Light and oxygen are not required for harpin-induced cell death.
Nicotiana sylvestris leaves challenged by the bacterial elicitor harpin N(Ea) were used as a model system in which to determine the respective roles of light, oxygen, photosynthesis, and respiration in the programmed cell death response in plants. The appearance of cell death markers, such as membrane damage, nuclear fragmentation, and induction of the stress-responsive element Tnt1, was observed in all conditions. However, the cell death process was delayed in the dark compared with the light, despite a similar accumulation of superoxide and hydrogen peroxide in the chloroplasts. In contrast, harpin-induced cell death was accelerated under very low oxygen (<0.1% O(2)) compared with air. Oxygen deprivation impaired accumulation of chloroplastic reactive oxygen species (ROS) and the induction of cytosolic antioxidant genes in both the light and the dark. It also attenuates the collapse of photosynthetic capacity and the respiratory burst driven by mitochondrial alternative oxidase activity observed in air. Since alternative oxidase is known to limit overreduction of the respiratory chain, these results strongly suggest that mitochondrial ROS accumulate in leaves elicited under low oxygen. We conclude that the harpin-induced cell death does not require ROS accumulation in the apoplast or in the chloroplasts but that mitochondrial ROS could be important in the orchestration of the cell suicide program.
Garmier
Marie
M
Institut de Biotechnologie des Plantes, Université Paris-Sud 11, UMR-CNRS 8618, Bâtiment 630, 91405, Orsay Cedex, France.
Priault
Pierrick
P
Vidal
Guillaume
G
Driscoll
Simon
S
Djebbar
Reda
R
Boccara
Martine
M
Mathieu
Chantal
C
Foyer
Christine H
CH
De Paepe
Rosine
R
D000975:Antioxidants / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D016923:Cell Death; D002467:Cell Nucleus / Q000378:metabolism; D004573:Electrolytes; D006861:Hydrogen Peroxide / Q000737:chemistry; D008027:Light; D008954:Models, Biological; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D018521:Plant Physiological Phenomena; D017382:Reactive Oxygen Species; D013481:Superoxides / Q000737:chemistry; D014026:Nicotiana / Q000378:metabolism*
D000975:Antioxidants; D004573:Electrolytes; D017382:Reactive Oxygen Species; D013481:Superoxides; D002245:Carbon Dioxide; D006861:Hydrogen Peroxide; D010100:Oxygen