Hai-Ling Jin,3 and
1Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University; Engineering Center of Bioresource Pesticide in Jiangsu Province; Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture; Nanjing 210095, China; 2College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China; 3Department of Plant Pathology and Microbiology, Center for Plant Cell Biology and Institute for Integrative Genome Biology, University of California, Riverside, CA 92521 U.S.A.
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Accepted 27 December 2010.
Bacillus cereus AR156 is a plant growth–promoting rhizobacterium that induces resistance against a broad spectrum of pathogens including Pseudomonas syringae pv. tomato DC3000. This study analyzed AR156-induced systemic resistance (ISR) to DC3000 in Arabidopsis ecotype Col-0 plants. Compared with mock-treated plants, AR156-treated ones showed an increase in biomass and reductions in disease severity and pathogen density in the leaves. The defense-related genes PR1, PR2, PR5, and PDF1.2 were concurrently expressed in the leaves of AR156-treated plants, suggesting simultaneous activation of the salicylic acid (SA)- and the jasmonic acid (JA)- and ethylene (ET)-dependent signaling pathways by AR156. The above gene expression was faster and stronger in plants treated with AR156 and inoculated with DC3000 than that in plants only inoculated with DC3000. Moreover, the cellular defense responses hydrogen peroxide accumulation and callose deposition were induced upon challenge inoculation in the leaves of Col-0 plants primed by AR156. Also, pretreatment with AR156 led to a higher level of induced protection against DC3000 in Col-0 than that in the transgenic NahG, the mutant jar1 or etr1, but the protection was absent in the mutant npr1. Therefore, AR156 triggers ISR in Arabidopsis by simultaneously activating the SA- and JA/ET-signaling pathways in an NPR1-dependent manner that leads to an additive effect on the level of induced protection.
© 2011 The American Phytopathological Society