Poster: Signaling, cell-to-cell

Abs # 437: Evidence of a Novel Cell Signaling Role for Extracellular Nucleoside Tri- and Diphosphates in Arabidopsis

Presenter:	Jeter, Collene R., jeterc@mail.utexas.edu
Authors	Jeter, Collene R. (A)   Tang, Wenqiang  (A)   Henaff, Elizabeth  (A)   Roux, Stanley J. (A)
Affiliations:	(A): The University of Texas at Austin

ATP can exit cells and enter the extracellular milieu passively as a result of cell damage, or by active transport mechanisms. Because extracellular ATP is a known receptor agonist in animals and was previously shown to alter plant growth, we investigated whether ATP derivatives could function outside plant cells as signaling agents. Signaling responses induced by exogenous nucleotides in animal cells typically include increases in free cytoplasmic calcium concentration ([Ca²⁺]_cyt). We have evaluated the ability of exogenously applied ATP, ADP and AMP to alter [Ca²⁺]_cyt in the shoot cells of intact Arabidopsis seedlings transformed with the apo-aequorin calcium reporter gene. ATP and ADP increase [Ca²⁺]_cyt above the level needed to activate calcium signaling pathways, and this increase is enhanced further when the nucleotides are added together with the elicitor oligogalacturonic acid. The increase in [Ca²⁺]_cyt in response to ADP can be prevented by calcium-channel blocking agents and by the calcium chelator BAPTA. Additionally, various forms of stress are shown to induce ATP release from whole seedlings into the surrounding medium, and exogenous treatment with ATP increases the level of transcripts encoding multiple proteins known to be upregulated by stress stimuli. These observations suggest that extracellular ATP can activate cell-signaling pathways in plants, potentially playing a physiological role in mediating stress and wound responses.