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Hwe-Su Yi,Jung Wook Yang,Hye Kyung Choi,SA-YOUL GHIM,류충민 한국식물생명공학회 2012 Plant biotechnology reports Vol.6 No.4
Like the innate immunity in mammals, plants have developed an induced resistance, referred to as systemic acquired resistance (SAR). Recently, defense priming that is not related to the direct activation of defenses,but instead elicits more rapid induction of resistance mechanisms following trigger application, has been proposed to explain the long-lasting effect of SAR. However,the majority of previous studies have focused on understanding the molecular mechanism underlying priming under in vitro and laboratory conditions. This study examined whether defense priming occurred and was detectable with SAR marker genes by a chemical elicitor,benzothiadiazole (BTH), under field conditions. Pepper seedling application of 0.5 mM BTH was sufficient to prime the CaPR4 gene for 20 days as well as to induce SAR against bacterial spot caused by Xanthomonas axonopodis. Transcriptome analysis revealed to prime defense hormonal signaling and antimicrobial compound production genes. At the end of the season, when bacterial spot and Cucumber mosaic virus disease outbreaks naturally occurred, BTH-treated plants demonstrated less disease symptoms. Our results indicate that the priming of SAR genes plays a critical role in plant protection against pathogens under natural conditions.
Choi, Hye Kyung,Song, Geun Cheol,Yi, Hwe-Su,Ryu, Choong-Min [Plenum Pub. Corp.] 2014 Journal of chemical ecology Vol.40 No.8
<P>Plants are defended from attack by emission of volatile organic compounds (VOCs) that can act directly against pathogens and herbivores or indirectly by recruiting natural enemies of herbivores. However, microbial VOC have been less investigated as potential triggers of plant systemic defense responses against pathogens in the field. Bacillus amyloliquefaciens strain IN937a, a plant growth-promoting rhizobacterium that colonizes plant tissues, stimulates induced systemic resistance (ISR) via its emission of VOCs. We investigated the ISR capacity of VOCs and derivatives collected from strain IN937a against bacterial spot disease caused by Xanthomonas axonopodis pv. vesicatoria in pepper. Of 15 bacterial VOCs and their derivatives, 3-pentanol, which is a C8 amyl alcohol reported to be a component of sex pheromones in insects, was selected for further investigation. Pathogens were infiltrated into pepper leaves 10, 20, 30, and 40 days after treatment and transplantation to the field. Disease severity was assessed 7 days after transplantation. Treatment with 3-pentanol significantly reduced disease severity caused by X. axonopodis and naturally occurring Cucumber mosaic virus in field trials over 2 years. We used quantitative real-time polymerase chain analysis to examine Pathogenesis-Related genes associated with salicylic acid (SA), jasmonic acid (JA), and ethylene defense signaling. The expression of Capsicum annuum Pathogenesis-Related protein 1 (CaPR1), CaPR2, and Ca protease inhibitor2 (CaPIN2) increased in field-grown pepper plants treated with 3-pentanol. Taken together, our results show that 3-pentanol triggers induced resistance by priming SA and JA signaling in pepper under field conditions.</P>
Rhizobium soli sp. nov., isolated from soil
Yoon, Jung-Hoon,Kang, So-Jung,Yi, Hwe-Su,Oh, Tae-Kwang,Ryu, Choong-Min Microbiology Society 2010 International journal of systematic and evolutiona Vol.60 No.6
<P>A Gram-negative, non-motile, pale-yellow, rod-shaped bacterial strain, DS-42<SUP>T</SUP>, was isolated from a soil in Korea and its taxonomic position was investigated by a polyphasic study. Strain DS-42<SUP>T</SUP> grew optimally at 25 °C and pH 7.0-8.0. Strain DS-42<SUP>T</SUP> did not form nodules on three different legumes, and the <I>nodD</I> and <I>nifH</I> genes were also not detected by PCR. Strain DS-42<SUP>T</SUP> contained Q-10 as the predominant ubiquinone. The major cellular fatty acid was C18 : 1<I>ω</I>7<I>c</I>. The DNA G+C content was 60.8 mol%. Phylogenetic analyses based on 16S rRNA, <I>atpD</I> and <I>recA</I> gene sequences showed that strain DS-42<SUP>T</SUP> belonged to the genus <I>Rhizobium</I>. Strain DS-42<SUP>T</SUP> showed 16S rRNA gene sequence similarity of 94.1-97.7 % to the type strains of recognized <I>Rhizobium</I> species. DNA-DNA relatedness between strain DS-42<SUP>T</SUP> and the type strains of <I>Rhizobium huautlense</I>, <I>R. galegae</I>, <I>R. loessense</I> and <I>R. cellulosilyticum</I> was 13-19 %, indicating that strain DS-42<SUP>T</SUP> was distinct from them genetically. Strain DS-42<SUP>T</SUP> can also be differentiated from these four phylogenetically related <I>Rhizobium</I> species by various phenotypic properties. On the basis of phenotypic properties, phylogenetic distinctiveness and genetic data, strain DS-42<SUP>T</SUP> is considered to represent a novel species of the genus <I>Rhizobium</I>, for which the name <I>Rhizobium soli</I> sp. nov. is proposed. The type strain is DS-42<SUP>T</SUP> (=KCTC 12873<SUP>T</SUP> =JCM 14591<SUP>T</SUP>).</P>
Lee, Boyoung,Park, Yong-Soon,Yi, Hwe-Su,Ryu, Choong-Min The Korean Society of Plant Pathology 2013 Plant Pathology Journal Vol.29 No.3
Plants protect themselves from diverse potential pathogens by induction of the immune systems such as systemic acquired resistance (SAR). Most bacterial plant pathogens thrive in the intercellular space (apoplast) of plant tissues and cause symptoms. The apoplastic leaf exudate (LE) is believed to contain nutrients to provide food resource for phytopathogenic bacteria to survive and to bring harmful phytocompounds to protect plants against bacterial pathogens. In this study, we employed the pepper-Xanthomonas axonopodis system to assess whether apoplastic fluid from LE in pepper affects the fitness of X. axonopodis during the induction of SAR. The LE was extracted from pepper leaves 7 days after soil drench-application of a chemical trigger, benzothiadiazole (BTH). Elicitation of plant immunity was confirmed by significant up-regulation of four genes, CaPR1, CaPR4, CaPR9, and CaCHI2, by BTH treatment. Bacterial fitness was evaluated by measuring growth rate during cultivation with LE from BTH- or water-treated leaves. LE from BTH-treatment significantly inhibited bacterial growth when compared to that from the water-treated control. The antibacterial activity of LE from BTH-treated samples was not affected by heating at $100^{\circ}C$ for 30 min. Although the antibacterial molecules were not precisely identified, the data suggest that small (less than 5 kDa), heat-stable compound(s) that are present in BTH-induced LE directly attenuate bacterial growth during the elicitation of plant immunity.
( Yong Soon Park ),( Hae Young Jeong ),( Young Mi Sim ),( Hwe Su Yi ),( Choong Min Ryu ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.4
Pseudomonas syringae pv. syringae (Psy) is a major bacterial pathogen of many economically important plant species. Despite the severity of its impact, the genome sequence of the type strain has not been reported. Here, we present the draft genome sequence of Psy ATCC 19310. Comparative genomic analysis revealed that Psy ATCC 19310 is closely related to Psy B728a. However, only a few type III effectors, which are key virulence factors, are shared by the two strains, indicating the possibility of host-pathogen specificity and genome dynamics, even under the pathovar level.