Project description:Bacillus thuringiensis, a well-known and effective bio-insecticide, has attracted considerable attention as a potential biological control agent for the suppression of plant diseases. Treatment of tomato roots with a filter-sterilized cell-free filtrate (CF) of B. thuringiensis systemically suppresses bacterial wilt caused by Ralstonia solanacearum through systemic activation of the plant defense system. Comparative analysis of the expression of the Pathogenesis-Related 1(P6) [PR-1(P6)] gene, a marker for induced resistance to pathogens, in various tissues of tomato plants treated with CF on their roots suggested that the B. thuringiensis-induced defense system was activated in the leaf, stem, and main root tissues, but not in the lateral root tissue. At the same time, the growth of R. solanacearum was significantly suppressed in the CF-treated main root tissue but not in the CF-treated lateral root tissue. This distinct activation of the defense reaction and suppression of R. solanacearum were reflected by the differences in the transcriptional profiles of the main and lateral tissues in response to the CF. In the CF-treated main root tissue, but not CF-treated lateral root tissue, the expression of several salicylic acid (SA)-responsive defense-related genes was specifically induced, whereas jasmonic acid (JA)-related gene expression was either down-regulated or not induced in response to the CF. On the other hand, genes encoding ethylene (ET)-related proteins were induced equally in both the main and lateral root tissues. Taken together, the co-activation of SA-dependent signaling pathway with ET-dependent signaling pathway and suppression of JA-dependent signaling pathway may play key roles in B. thuringiensis-induced resistance to R. solanacearum in tomato plants. Gene expression was measured in main and lateral root tissues of tomato treated with Bacillus thuringiensis or distilled water-treated control at 48 hours after treatment. Two independent experiments were performed at each tissue (main root or lateral root tissue) for each treatment (Bacillus thuringiensis or distilled water control).
Project description:Bacillus thuringiensis, a well-known and effective bio-insecticide, has attracted considerable attention as a potential biological control agent for the suppression of plant diseases. Treatment of tomato roots with a filter-sterilized cell-free filtrate (CF) of B. thuringiensis systemically suppresses bacterial wilt caused by Ralstonia solanacearum through systemic activation of the plant defense system. Comparative analysis of the expression of the Pathogenesis-Related 1(P6) [PR-1(P6)] gene, a marker for induced resistance to pathogens, in various tissues of tomato plants treated with CF on their roots suggested that the B. thuringiensis-induced defense system was activated in the leaf, stem, and main root tissues, but not in the lateral root tissue. At the same time, the growth of R. solanacearum was significantly suppressed in the CF-treated main root tissue but not in the CF-treated lateral root tissue. This distinct activation of the defense reaction and suppression of R. solanacearum were reflected by the differences in the transcriptional profiles of the main and lateral tissues in response to the CF. In the CF-treated main root tissue, but not CF-treated lateral root tissue, the expression of several salicylic acid (SA)-responsive defense-related genes was specifically induced, whereas jasmonic acid (JA)-related gene expression was either down-regulated or not induced in response to the CF. On the other hand, genes encoding ethylene (ET)-related proteins were induced equally in both the main and lateral root tissues. Taken together, the co-activation of SA-dependent signaling pathway with ET-dependent signaling pathway and suppression of JA-dependent signaling pathway may play key roles in B. thuringiensis-induced resistance to R. solanacearum in tomato plants.
Project description:The soil-borne bacterial pathogen Ralstonia solanacearum invades a broad range of plants through roots, resulting in wilting of the plant, but no effective protection against this disease has been developed. Two R. solanacearum resistance-inducing compounds were biochemically isolated from tobacco and identified as sclareol and cis-abienol, diterpenes. When exogenously applied to their roots, these diterpenes induced resistance to R. solanacearum in tobacco, tomato, and Arabidopsis plants without exhibiting any antimicrobial activity. Structure-activity correlation analysis of sclareol-related compounds revealed that the hydroxyl group at the eighth carbon position is responsible for the activity for inducing resistance. Microarray analysis identified many sclareol-responsive Arabidopsis genes, such as those encoding or with role in ABC transporters, biosynthesis and signaling of defense-related signal molecules, and mitogen-activated protein kinase (MAPK) cascades. Sclareol-induced R. solanacearum resistance was partially compromised in Arabidopsis mutants defective in the ABC transporter AtPDR12, the MAPK MPK3, and ethylene and abscisic acid signaling pathways. Transgenic tobacco plants in which NtPDR1, a tobacco homolog of AtPDR12, was silenced exhibited also reduced resistance. These results suggest that multiple host factors are involved in resistance to R. solanacearum induced by sclareol and its related compounds and that these compounds can be used to protect crops from bacterial wilt disease. Genes that were preferentially expressed in Arabidopsis roots 2 hours after treatment with sclareol were explored. The microarray analysis was performed in triplicate.
Project description:The soil-borne bacterial pathogen Ralstonia solanacearum invades a broad range of plants through roots, resulting in wilting of the plant, but no effective protection against this disease has been developed. Two R. solanacearum resistance-inducing compounds were biochemically isolated from tobacco and identified as sclareol and cis-abienol, diterpenes. When exogenously applied to their roots, these diterpenes induced resistance to R. solanacearum in tobacco, tomato, and Arabidopsis plants without exhibiting any antimicrobial activity. Structure-activity correlation analysis of sclareol-related compounds revealed that the hydroxyl group at the eighth carbon position is responsible for the activity for inducing resistance. Microarray analysis identified many sclareol-responsive Arabidopsis genes, such as those encoding or with role in ABC transporters, biosynthesis and signaling of defense-related signal molecules, and mitogen-activated protein kinase (MAPK) cascades. Sclareol-induced R. solanacearum resistance was partially compromised in Arabidopsis mutants defective in the ABC transporter AtPDR12, the MAPK MPK3, and ethylene and abscisic acid signaling pathways. Transgenic tobacco plants in which NtPDR1, a tobacco homolog of AtPDR12, was silenced exhibited also reduced resistance. These results suggest that multiple host factors are involved in resistance to R. solanacearum induced by sclareol and its related compounds and that these compounds can be used to protect crops from bacterial wilt disease.
Project description:Investigation of whole genome gene expression level changes in the bacterial wilt pathogen Ralstonia solanacearum, strain GMI1000 at 20°C and 28°C in culture and in planta. The tropical strain GMI1000 cannot wilt tomato plants at 20°C although it can cause full-blown disease at 28°C. A 16 array study using total RNA recovered from the following: 8 separate cultures of Ralstonia solanacearum strain GMI1000 grown in rich medium-CPG (4 grown at 20°C and 4 grown at 28°C) 8 separate in planta samples of Ralstonia solanacearum strain GMI1000 harvested from diseased tomato plants cv. BonnyBest (4 recovered from plants grown at 20°C and 4 from plants grown at 28°C) Each array (4-plex format) measures the expression level of 5061 genes from Ralstonia solanacearum strain GMI1000 with 2 to 6, 40-70 mer probes per gene, with two-fold technical redundancy. The arrays also contain probes for intergenic regions with no technical replicates.
Project description:Investigation of whole genome gene expression level changes in the bacterial wilt pathogen Ralstonia solanacearum, strain UW551 at 20°C and 28°C in culture and in planta. The temperatel strain UW551 can wilt and cause full-blown disease on tomato plants at 28°C as well as at 20°C. A 16 array study using total RNA recovered from the following: 8 separate cultures of Ralstonia solanacearum strain UW551 grown in rich medium-CPG (4 grown at 20°C and 4 grown at 28°C) 8 separate in planta samples of Ralstonia solanacearum strain UW551 harvested from diseased tomato plants cv. BonnyBest (4 recovered from plants grown at 20°C and 4 from plants grown at 28°C) Each array (4-plex format) measures the expression level of 4318 genes from Ralstonia solanacearum strain UW551 with 2 to 6, 40-70 mer probes per gene, with two-fold technical redundancy. The arrays also contain probes for intergenic regions with no technical replicates.
Project description:Biofilm lifestyle is critical for bacterial pathogens to colonize and protect themselves from host immunity and antimicrobial chemicals in plants and animals. The formation and regulation mechanism of phytobacterial biofilm are still obscure. Here, we found that Ralstonia solanacearum Resistance to ultraviolet C (RuvC) is highly abundant in biofilm and positively regulates pathogenicity by governing systemic movement in tomato xylem. RuvC protein accumulates at the later stage of biofilm and specifically targets the Holliday junction (HJ) like structures to disrupt biofilm extracellular DNA (eDNA) lattice, thus facilitating biofilm dispersal. Recombinant RuvC protein can resolve extracellular HJ prevent bacterial biofilm formation. Heterologous expression of R. solanacearum or Xanthomonas oryzae pv. oryzae RuvC with plant secretion signal in tomato or rice confers resistance to bacterial wilt or bacterial blight disease, respectively. Plant chloroplast localized HJ resolvase monokaryotic chloroplast 1 (MOC1) which is structural similar to bacterial RuvC shows a strong inhibit effect on bacterial biofilm formation. Re-localization of SlMOC1 to apoplast in tomato roots leads to increase resistance to bacterial wilt. Our novel finding reveals a critical pathogenesis mechanism of R. solanacearum and provides an efficient biotechnology strategy to improve plant resistance to bacteria vascular disease.