title: Cell death of barley aleurone protoplasts is mediated by reactive oxygen species.
abstract: The barley aleurone layer is a terminally differentiated secretory tissue whose activity is hormonally controlled. The plant hormone gibberellic acid (GA) stimulates the secretion of hydrolytic enzymes and triggers the onset of programmed cell death (PCD). Abscisic acid (ABA) antagonizes the effects of GA and inhibits enzyme secretion and PCD. Reactive oxygen species (ROS) are key players in many types of PCD, and data presented here implicate ROS in hormonally regulated death of barley aleurone cells. Incubation of aleurone layers or protoplasts in H(2)O(2)-containing media results in death of GA-treated but not ABA-treated aleurone cells. Cells that are programmed to die are therefore less able to withstand ROS than cells that are programmed to remain alive. Illumination of barley aleurone protoplasts with blue or UV-A light results in a rapid increase in intracellular H(2)O(2) production. GA-treated protoplasts die rapidly in response to this increase in intracellular H(2)O(2) production, but ABA-treated protoplasts do not die. The rate of light-induced death could be slowed by antioxidants, and incubating protoplasts in the dark with the antioxidant butylated hydroxy toluene reduces the rate of hormonally induced death. Taken together, these data demonstrate that GA-treated aleurone protoplasts are less able than ABA-treated protoplasts to tolerate internally generated or exogenously applied H(2)O(2), and strongly suggest that ROS are components of the hormonally regulated cell death pathway in barley aleurone cells.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA. pcbethke@nature.berkeley.edu
authors.forename: P C
authors.initials: PC
authors.lastname: Bethke
authors.forename: R L
authors.initials: RL
authors.lastname: Jones
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004229:Dithiothreitol / Q000494:pharmacology; D005875:Gibberellins / Q000494:pharmacology; D001467:Hordeum / Q000166:cytology* / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D008027:Light; D010937:Plant Growth Regulators / Q000494:pharmacology; D011523:Protoplasts / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D005875:Gibberellins; D010937:Plant Growth Regulators; D017382:Reactive Oxygen Species; D002084:Butylated Hydroxytoluene; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; C007842:gibberellic acid; D004229:Dithiothreitol