ORIGINAL ARTICLE A novel gibberellin 2-oxidase gene CaGA2ox1 in pepper is specifically induced by incompatible plant pathogens Yeon Lee • Young-Cheol Kim • Soo Yong Kim • In-Jung Lee • Doil Choi • Kyung-Hee Paek • Hye Sun Cho • Suk Yoon Kweon • Jeong Mee Park Received: 3 May 2012 / Accepted: 16 May 2012 / Published online: 10 June 2012 Ó Korean Society for Plant Biotechnology and Springer 2012 Abstract Phytohormone balance is increasingly recog- nized as central to the outcome of plant–pathogen interac- tions. Differential screening for genes induced by a non-host pathogen in pepper plants (Capsicum annuum) identified a putative gibberellin 2-oxidase gene, CaGA2ox1. Analysis of the deduced amino acid sequence of CaGA2ox1 showed 53 and 50 % amino acid identity to Pisum sativum PsGA2ox2 and Arabidopsis AtGA2ox6, respectively. Expression in pepper plants of CaGA2ox1 was preferentially increased in response to non-host pathogen inoculation and during the host resistance response. CaGA2ox1 expression increased following treatment with salicylic acid and ethephon (albeit with different induction patterns), but remained unchanged following treatment with methyl jasmonate and abscisic acid. The gene product of CaGA2ox1 is predicted to catalyze the metabolism of GA 4 , and does so in recombinant E. coli extracts. Further PEG-mediated transient expression studies showed that CaGA2ox1 fused with soluble modified green fluorescent protein localized to the cytosol in chili pepper protoplasts. Interestingly, the transcript level of CaGA2ox1 was not affected by treatments of either pepper with bioac- tive GA 4?7 or paclobutrazol, an inhibitor of GA biosynthe- sis. Taken together, these results provide the first evidence that a GA 2-oxidase, which is important in GA metabolism, may also play a role in plant defense signaling and plant– microbe interactions. Keywords CaGA2ox1  Chili pepper (Capsicum annum)  Gibberellin (GA)  Non-host pathogen Introduction When challenged with pathogen invasion, plants activate various defense responses, including activation of signal transduction pathways leading to expression of defense- related genes [such as pathogenesis-related (PR) genes], activation of the hypersensitive response (HR), and syn- thesis of phytoalexins with antimicrobial activity (Dangl et al. 1996). The major signals involved in plant defense responses are salicylic acid (SA), jasmonic acid (JA), and ethylene (ET; Dong 1998; Reymond and Farmer 1998; Guo and Ecker 2004), which together fine-tune the expression of biotic stress-responsive genes in plants (Hammond- Kosack and Parker 2003). However, the interactions between these signaling networks and the signaling path- ways mediated by other phytohormones, such as gibber- ellin (GA) and auxin, have generally remain unresolved. GA is a tetracyclic diterpenoid phytohormone important in several aspects of plant development, including seed germination, leaf expansion, stem elongation, flowering, Electronic supplementary material The online version of this article (doi:10.1007/s11816-012-0235-2) contains supplementary material, which is available to authorized users. Y. Lee  Y.-C. Kim  S. Y. Kim  H. S. Cho  S. Y. Kweon  J. M. Park (&) Green Bio Research Center, KRIBB, Daejeon 305-333, Republic of Korea e-mail: jmpark@kribb.re.kr I.-J. Lee Division of Plant Bioscience, Kyungpook National University, Daegu 702-701, Republic of Korea D. Choi Department of Plant Science, Seoul National University, Seoul 151-921, Republic of Korea K.-H. Paek School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea 123 Plant Biotechnol Rep (2012) 6:381–390 DOI 10.1007/s11816-012-0235-2