受賞国：日本国

受賞国：日本国

受賞国：日本国

掲載種別：研究論文（学術雑誌）  

DOI： 10.1584/jpestics.d23-038

PubMed

掲載種別：研究論文（学術雑誌）  

The Ralstonia solanacearum species complex is a group of globally important plant pathogens. Bacteria in this very large and genetically diverse group all colonize the xylem elements of angiosperm plants and cause high-impact wilting diseases of many crops. Because they threaten economic and food security, several R. solanacearum species complex subgroups are strictly regulated as quarantine pests. Biologically meaningful and consistent nomenclature is essential for organisms that have major economic and regulatory importance, such as plant-pathogenic Ralstonia. There are currently three species of Ralstonia wilt pathogens: R. pseudosolanacearum (corresponding to two phylogenetic groups that are described in the literature as phylotypes I and III), R. solanacearum (phylotypes IIA, IIB, and IIC), and R. syzygii (phylotype IV, containing three subspecies: subsp. syzygii, subsp. celebensis, and subsp. indonesiensis). A recent paper proposed reclassifying phylotype I as a new species named “ Ralstonia nicotianae.” The purpose of this commentary is to register our objection to the taxon “ Ralstonia nicotianae.”

[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

DOI： 10.1094/phytofr-06-23-0071-le

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.joc.3c01789

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/10715762.2023.2277144

PubMed

担当区分：筆頭著者,　最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1146/annurev-micro-032521-030537

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1128/spectrum.00036-23

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/mpp.13374

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pmpp.2023.101995

掲載種別：研究論文（学術雑誌）  

DOI： 10.1124/molpharm.122.000601

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acschembio.2c00907

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/mpp.13322

PubMed

その他URL： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/mpp.13322

掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.jafc.2c06791

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10265-022-01427-3

PubMed

その他URL： https://link.springer.com/article/10.1007/s10265-022-01427-3/fulltext.html

DOI： 10.1584/jpestics.w22-29

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pestbp.2022.105074

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/mpp.13124

その他URL： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/mpp.13124

掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/10715762.2021.1937620

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acschembio.1c00276

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

First, we revisited the reported NMR data of bradyoxetin, a putative cell density factor of Bradyrhizobium japonicum, and found some inconsistencies in the proposed structure. To elucidate the correct structure, we synthesized model oxetane compounds and confirmed that the NMR data of the synthetic compounds did not match those of the reported bradyoxetin. After reinterpreting the reported NMR data, we concluded that bradyoxetin must be chloramphenicol. Next, some derivatives of 2-hydroxy-4-((methylamino)(phenyl)methyl)cyclopentanone (HMCP), which is a putative quorum-sensing molecule of Ralstonia solanacearum, were synthesized. The NMR spectra of the synthesized compounds were completely different from those of the reported natural products. Based on theoretical studies, including the estimation of 1H and 13C NMR chemical shifts using density functional theory calculations, we confirmed the correctness of the structure of the synthesized compound. These results strongly suggest that the proposed structure of HMCP could be incorrect.

DOI： 10.1021/acs.jnatprod.0c01369

PubMed

掲載種別：研究論文（学術雑誌）  

The soil-borne, plant-pathogenic Ralstonia solanacearum strain OE1-1 produces and secretes methyl 3-hydroxymyristate (3-OH MAME) as a quorum sensing (QS) signal, which contributes to its virulence. A global virulence regulator, PhcA, functioning through the QS system, positively regulates the expression of ralA, which encodes furanone synthase, to produce aryl-furanone secondary metabolites, ralfuranones. A ralfuranone-deficient mutant (ΔralA) is weakly virulent when directly inoculated into tomato xylem vessels. To investigate the functions of ralfuranones, we analysed R. solanacearum transcriptome data generated by RNA sequencing technology. ΔralA expressed phcB, which is associated with 3-OH MAME production, and phcA at levels similar to those in strain OE1-1. In addition, ΔralA exhibited down-regulated expression of more than 90% of the QS positively regulated genes, and up-regulated expression of more than 75% of the QS negatively regulated genes. These results suggest that ralfuranones affect the QS feedback loop. Ralfuranone supplementation restored the ability of ΔralA cells to aggregate. In addition, ralfuranones A and B restored the swimming motility of ΔralA to wild-type levels. However, the application of exogenous ralfuranones did not affect the production of the major exopolysaccharide, EPS I, in ΔralA. Quantitative real-time polymerase chain reaction assays revealed that the deletion of ralA results in the down-regulated expression of vsrAD and vsrBC, which encode a sensor kinase and a response regulator, respectively, in the two-component regulatory systems that influence EPS I production. The application of ralfuranone B restored the expression of these two genes. Overall, our findings indicate that integrated signalling via ralfuranones influences the QS and virulence of R. solanacearum.

DOI： 10.1111/mpp.12537

PubMed

DOI： 10.1038/s41598-020-64687-w

掲載種別：研究論文（学術雑誌）  

A gram-negative plant-pathogenic bacterium Ralstonia solanacearum strain OE1-1 produces and extracellularly secretes methyl 3-hydroxymyristate (3-OH MAME), and senses the chemical as a quorum-sensing (QS) signal, activating QS. During QS a functional global transcriptional regulator PhcA, through the 3-OH MAME-dependent two-component system, induces the production of virulence factors including a major extracellular polysaccharide EPS I and ralfuranone. To elucidate the mechanisms of phcA regulation underlying the QS system, among Tn5-mutants from the strain OE1-1, we identified a mutant of RSc1351 gene (phcK), encoding a putative sensor histidine kinase, that exhibited significantly decreased QS-dependent cell aggregation. We generated a phcK-deletion mutant (ΔphcK) that produced significantly less EPS I and ralfuranone than the wild-type strain OE1-1. Quantitative reverse transcription PCR assays showed that the phcA expression level was significantly down-regulated in the ΔphcK mutant but not in other QS mutants. The transcriptome data generated with RNA sequencing technology revealed that the expression levels of 88.2% of the PhcA-positively regulated genes were down-regulated in the ΔphcK mutant, whereas the expression levels of 85.9% of the PhcA-negatively regulated genes were up-regulated. Additionally, the native phcK-expressing complemented ΔphcK strain and the ΔphcK mutant transformed with phcA controlled by a constitutive promoter recovered their cell aggregation phenotypes. Considered together, the results of this study indicate that phcK is required for full phcA expression, thereby driving the QS circuit of R. solanacearum strain OE1-1. This is the first report of the phcA transcriptional regulation of R. solanacearum.

DOI： 10.1111/mpp.12998

PubMed

掲載種別：研究論文（学術雑誌）  

To characterize the molecular mechanisms underlying life-stage transitions in Phytophthora infestans, we initiated a chemical genetics approach by screening for a stage-specific inhibitor of morphological development from microbial culture extracts prepared mostly from actinomycetes from soil in Japan. Of the more than 700 extracts, one consistently inhibited Ph. infestans cyst germination. Purification and identification of the active compound by ESI–MS, 1H-NMR, and 13C-NMR identified β-rubromycin as the inhibitor of cyst germination (IC50 = 19.8 μg/L); β-rubromycin did not inhibit growth on rye media, sporangium formation, zoospore release, cyst formation, or appressorium formation in Ph. infestans. Further analyses revealed that β-rubromycin inhibited the germination of cysts and oospores in Pythium aphanidermatum. A chemical genetic approach revealed that β-rubromycin stimulated the expression of RIO kinase-like gene (PITG_04584) by 60-fold in Ph. infestans. Genetic analyses revealed that PITG_04584, which lacks close non-oomycete relatives, was involved in zoosporogenesis, cyst germination, and appressorium formation in Ph. infestans. These data imply that further functional analyses of PITG_04584 may contribute to new methods to suppress diseases caused by oomycetes.

DOI： 10.1038/s41598-020-79326-7

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Strains of Ralstonia solanacearum species complex (RSSC) are devastating plant pathogens distributed globally with a wide host range and genetic diversity. Many RSSC strains harbor the polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) hybrid gene rmyA/rmyB for ralstonin production. We report that ralstoamides A (1) and B (2), which are ralstonin-like but shorter lipopeptides, were discovered from the Japanese strains using accumulated RSSC genome data and LC/MS-based metabolite analysis. Their structures, including absolute configurations, were elucidated by spectroscopic analysis and chemical techniques. ramA, a PKS-NRPS gene for ralstoamide production, was identified from the producer strains by genome sequencing and gene-deletion experiments. Based on the analysis of biosynthetic genes of ralstoamides and ralstonins, we suggest the occurrence of NRPS-module reduction of rmyA/rmyB genes in some RSSC strains. This possible molecular evolution changed not only the structures, but also the biological activity of RSSC lipopeptides.

DOI： 10.1021/acschembio.0c00605

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Strains of Ralstonia solanacearum species complex (RSSC) cause “bacterial wilt” on a wide range of plant species and thus lead to marked economic losses in agriculture. Quorum sensing (QS), a bacterial cell-cell communication mechanism, controls the virulence of RSSC strains by regulating the production of extracellular polysaccharide (EPS) and secondary metabolites, biofilm formation, and cellular motility. R. solanacearum strain OE1-1 employs (R)-methyl 3-hydroxymyristate (3-OH MAME) as a QS signal, which is synthesized by the PhcB methyltransferase and sensed by the PhcS/ PhcRQ two-component system. We describe the design, synthesis, and biological evaluation of inhibitors of the phc QS system. Initial screening of a small set of QS signal analogues revealed that methyl 3-hydroxy-8-phenyl-octanoate, named, PQI-1 (phc quorum sensing inhibitor-1), inhibited biofilm formation by strain OE1-1. To improve its inhibitory activity, the derivatives of PQI-1 were synthesized, and their QS inhibition activities were evaluated. PQIs-2-5 evolved from PQI-1 more strongly inhibited not only biofilm formation but also the production of ralfuranone and EPS. Furthermore, RNA-Seq analysis revealed that the PQIs effectively inhibited QS-dependent gene expression and repression in strain OE1-1. On the other hand, the PQIs did not affect the canonical QS systems of the representative reporter bacteria. These antagonists, especially PQI-5, reduced wilting symptoms of the tomato plants infected with strain OE1-1. Taken together, we suggest that targeting the phc QS system has potential for the development of chemicals that protect agricultural crops from bacterial wilt disease.

DOI： 10.1021/acschembio.0c00752

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Cupriavidus taiwanensis LMG19424, a β-rhizobial symbiont of Mimosa pudica, harbors phc and tqs quorum sensing (QS), which are the homologous cell-cell communication systems previously identified from the plant pathogen Ralstonia solanacearum and the human pathogen Vibrio cholerae, respectively. However, there has been no experimental evidence reported that these QS systems function in C. taiwanensis LMG19424. We identified (R)-methyl 3-hydroxymyristate (3-OH MAME) and (S)-3-hydroxypentadecan-4-one (C15-AHK) as phc and tqs QS signals, respectively, and characterized these QS systems. The expression of the signal synthase gene phcB and tqsA in E. coli BL21(DE3) resulted in the high production of 3-OH MAME and C15-AHK, respectively. Their structures were elucidated by comparison of EI-MS data and GC/chiral LC retention times with synthetic standards. The deletion of phcB reduced cell motility and increased biofilm formation, and the double deletion of phcB/tqsA caused the accumulation of the metal chelator coproporphyrin III in its mutant culture. Although the deletion of phcB and tqsA slightly reduced its ability to nodulate on aseptically grown seedlings of M. pudica, there was no significant difference in nodule formation between LMG19424 and its QS mutants when commercial soils were used. Taken together, this is the first example of the simultaneous production of 3-OH MAME/C15-AHK as QS signals in a bacterial species, and the importance of the phc/tqs QS systems in the saprophytic stage of C. taiwanensis LMG19424 is suggested.

DOI： 10.1021/acs.jnatprod.0c00054

PubMed

掲載種別：研究論文（学術雑誌）  

Skeletal muscle atrophy causes decreased physical activity and increased risk of metabolic diseases. We investigated the effects of oleamide (cis-9,10-octadecanamide) treatment on skeletal muscle health. The plasma concentration of endogenous oleamide was approximately 30 nM in the male ddY mice under normal physiological conditions. When the stable isotope-labelled oleamide was orally administered to male ddY mice (50 mg/kg), the plasma concentration of exogenous oleamide reached approximately 170 nM after 1 h. Male ddY mice were housed in small cages (one-sixth of normal size) to enforce sedentary behaviour and orally administered oleamide (50 mg/kg/day) for 4 weeks. Housing in small cages decreased tibialis anterior (TA) muscle mass and the cross-sectional area (CSA) of the myofibres in TA muscle. Dietary oleamide alleviated the decreases in TA muscle and resulted in plasma oleamide concentration of approximately 120 nM in mice housed in small cages. Housing in small cages had no influence on the phosphorylation levels of Akt, mTOR, and p70S6K in TA muscle; nevertheless, oleamide increased the phosphorylation levels of the proteins. Housing in small cages increased the expression of LC3-II and p62, but not LC3-I, in TA muscle, and oleamide reduced LC3-I, LC3-II, and p62 expression levels. In C2C12 myotubes, oleamide increased myotube diameter at ≥ 100 nM. Furthermore, the mTOR inhibitor, Torin 1, suppressed oleamide-induced increases in myotube diameter and protein synthesis. These results indicate that dietary oleamide rescued TA muscle atrophy in mice housed in small cages, possibly by activating the PI3K/Akt/mTOR signalling pathway and restoring autophagy flux.

DOI： 10.1017/S0007114520004304

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Pyoverdines, a group of peptide siderophores produced by Pseudomonas species, function not only in iron acquisition, but also in their virulence in hosts. Thus, chemical inhibition of pyoverdine production may be an effective strategy to control Pseudomonas virulence. In the plant pathogen Pseudomonas cichorii SPC9018 (SPC9018), pyoverdine production is required for virulence on eggplant. We screened microbial culture extracts in a pyoverdine-production inhibition assay of SPC9018 and found Streptomyces sp. RM-32 as a candidate-producer. We isolated two active compounds from RM-32 cultures, and elucidated their structures to be actinomycins X2 and D. Actinomycins X2 and D inhibited pyoverdine production by SPC9018 with IC50 values of 17.6 and 29.6 μM, respectively. Furthermore, pyoverdine production in other Pseudomonas bacteria, such as the mushroom pathogen P. tolaasii, was inhibited by the actinomycins. Therefore, these actinomycins may be useful as chemical tools to examine pyoverdine functions and as seed compounds for anti-Pseudomonas virulence agents.

DOI： 10.1080/09168451.2020.1785839

PubMed

掲載種別：研究論文（学術雑誌）  

The Gram-negative soil-borne bacterium Ralstonia solanacearum first infects roots of host plants and then invades xylem vessels. In xylem vessels, the bacteria grow vigorously and produce exopolysaccharides (EPSs) to cause a wilt symptom on host plants. The EPSs are thus the main virulence factors of R. solanacearum. The strain OE1-1 of R. solanacearum produces methyl 3-hydroxymyristate as a quorum-sensing (QS) signal, and senses this QS signal, activating QS. The QS-activated LysR-type transcriptional regulator PhcA induces the production of virulence-related metabolites including ralfuranone and the major EPS, EPS I. To elucidate the function of EPS I, the transcriptomes of R. solanacearum strains were analysed using RNA sequencing technology. The expression of 97.2% of the positively QS-regulated genes was down-regulated in the epsB-deleted mutant ΔepsB, which lost its EPS I productivity. Furthermore, expression of 98.0% of the negatively QS-regulated genes was up-regulated in ΔepsB. The deficiency to produce EPS I led to a significantly suppressed ralfuranone productivity and significantly enhanced swimming motility, which are suppressed by QS, but did not affect the expression levels of phcA and phcB, which encode a methyltransferase required for methyl 3-hydroxymyristate production. Overall, QS-dependently produced EPS I may be associated with the feedback loop of QS.

DOI： 10.1111/mpp.12870

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Ralstonia solanacearum strains are devastating plant pathogens with global distribution, a wide host range, and genetic diversity, and they are now also referred to as the R. solanacearum species complex (RSSC). RSSC strains employ the quorum sensing (QS) system composed of the phcBSR operon to regulate their virulence on plants. The RSSC strains previously examined produce either (R)-methyl 3-hydroxymyristate (3-OH MAME) or (R)-methyl 3-hydroxypalmitate (3-OH PAME) as their QS signals. Analogously, the phylogenetic analyses of the signal synthase PhcB and the signal receptor PhcS from 15 RSSC strains revealed that these proteins have two clades dependent on their QS signal types. However, the biochemical mechanism underlying this selectivity of QS signal production remains to be elucidated. We demonstrated that the PhcB methyltransferases synthesize QS signals from the cognate fatty acids (R)-3-hydroxymyristic acid or (R)-3-hydroxypalmitic acid. The RSSC strains used here produced both fatty acids, and thus the selectivity of QS signal production depends on the activity of PhcB enzymes. On the other hand, the enantioselective supply of the precursors functioned in the production of enantiopure QS signals. The opposite QS signals weakly induced the production of virulence factors in the RSSC strains. Furthermore, the complementation of the phcB gene encoding the 3-OH PAME-type synthase to the phcB-deletion mutant of the 3-OH MAME-producing strain did not rescue its virulence on tomato plants. Taken together, we propose that the specific production of 3-OH MAME/3-OH PAME ensures full virulence of the RSSC strains.

DOI： 10.1021/acschembio.9b00553

PubMed

共著区分：共著  

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Plant pathogenic bacteria possess sophisticated mechanisms to detect the presence of host plants by sensing host-derived compounds. Ralstonia solanacearum, the causative agent of bacterial wilt on solanaceous plants, employs quorum sensing to control the production of the secondary metabolite ralfuranones/ralstonins, which have been suggested to be involved in virulence. Here, we report that d-galactose and d-glucose, plant sugars, activate the production of ralfuranones/ralstonins in R. solanacearum. As a result, two new derivatives, ralfuranone M (1) and ralstonin C (2), were found in the culture extracts, and their structures were elucidated by spectroscopic and chemical methods. Ralstonin C (2) is a cyclic lipopeptide containing a unique fatty acid, (2S,3S,Z)-3-amino-2-hydroxyicos-13-enoic acid, whereas ralfuranone M (1) has a common aryl-furanone structure with other ralfuranones. d-Galactose and d-glucose activated the expression of the biosynthetic ralfuranone/ralstonin genes and in part became the biosynthetic source of ralfuranones/ralstonins. Ralfuranones and ralstonins were detected from the xylem fluid of the infected tomato plants, and their production-deficient mutants exhibited reduced virulence on tomato and tobacco plants. Taken together, these results suggest that activation of ralfuranone/ralstonin production by host sugars functions in R. solanacearum virulence.

DOI： 10.1021/acschembio.9b00301

PubMed

掲載種別：研究論文（学術雑誌）  

The soil-borne bacterium Ralstonia solanacearum invades the roots and colonizes the intercellular spaces and then the xylem. The expression of lecM, encoding a lectin LecM, is induced by an OmpR family response regulator HrpG in R. solanacearum strain OE1-1. LecM contributes to the attachment of strain OE1-1 to the host cells of intercellular spaces. OE1-1 produces methyl 3-hydroxymyristate (3-OH MAME) through a methyltransferase (PhcB) and extracellularly secretes the chemical as a quorum sensing (QS) signal, which activates QS. The expression of lecM is also induced by the PhcA virulence regulator functioning through QS, and the resulting LecM is implicated in the QS-dependent production of major exopolysaccharide EPS I and the aggregation of OE1-1 cells. To investigate the function of LecM in QS, we analysed the transcriptome of R. solanacearum strains generated by RNA sequencing technology. In the lecM mutant, the expression of positively QS-regulated genes and negatively QS-regulated genes was down-regulated (by >90%) and up-regulated (by ~60%), respectively. However, phcB and phcA in the lecM mutant were expressed at levels similar to those in strain OE1-1. The lecM mutant produced significantly less ralfuranone and exhibited a significantly greater swimming motility, which were positively and negatively regulated by QS, respectively. In addition, the extracellular 3-OH MAME content of the lecM mutant was significantly lower than that of OE1-1. The application of 3-OH MAME more strongly increased EPS I production in the phcB-deleted mutant and strain OE1-1 than in the lecM mutant. Thus, the QS-dependent production of LecM contributes to the QS signalling pathway.

DOI： 10.1111/mpp.12757

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1074/jbc.RA118.006111

PubMed

担当区分：最終著者,　責任著者   掲載種別：研究論文（学術雑誌）  

Microorganisms produce and secrete a variety of secondary metabolites including fatty acids, polyketides, terpenoids, alkaloids, and peptides. Among them, many molecules act as chemical signals that play important roles in inter-/intra-species microbial communication or the interaction with host organisms. In this review, I focus on our recent reports of the microbial signaling molecules involved in bacterium-fungus, bacterium-plant, and fungus-plant interactions. Their potential contribution to pest management is also discussed.

DOI： 10.1584/jpestics.J19-02

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）  

会議種別：口頭発表（招待・特別）