Poster: Late and Moved Abstracts

Abs # 1432: Extracellular ATP acts as a potential signaling molecule in controlling growth and development in Arabidopsis

Presenter:	Tang, Wenqiang , tangwq@mail.utexas.edu
Authors	Tang, Wenqiang  (A)   Jeter, Collene  (A)   Henaff, Elizabeth  (A)   Stout, Stephen  (A)   Roux, Stanley  (A)
Affiliations:	(A): University of Texas at Austin

ATP and ADP are well known extracellular signaling molecules in animals, where they bind to specialized P2-receptors and trigger signaling cascades that lead to diverse responses. Although no genomic sequence in Arabidopsis has been found that is obviously similar to the described animal purinoceptors, apyrases, enzymes important for quenching the extracellular ATP/ADP signal in animals, have been found in Arabidopsis. This raises the possibility that extracellular ATP may also serve a regulatory role in plants. Here we report that the stimuli of cold, touch and osmotic shock can stimulate ATP release from plant cells. ATP-g-S and ADP-b-S, two non-degradable ATP/ADP analogs which are often used as P2-receptor agonists, both stimulate an increase in [Ca2+]_cyt when applied exogenously, as measured in apo-aequorin transgenic Arabidopsis. Significant increases in [Ca2+]_cyt are induced by mM-mM levels of ATP-g-S and ADP-b-S in a dose-dependent fashion, but not by AMP-S controls. Exogenously applied 0.5 mM ATP-g-S can also regulate gene expression as judged by DNA microarray and Northern analysis. Arabidopsis seedlings grown in media containing 0.1 mM ATP-g-S for one week in darkness show enhanced hypocotyl growth relative to controls, but if the media concentration is raised to 1 mM, hypocotyl growth is inhibited. The [ATP] released at wound sites approaches 0.2 mM or higher, i.e., near to or above the level needed to induce the responses reported here. Taken together, our results strongly suggest that extracellular ATP is a potential signaling molecule in regulating the growth and development of plant cells.