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Unformatted text preview: INTRODUCTION Plant mitochondria are different from those of animals as their electron transport chain contains a number of com- ponents that enable non-coupled respiration. Among them, the best characterized is the cyanide-resistant alternative terminal oxidase (AOX), a homodimeric di- iron protein, which transfers electrons via an alternative pathway from the ubiquinone pool directly to oxygen. 1 Because the alternative pathway branches in electron transport at the ubiquinone pool, its contribution to energy balance is one-third that of the cytochrome path- way. The physiological role of such a ‘wasteful’ respira- tory pathway has been linked to thermogenesis during anthesis in arum lilies, 2 and has been suggested to oper- ate as a passive overflow mechanism under conditions where the cytochrome chain is restricted, 3 or function to prevent reactive oxygen species (ROS) formation pro- duced as a result of impaired or restricted respiratory activity. 3,4 © W. S. Maney & Son Ltd Redox Report , Vol. 10, No. 2, 2005 DOI 10.1179/135100005X21688 Research article The maize alternative oxidase 1a ( Aox1a ) gene is regulated by signals related to oxidative stress Alexios N. Polidoros 1 , Photini V. Mylona 2 , Konstantinos Pasentsis 1 , John G. Scandalios 3 , Athanasios S. Tsaftaris 1,4 1 Institute of Agrobiotechnology, Center for Research and Technology Hellas, Thermi, Greece 2 Agricultural Research Center of Macedonia-Thrace, NAGREF, Thermi, Greece 3 Department of Genetics, North Carolina State University, Raleigh, North Carolina, USA 4 Department of Genetics and Plant Breeding, Aristotle University of Thessaloniki, Thessaloniki, Greece We isolated and characterized the expression of Aox1a , a member of the maize alternative oxidase ( Aox ) small multigene family. Aox1a consists of four exons interrupted by three introns and its promoter harbors diverse stress-specific putative regulatory motifs pointing to complex regulation and response to multiple signals. Responses of Aox1a to such signals were examined and compared with those of maize glutathione S-transferase I ( GstI ), a typical oxidative stress inducible gene. Potassium cyanide (KCN) and hydrogen peroxide (H 2 O 2 ) induced a rapid increase of the Aox1a and GstI transcripts, which was persisted in prolonged treatment at high H 2 O 2 concentration only for Aox1a . High concentration of salicylic acid (SA) and salicyl hydroxamic acid (SHAM) induced Aox1a mRNA only after prolonged exposure, while GstI displayed an early strong induction, which declined thereafter. Nitric oxide (NO) induced a high increase of Aox1a after prolonged exposure at high concentration, while GstI displayed a weak response. Our results show that multiple signaling pathways, involved in stress responses, also participate and differentially regulate Aox1a and GstI in maize. A ROS-depended signaling event may be involved, suggesting an essential role of Aox1a under oxidative stress in maize....
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This note was uploaded on 09/13/2010 for the course DGPB 024e taught by Professor Alexiospolidoros during the Spring '10 term at Aristotle University of Thessaloniki.
- Spring '10