title: Susceptible to intolerance--a range of hormonal actions in a susceptible Arabidopsis pathogen response.
abstract: Ethylene and salicylic acid (SA) are key intermediates in a host's response to pathogens. Previously, we have shown using a tomato compatible interaction that ethylene and SA act sequentially and are essential for disease symptom production. Here, we have examined the relationship between the two signals in the Arabidopsis-Xanthomonas campestris pv. campestris (Xcc) compatible interaction. Preventing SA accumulation by expression of the nahG gene reduced subsequent ethylene production and altered the development of disease symptoms, with plants showing no visible chlorosis. The ethylene insensitive lines, etr1-1 and etr2-1, on the other hand, accumulated SA and exhibited normal but precocious symptom development. Therefore, Arabidopsis, like tomato, was found to exhibit co-operative ethylene and SA action for the production of disease symptoms. However, in Arabidopsis, SA was found to act upstream of ethylene. Jasmonic acid and indole-3-acetic acid levels were also found to increase in response to Xcc. In contrast to ethylene, accumulation of these hormones was not found to be dependent on SA action. These results indicate that the plants response to a virulent pathogen is a composite of multiple signaling pathways.
authors.affiliation: Department of Horticultural Sciences, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: O'Donnell
authors.forename: Eric A
authors.initials: EA
authors.lastname: Schmelz
authors.forename: Patricia
authors.initials: P
authors.lastname: Moussatche
authors.forename: Steven T
authors.initials: ST
authors.lastname: Lund
authors.forename: Jeffery B
authors.initials: JB
authors.lastname: Jones
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Klee
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000382:microbiology*; D003517:Cyclopentanes / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006790:Host-Parasite Interactions; D007210:Indoleacetic Acids / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D054883:Oxylipins; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D016959:Xanthomonas campestris / Q000502:physiology*
chemical_list: D003517:Cyclopentanes; D005030:Ethylenes; D007210:Indoleacetic Acids; D054883:Oxylipins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083750:ethylene receptors, plant; C011006:jasmonic acid; C030737:indoleacetic acid; C036216:ethylene; D006899:Mixed Function Oxygenases; C022619:salicylate 1-monooxygenase; D020156:Salicylic Acid