein 1a (OsPti1a), which is a functional ortholog of tomato Pti1, negatively regulates both basal resistance and R‒gene mediated resistance in rice. ospti1a mutant shows lesion formation and accompanying defense responses without pathogen infection. OsPti1a is phosphorylated by upstream kinase oxidative signal inducible1 (OsOxi1) and the phosphorylation of OsPti1a has an important role in activating basal resistance against pathogen infection. Additionally, OsOxi1 is phosphorylated by upstream kinase 3‒phosphoinotiside-dependent protein kinase 1 (OsPdk1). OsPdk1 has an important role for activating basal resistance against compatible pathogen infection. Therefore, OsPdk1-OsOxi1-OsPti1a phosphorylation cascade regulates proper activation of basal resistance in rice. Interestingly, OsPti1a localizes at plasma membrane, and cellular localization of OsPti1a has an important function in suppvessing lesion formation. Especially, N‒terminal amino acid sequences of OsPti1a have a post-translational modification for binding to plasma membrane. Further, OsPti1a forms complexes with potentially plant immune related proteins at plasma membrane, suggesting that plasma membrane localized OsPti1a probably regulates plant immune complex through its phosphorylation during pathogen infection.

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記述言語：日本語   出版者・発行元：植物化学調節学会  

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記述言語：日本語   出版者・発行元：日本植物病理学会  

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記述言語：日本語   出版者・発行元：日本植物病理学会  

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記述言語：日本語   出版者・発行元：日本植物病理学会  

エンドウ褐紋病菌の生産するサプレッサーに応答性のエンドウ遺伝子S64はジャスモン酸合成系の12-oxophytodienoic acid reductase(OPR)と高い相同性を示す.S64の発現制御機構を解析する為,これまでに6つのOPR遺伝子が単離されS64とOPR2が同一であることが明らかとなった.6つのOPR遺伝子の推定アミノ酸配列は互いに80%以上の相同性を有したが,イントロンやプロモーター構造などに多様性が見られた.次に各OPR遺伝子に特異的なプライマーを作成し,RT-PCR法を用いて発現解析を行った.その結果,親和性病原菌の接種,サプレッサー処理で最も強く誘導されるOPR遺伝子はOPR2であることが明らかとなった.また,これまでに解析された各OPR組換えタンパク質の酵素活性と今回の結果から,各OPR遺伝子の相同性による分類は,遺伝子構造,発現の特性,酵素活性による分類と一致し,各々が異なる機能を有することが示唆された.

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記述言語：日本語   出版者・発行元：日本植物病理学会  

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開催年月日： 2023年9月23日 - 2023年9月24日

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記述言語：日本語  

An understanding of plant immune systems is important for crop breeding with enhanced disease resistance against pathogen infection. Previous studies reveal that plant has evolved two types of defense mechanisms, which are called &quot;basal resistance&quot; and &quot;R‒gene mediated resistance&quot;, for protecting thewrselves from pathogen attack. Recent studies suggest that both defense systems use a common pathway to activate defense responses, however, the downstream components in both pathways are still obscure. OsPto-interacting protein 1a (OsPti1a), which is a functional ortholog of tomato Pti1, negatively regulates both basal resistance and R‒gene mediated resistance in rice. ospti1a mutant shows lesion formation and accompanying defense responses without pathogen infection. OsPti1a is phosphorylated by upstream kinase oxidative signal inducible1 (OsOxi1) and the phosphorylation of OsPti1a has an important role in activating basal resistance against pathogen infection. Additionally, OsOxi1 is phosphorylated by upstream kinase 3‒phosphoinotiside-dependent protein kinase 1 (OsPdk1). OsPdk1 has an important role for activating basal resistance against compatible pathogen infection. Therefore, OsPdk1-OsOxi1-OsPti1a phosphorylation cascade regulates proper activation of basal resistance in rice. Interestingly, OsPti1a localizes at plasma membrane, and cellular localization of OsPti1a has an important function in suppvessing lesion formation. Especially, N‒terminal amino acid sequences of OsPti1a have a post-translational modification for binding to plasma membrane. Further, OsPti1a forms complexes with potentially plant immune related proteins at plasma membrane, suggesting that plasma membrane localized OsPti1a probably regulates plant immune complex through its phosphorylation during pathogen infection.

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会議種別：シンポジウム・ワークショップ パネル（指名）  

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記述言語：日本語  

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記述言語：日本語  

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記述言語：日本語  

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プロテオーム解析手法は、遺伝子の機能重複や変異体の致死性に由来する順遺伝学的手法による制約を受けず、翻訳後修飾の解析に非常に有用な手段であることより、未知のシグナル伝達機構を解析するための強力なツールとして期待されている。我々は、「リン酸化」を大規模に解析するショットガン解析技術を確立し、植物免疫を含む広範囲の生命現象の理解に威力を発揮し得ることを報告してきた。<br> 現在、このリン酸化プロテオミクス技術を用い、微生物分子パターン（microbe-associated molecular pattern: MAMP）刺激に伴うリン酸化プロテオームの変動解析を行い、植物免疫を制御する新たな因子の同定に取り組んでいる。また、植物免疫への関与が知られているプロテインキナーゼの基質の同定を目的とした新規手法の確立にも取り組んでいる。本発表では、これらの取り組みについて紹介する。

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これまでの遺伝学的解析から、OsPti1aはイネにおいて真性抵抗性および基礎的抵抗性の発動を負に制御する因子であることを見いだしている。昨年度の年会で、OsPti1aの生理機能にはそのN末端が必須であり、この領域への脂質修飾により細胞膜上に局在していること、ならびに細胞膜上では複合体を形成していることを報告した。そこで、ゲル濾過法によりOsPti1aを含む複合体について詳細に解析したところ、OsPti1aは200～300kDa前後の複合体を形成しているのに対し、N末側を欠損することにより、複合体のサイズが小さく変化することが確認された。すなわち、OsPti1aが機能するためには、そのN末端を介して細胞膜上に局在し、適切な複合体を形成する必要があると考えられた。そこで、OsPti1aを含む膜複合体について明らかにするため、抗-OsPti1a抗体を用いてOsPti1aと相互作用する膜複合体構成因子を精製し、質量分析法によりペプチド配列を決定した。これらの同定された候補因子について、OsPti1aとの相互作用を確認し絞り込みを進めている。

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記述言語：日本語  

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イネの病害抵抗性シグナルを負に制御するOsPti1aの生理機能を明らかにするため、細胞内局在について解析した。OsPti1aは、主に細胞膜上のシグナル伝達に重要な足場として知られるdetergent resistant membrane (DRM) 画分に存在し、さらにリン酸化されていることが明らかとなった。このことから、OsPti1aは細胞膜上でリン酸化による制御を受けて機能している可能性が示唆された。OsPti1aのN末端にHA-strepIIタグを付加した場合、ospti1a変異体の表現型を相補しない。OsPti1aのN末端には脂質修飾を受けうる保存されたアミノ酸配列が存在していることから、この領域がOsPti1aの細胞内での局在に影響を与えている可能性が考えられた。そこで、N末端配列が局在に及ぼす影響ついて解析した結果、N末端を欠損させたOsPti1aは細胞膜ではなくCytosolに存在することが確認された。このことから、OsPti1aの膜局在にはN末側配列が必須であり、膜に存在することが抵抗性シグナルの制御に重要であることが示唆された。さらに、粗ミクロソーム画分に存在するOsPti1aは、250-450kDaの分子量にシグナルが検出された。OsPti1aの予測分子質量は約40kDaであることから、細胞膜上において複合体を形成していることが示唆された。

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記述言語：日本語  

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OsPti1aはOsRAR1の上流で機能し、R遺伝子による耐病性シグナル伝達を負に制御する新規な因子である。ospti1a変異体の培養細胞はH2O2に対する感受性が高く、野生型よりも低濃度のH2O2で細胞死が誘導されたことから、ospti1a変異体の表現型がROSシグナルの制御機構の欠失により生じていることが推察された（高橋ら、本大会）。OsPti1aを介した耐病性シグナル伝達機構を明らかにするために、two-hybrid法によりOsPti1aに結合する因子PIP1(Ospti1a-interacting protein 1) を単離した。PIP1はAGCキナーゼファミリーに属し、シロイヌナズナのOXI1( oxidative signal inducible 1)と高い相同性を示す。OXI1はROSシグナルを正に制御することから、PIP1はイネにおいてROSシグナル伝達に関与する可能性が考えられる。AGCキナーゼファミリーは真核生物に広く保存されており、PDK1 (3-phosphoinotiside dependent protein kinase1)によって活性を制御されていることが知られている。そこで、two-hybrid法を用いてPIP1とPDK1の相互作用を解析するとともに、in vitroにおけるPDK1からPIP1へのリン酸化によるシグナル伝達を明らかにした。PDK1のTos17挿入変異体についても解析を進めており、以上の結果とあわせて、OsPti1aを介した耐病性シグナル伝達について考察する。

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記述言語：日本語  

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記述言語：日本語  

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記述言語：日本語  

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記述言語：日本語  

エンドウ褐紋病菌の生産するサプレッサーに応答性のエンドウ遺伝子S64はジャスモン酸合成系の12-oxophytodienoic acid reductase(OPR)と高い相同性を示す.S64の発現制御機構を解析する為,これまでに6つのOPR遺伝子が単離されS64とOPR2が同一であることが明らかとなった.6つのOPR遺伝子の推定アミノ酸配列は互いに80%以上の相同性を有したが,イントロンやプロモーター構造などに多様性が見られた.次に各OPR遺伝子に特異的なプライマーを作成し,RT-PCR法を用いて発現解析を行った.その結果,親和性病原菌の接種,サプレッサー処理で最も強く誘導されるOPR遺伝子はOPR2であることが明らかとなった.また,これまでに解析された各OPR組換えタンパク質の酵素活性と今回の結果から,各OPR遺伝子の相同性による分類は,遺伝子構造,発現の特性,酵素活性による分類と一致し,各々が異なる機能を有することが示唆された.

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記述言語：日本語  

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