Poster: Signaling, cell-to-cell

Abs # 450: Extracellular nucleotide signaling induces the accumulation of superoxide in Arabidopsis thaliana

Presenter:	Roux, Stanley J, sroux@uts.cc.utexas.edu
Authors	Song, Charlotte  (A)   Stout, Stephen  (A)   Roux, Stanley J (A)
Affiliations:	(A): University of Texas at Austin

Extracellular ATP (xATP) is a well-characterized signaling molecule in animals. It can bind to P2 receptors and induce the production of reactive oxygen species in a response known as the respiratory burst. Recent evidence shows that xATP and xADP may also be signaling molecules in plants, inducing membrane depolarization and calcium increases. We have found that in Arabidopsis thaliana xATP and xADP induce the accumulation of superoxide in a dose-dependent manner, with significant accumulation induced by 1 µM and the peak accumulation occurring at 50 µM ATP. A similar [xAMP] does not induce the same superoxide response. An [ATP] > 15 µM can be found in intercellular spaces at wound sites. Arabidopsis leaves of mutant plants that are disrupted in AtrbohD and AtrbohF, two genes that encode NADPH oxidase homolog subunits, do not show significant superoxide accumulation in response to xATP. DPI, an inhibitor of NADPH oxidase, significantly reduces the accumulation of superoxide induced by xATP. These data suggest that xATP induces the accumulation of superoxide through the activity of NADPH oxidase homologs, AtrbohD and AtrbohF. xATP also induces the accumulation of the transcripts for several genes associated with stress responses in plants, including AtrbohD, LOX2 and ACS6. The latter two genes suggest the possible involvement of ethylene and jasmonic acid in xATP-induced signaling. Moreover, xATP induces increased transcript levels for PAL1, a known defense-response gene that is induced by reactive oxygen species in plants. Thus, xATP induces both superoxide accumulation and changes in gene expression known to be downstream of the superoxide signal. Supported by NSF IBN-0080363 to SJR.