Poster: Intracellular Signaling

Abs # 838: Differences in spatiotemporal properties of second messenger agonist induced Ca²⁺ release in Tradescantia stamen hair cells and Lilium pollen tubes.

Presenter:	DePass, Anthony L, adepass@liu.edu
Authors	DePass, Anthony L (A)   Wilson, Joshua  (A)   Cardenas, Luis  (B)   Hepler, Peter K (B)
Affiliations:	(A): Long Island University-Brooklyn (B): University of Massachusetts-Amherst

Inositol (1,4,5) trisphosphate (IP₃) and Cyclic ADP-ribose (CADPR) are known agonists that participate in second messenger signal transduction pathways by mediating Ca²⁺ release from intracellular stores. Studies in animal cells have shown a variety in spatiotemporal properties of intracellular Ca²⁺ release due to the action of these agonists. We microinjected Tradescantia stamen hair cells and Lilium pollen tubes with the radiometric fluorescent dye fura-2 conjugated to dextran (10kd) and measured cytosolic [Ca²⁺] after iontophoretic injection of IP₃, CADPR and its precursor NAD⁺. Our observations in Tradescantia indicate that Ca²⁺ release was concentrated in the cortical and perinuclear regions of the cell with little evidence of release from the central vacuole. Furthermore, CADPR mediated Ca²⁺ release progressed from the point of injection along the cortical region to the perinuclear area in what appears to be a Ca²⁺ induced Ca²⁺ release mechanism with the culminating perinuclear release only occurring only if an initial “threshold” level of [Ca²⁺] was attained at injection. Injections in Lilium pollen tubes resulted in recurrent longitudinal calcium waves emanating from the point of injection after a delay of five to ten seconds. The waves were successively smaller with diminution after 3-5 episodes. We were unable to differentiate the source (ER vs. vacuole) of Ca²⁺ release in the pollen tube. Supported by the National Science Foundation MCB#0077599