The phytotoxin coronatine and methyl jasmonate impact multiple phytohormone pathways in tomato

The phytotoxin coronatine and methyl jasmonate impact multiple phytohormone pathways in tomato

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The phytotoxin coronatine and methyl jasmonate impact multiple phytohormone pathways in tomato Srinivasa Rao Uppalapati 1 , Patricia Ayoubi 2 , Hua Weng 2 , David A. Palmer 1 , Robin E. Mitchell 3 , William Jones 4 and Carol L. Bender 1,* 1 Department of Entomology and Plant Pathology, 2 Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA, 3 Horticulture and Food Research Institute of New Zealand, Private Bag 92 169, Auckland, New Zealand, and 4 Horticulture and Food Research Institute of New Zealand, Private Bag 11 030, Palmerston North, New Zealand Received 8 November 2004; revised 26 December 2004; accepted 7 January 2005. * For correspondence (fax 405 744 9945; e-mail cbender@okstate.edu). Summary Coronatine (COR) is a phytotoxin produced by several pathovars of Pseudomonas syringae and consists of coronafacic acid (CFA), an analog of methyl jasmonic acid (MeJA), and coronamic acid (CMA), which resembles 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor to ethylene. An understanding of how COR functions, is perceived by different plant tissues, and the extent to which it mimics MeJA remain unclear. In this study, COR and related compounds were examined with respect to structure and function. The results indicate that conjugation of CFA to an amino acid is required for optimal activity in tomato, including chlorosis, changes in chloroplast structure, cell wall thickening, accumulation of proteinase inhibitors, induction of anthocyanins, and root growth inhibition. cDNA microarrays were utilized to understand the molecular processes that are regulated by MeJA, COR, CFA and CMA in tomato leaves. A comparison of COR- and MeJA- regulated transcriptomes revealed that COR regulated 35% of the MeJA-induced genes. There was signi±cant overlap in the number of COR and CFA-regulated genes with CFA impacting the expression of 39.4% of the COR-regulated genes. Taken together, the results of biological assays, ultrastructural studies, and gene expression pro±ling demonstrate that: (1) the intact COR molecule impacts signaling in tomato via the jasmonic acid, ethylene, and auxin pathways; (2) CMA does not function as a structural analog of ACC; (3) COR has a broader range of functions than either CFA or CMA; and (4) COR and MeJA share similar, but not identical activities and impact multiple phytohormone pathways in tomato. Keywords: auxin, ethylene, jasmonic acid, octadecanoid, Pseudomonas syringae . Introduction Coronatine (COR) is a non-host-speci±c phytotoxin pro- duced by several members of the Pseudomonas syringae group of pathovars (Bender et al. , 1999; Cintas et al. , 2002; Mitchell, 1982). The toxin acts as a virulence factor in P. syringae pv. tomato , allowing the pathogen to obtain higher population densities and develop larger lesions than COR- defective strains (Bender et al. , 1987; Brooks et al. , 2004; Mittal and Davis, 1995; Pen ˜ aloza-Va ´zquez et al. , 2000). The most prominent symptom observed in leaf tissue treated with COR or infected with COR-producing strains of P. syr- ingae is an intense spreading chlorosis (Gnanamanickam et al.
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This note was uploaded on 08/01/2009 for the course HORT hor-11-12 taught by Professor Park during the Spring '09 term at A.T. Still University.

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The phytotoxin coronatine and methyl jasmonate impact multiple phytohormone pathways in tomato

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