Ralstonia Solanacearum에 감염된 토마토에서 ACC Deaminase를 생산하는 Methylobacterium spp.의 스트레스 에틸렌 수준 조절 = Stress Ethylene Reduction by ACC Deaminase Producing Methylobacterium spp. in Tomato (Lycopersicon Esculentum Mill.) Infected by Ralstonia Solanacearum

다국어 초록 (Multilingual Abstract)

Biosynthesis of ethylene is usually enhanced with severity of pathogenic infection. Some ethylene synthesis inhibitors are known to significantly decrease the severity of pathogen infections in plants. Bacteria of genus Methylobacterium have been found to stimulate plant growth and regulate the level of ethylene in crop plants. A selective decrease of ethylene can be achieved by plant growth promoting bacteria, for instance Methylobacterium, containing ACC (1-aminocyclopropane-1- carboxylate) deaminase, which cleaves ACC into -ketobutyrate and ammonia in higher plants which leads to reduced ethylene level. This work aimed to test the induction of defense responses in tomato against bacterial wilt by stress ethylene level reduction mediated by the ACC deaminase activity of Methylobacterium strains. In greenhouse experiments, the disease index value observed in Methylobacterium strains treated tomato and red pepper plants were lower than that of uninoculated treatment. Plants treated with Methylobacterium strains challenge inoculated with Ralstonia solanacearum (RS) showed significantly reduced disease symptom and lowered ethylene emission under greenhouse condition. The ACC and ACO (1-aminocyclopropane-1- carboxylate oxidase) accumulated in the tomato leaves were significantly reduced with Methylobacterium strains inoculation compared to treatment with pathogen alone. Similar to ACC oxidase activity, ACC oxidase related gene expression also increased in tomato treated with Ralstonia solanacearum alone compared to Methylobacterium strains treatment. In addition pathogenesis-related (PR) proteins related to ISR (Induced systemic resistance) including -1,3-glucanase, phenylalanine ammonia-lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) were increased in Methylobacterium strain inoculated tomato plants. A significant increase in -1,3-glucanase and PAL related genes expression was found in all of the Methylobacterium spp. treatments compared to the Ralstonia solanacearum alone treatment. This study supports that the Methylobacterium strains might increase the activity of defense enzymes by modulating the ethylene biosynthesis pathway, suggesting the possibility of using Methylotrophic bacteria as potential bio-control agents.