Mitochondrial Respiration: Involvement of the Alternative Respiratory Pathway and Residual Respiration in Abiotic Stress Responses

CHOCOBAR PONCE SILVANA; PRADO CAROLINA DEL VALLE; GONZALEZ ROSANA; ROSA MARIANA DANIELA; PRADO FERNANDO EDUARDO

Physiological Mechanisms and Adaptation Strategies in Plants Under Changing Environment

Springer

Lugar: New York; Año: 2014; p. 367 - 432

Mitochondrial respiration provides energy necessary to drive the cellular metabolism in all living organisms. From ubiquinone mitochondrial respiratory electron transport chain (ETC) of plants, many fungi and protozoans branches into cyanide-sensitive and cyanide-insensitive pathways. The first one named cytochrome pathway (CP) used cytochrome c oxidase (COX) as terminal oxidase while the second, named alternative pathway (AP) utilizes an alternative oxidase (AOX) as terminal oxidase. COX reduces O2 to H2O and is couples to H+?gradient generation used to make ATP. AOX reduces O2 upon oxidation of ubiquinol (UQH2) without coupling to ATP production. Despite its role as energy-dissipating pathway, AP also plays a key role in coordinated responses of cells to both abiotic and biotic stresses. In this context, when effectiveness of CP becomes limited by stress condition, AP allows a stress-dependent flexibility of respiratory electron transport chain leading to an enhanced fitness of stressed plants. Residual respiration (Rresp), insensitive to cyanide and salicylhydroxamic acid (SHAM), no mediated neither by CP or AP, also occurs in living plants. Although nature of this unique respiration is unknown, some new evidences seem to suggest that it plays an important role in abiotic stress responses. Thus, it is becoming clear that both AP, through the AOX activity, and Rresp, constitute key components of orchestrated mitochondrial events, occurring in plants exposed to unfavourable environmental conditions.