title: Gibberellic acid and abscisic acid coordinately regulate cytoplasmic calcium and secretory activity in barley aleurone protoplasts.
abstract: The effects of gibberellic acid (GA3) and abscisic acid (ABA) on the temporal and spatial dynamics of cytosolic calcium concentration ([Ca2+]i) in aleurone protoplasts of barley (Hordeum vulgare L. cv. Himalaya) were measured by using fluorescence ratio analysis and confocal microscopy. After 4-6 h of treatment, GA3 induced a sustained increase in [Ca2+]i from 50 to 150 nM in aleurone protoplasts. The increase in [Ca2+]i preceded the GA3-induced increase in alpha-amylase synthesis and secretion by 4 h. The elevation of [Ca2+]i was highest in the peripheral cytoplasm and may play a role in coordinating the secretory events there. Reducing Ca2+ levels in the incubation medium to below 500 microM inhibited the increase in [Ca2+]i and the GA3-induced stimulation of alpha-amylase synthesis and secretion. These data suggest that GA3 may increase [Ca2+]i by increasing the influx of Ca2+ at the plasma membrane. ABA reversed the effect of GA3 on [Ca2+]i within 3 h, 2 h before its effect on alpha-amylase production could be detected. Thus changes in [Ca2+]i may play a role in mediating the effects of GA3 and ABA on the synthesis and secretion of alpha-amylase in the aleurone cell.
authors.affiliation: Department of Plant Biology, University of California, Berkeley 94720.
authors.forename: S
authors.initials: S
authors.lastname: Gilroy
authors.forename: R L
authors.initials: RL
authors.lastname: Jones
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000814:Aniline Compounds; D002458:Cell Fractionation; D005456:Fluorescent Dyes; D005875:Gibberellins / Q000494:pharmacology*; D001467:Hordeum / Q000378:metabolism*; D007211:Indoles; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010940:Plant Proteins / Q000096:biosynthesis; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; D005456:Fluorescent Dyes; D005875:Gibberellins; D007211:Indoles; D010940:Plant Proteins; D013462:Sulfur Radioisotopes; D014966:Xanthenes; C059715:Fluo-3; D000040:Abscisic Acid; D008715:Methionine; C007842:gibberellic acid; C048960:indo-1