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Update on Reactive Oxygen Species in Chloroplasts Production and Scavenging of Reactive Oxygen Species in Chloroplasts and Their Functions 1
| Content Provider | Semantic Scholar |
|---|---|
| Author | Asada, Kozi |
| Copyright Year | 2006 |
| Abstract | The reaction centers of PSI and PSII in chloroplast thylakoids are the major generation site of reactive oxygen species (ROS). Photoreduction of oxygen to hydrogen peroxide (H2O2) in PSI was discovered over 50 years ago by Mehler (1951). Subsequently, the primary reduced product was identified to be superoxide anion (O2 ), and its disproportionation produces H2O2 and O2 (Asada et al., 1974). On the other hand, in PSII, oxygen of the ground (triplet) state (3O2) is excited to singlet state (1O2) by the reaction center chlorophyll (Chl) of triplet excited state (P680*; Telfer et al., 1994; Hideg et al., 1998). The photoproduction of ROS is largely affected by physiological and environmental factors; the rate is enhanced under the conditions where photon intensity (P) is in excess of that required for the CO2 assimilation (A). Under the conditions of photon excess (P.A), the relaxation systems suppress the photoproduction of ROS in chloroplasts, such as photorespiration, the cyclic electron flows through either PSI or PSII, and the down-regulation of PSII quantum yield as regulated by the xanthophyll cycle and the proton gradient across thylakoid membrane. Prompt scavenging of the ROS produced in thylakoids prior to its diffusion from the generation site is indispensable to protect the target molecules in thylakoid and stroma. Here, the production of reduced and excited species of ROS and their scavenging system in chloroplasts are overviewed. The photoproduction and subsequent scavenging of ROS not only protect chloroplasts from the direct effects of ROS, but also relax the photon (electron) excess stress, and these physiological functions of ROS production and scavenging are discussed. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.plantphysiol.org/content/plantphysiol/141/2/391.full.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
