title: Measurement of stress-induced Ca(2+) pulses in single aequorin-transformed tobacco cells.
abstract: Signaling patterns measured in large cell populations are the sum of differing signals from separate cells, and thus, the detailed kinetics of Ca(2+) pulses can often be masked. In an effort to evaluate whether the cytosolic Ca(2+) pulses previously reported in populations of elicitor- and stress-stimulated tobacco cells accurately represent the pulses that occur in individual cells, a study of single cell Ca(2+) fluxes in stress-stimulated tobacco cells was undertaken. Individual aequorin-transformed cells were isolated from a tobacco suspension culture and placed directly on a sensitive photo-multiplier tube mounted in a dark chamber. Ca(2+)-dependent luminescence was then monitored after stimulation with hypo- or hyper-osmotic shock, cold shock, or defense elicitors (oligogalacturonic acid and harpin). Hypo-osmotic shock induced a biphasic Ca(2+) transient in 67% of the single cells tested that exhibited similar kinetics to the biphasic pulses measured repeatedly in 1ml cell suspensions. In contrast, 33% of the stimulated cells displayed Ca(2+) flux patterns that were not previously seen in cell suspension studies. Additionally, because only 29% of the cells tested responded with measurable Ca(2+) pulses to oligogalacturonic acid and 33% to the harpin protein, we conclude that not all cells in a suspension are simultaneously sensitive to stimulation with defense elicitors. In contrast, all cells tested responded with an immediate Ca(2+) influx after cold or hyperosmotic shock. We conclude that in many cases the Ca(2+) signaling patterns of single cells are accurately represented in the signaling patterns of large populations, but that single cell measurements are still required to characterize the Ca(2+) fluxes of the less prominent cell populations.
authors.affiliation: Program for Biochemistry and Molecular Biology, Purdue University, W. Lafayette, IN 47907, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Cessna
authors.forename: M A
authors.initials: MA
authors.lastname: Messerli
authors.forename: K R
authors.initials: KR
authors.lastname: Robinson
authors.forename: P S
authors.initials: PS
authors.lastname: Low
mesh_terms: D000331:Aequorin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D002513:Cephamycins / Q000494:pharmacology; D003080:Cold Temperature; D008163:Luminescent Measurements; D009844:Oligosaccharides / Q000494:pharmacology; D009997:Osmotic Pressure / Q000187:drug effects; D010947:Plants, Toxic; D012965:Sodium Chloride / Q000494:pharmacology; D014026:Nicotiana / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014170:Transformation, Genetic; D019076:Transgenes / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002513:Cephamycins; D009844:Oligosaccharides; C075462:harpin protein, Erwinia amylovora; C412763:oligogalacturonic acid; C087295:HrpZ protein, Pseudomonas syringae; D012965:Sodium Chloride; D000331:Aequorin; C027446:oganomycins; D002118:Calcium