Cytochrome respiration pathway and sulphur metabolism sustain stress tolerance to low temperature in the Antarctic species Colobanthus quitensis.

-Understanding the strategies employed by plant species that live in extreme environments offers the possibility to discover stress tolerance mechanisms. We studied the physiological, antioxidant and metabolic responses to three temperature conditions (4, 15 and 23ºC) of Colobanthus quitensis (CQ), one of the only two native vascular species in Antarctica. We also employed Dianthus chinensis (DC), to asssess the effects of the treatments in a non-antarctic species from the same family. -Using fused LASSO modeling we associated physiological and biochemical antioxidant responses with primary metabolism. This approach allowed us to highlight the metabolic pathways driving the response specific to CQ. -Low temperature imposed dramatic reductions in photosynthesis (up to 88%) but not in respiration (sustaining rates of 3.0-4.2 µmol CO₂ m^-2 s^-1 ) in CQ, and any change in the physiological stress parameters was found. Its notable antioxidant capacity and mitochondrial cytochrome respiratory activity (20 and 2 times higher than DC, respectively) which ensure ATP production even at low temperature, was significantly associated to sulphur-containing metabolites and polyamines. -Our findings potentially open new biotechnological opportunities regarding the role of antioxidant compounds and respiratory mechanisms associated to sulphur metabolism in stress tolerance strategies to low temperature. This article is protected by copyright. All rights reserved.