| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
First published online September 16, 2005; 10.1104/pp.105.066803 Plant Physiology 139:935-948 (2005) © 2005 American Society of Plant Biologists
Cauliflower mosaic virus, a Compatible Pathogen of Arabidopsis, Engages Three Distinct Defense-Signaling Pathways and Activates Rapid Systemic Generation of Reactive Oxygen Species1Plant Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom (A.J.L., V.L., J.J.M.); and School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom (B.W.Y., G.J.L.)
We analyzed expression of marker genes for three defense pathways during infection by Cauliflower mosaic virus (CaMV), a compatible pathogen of Arabidopsis (Arabidopsis thaliana), using luciferase reporter transgenes and directly by measuring transcript abundance. Expression of PR-1, a marker for salicylic acid signaling, was very low until 8 d postinoculation and then rose sharply, coinciding with the rise in virus levels. In contrast, as early as 2 h postinoculation, transcriptional up-regulation of GST1—a marker for reactive oxygen species—and PDF1.2—a marker for jasmonic acid/ethylene defense signaling—was detectable in the virus-inoculated leaf and systemically. In parallel with the activation of GST1, H2O2 accumulated locally and systemically in virus- but not mock-inoculated plants. However, in plants inoculated with infectious CaMV DNA rather than virus particles, the onset of systemic luciferase activity was delayed by 24 to 48 h, suggesting that virion structural proteins act as the elicitor. This phenomenon, which we term the rapid systemic response, preceded virus movement from the inoculated leaf; therefore, the systemic signal is not viral. Systemic, but not local, H2O2 accumulation was abolished in rbohDF double mutants and in etr1-1 and ein2-1 mutants, implicating NADPH oxidase and ethylene signaling in the generation and transduction of the response. Ethylene, but not rbohDF mutants, also showed reduced susceptibility to CaMV, whereas in NahG transgenics, virus levels were similar to wild type. These findings implicate reactive oxygen species and ethylene in signaling in response to CaMV infection, but suggest that salicylic acid does not play an effective role.
1 This work was supported in part by the Biotechnology and Biological Sciences Research Council (BBSRC; grant nos. 17P/09461, 17P/12855, and 15/P20067 to J.J.M., grant no. 17/P12855 to V.L., and grant no. 15/P20067 to G.J.L.). A.J.L. was the recipient of an Institute of Biological and Life Sciences postgraduate studentship and was supported for the later part of the work by the Bower Fire Insurance Fund. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.066803. * Corresponding author; e-mail joel.milner{at}bio.gla.ac.uk; fax 44–141–330–4447. Received June 10, 2005; returned for revision June 10, 2005; accepted June 30, 2005. This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ASPB Publications | PLANT PHYSIOLOGY® | THE PLANT CELL | |
|---|---|---|---|
