2-Aminobenzoic acid of Bacillus sp. BS107 as an ISR determinant against Pectobacterium carotovorum subsp. carotovotrum SCC1 in tobacco Si Young Yang & Myung Ryeol Park & In Seon Kim & Young Cheol Kim & Jung Wook Yang & Choong-Min Ryu Accepted: 8 September 2010 / Published online: 11 December 2010 # KNPV 2010 Abstract Root drench-treatment of tobacco seedlings with Bacillus sp. BS107 (BS107) suppressed disease development caused by the pathogen Pectobacterium carotovorum subsp. carotovotrum SCC1 (SCC1). A determinant of BS107 involved in induced systemic resistance (ISR) against SCC1 was isolated from cell-free culture. ISR bioassay-guided isolation was involved in determining active fractions during chromatography. Mass spectrometry and NMR analyses of the isolated metabolite identified 2- aminobenzoic acid (2-AB) as a main ISR determinant. 2-AB at 2.3 mM suppressed significantly disease development and exhibited no direct contact inhibition of pathogen. Reverse Transcriptase (RT)-PCR analyses of tobacco leaves revealed up-regulation of the induced resistance marker genes such as PR1a, PR1c, PR2 and PR4 by application of 2-AB on the root. Among aminobenzoic acids tested, 2- and 4-aminobenzoic acids showed ISR activity against soft-rot pathogen, but 3-aminobenzoic acid did not. This is the first report that 2-AB exhibits the ISR against SCC1in tobacco. BS107 can play a role in promoting plant defences by secretion of bacterial determinants including 2-AB for elicitation of ISR. Keywords Aminobenzoic acid . Bacillus sp. BS107 . Induced systemic resistance . Soft-rot disease Introduction It is well known that plant growth-promoting rhizo- bacteria (PGPR) help plants to induce resistance against pathogens by secreting biologically-active compounds. Due to their immobility, plants should develop efficient defence mechanisms against plant pathogens, such as fungi, bacteria, and viruses and plant insects and nematodes, by interacting with beneficial rhizobacteria in the soil environment (Cui et al. 2005). Treatment with PGPR around plant roots enhances plant defence systems, provid- ing an environmentally friendly mean as an alterna- tive to synthetic chemicals. Among induction of plant defence mechanisms, rhizobacteria-elicited induced systemic resistance (ISR) displays impres- sive resistance to a wide range of plant diseases Eur J Plant Pathol (2011) 129:371–378 DOI 10.1007/s10658-010-9687-9 S. Y. Yang : M. R. Park : I. S. Kim (*) Division of Applied Bioscience and Biotechnology, Institute of Agriculture Science and Technology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea email: mindzero@chonnam.ac.kr Y. C. Kim Division of Plant Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea J. W. Yang : C.-M. Ryu (*) Laboratory of Microbial Genomics, Industrial Biotechnology and Bioenergy Research Center, KRIBB, Daejon 305-806, Republic of Korea email: cmryu@kribb.re.kr