Cold and Heat Stress Diversely Alters Both

Complex proteomic and physiological approaches to study cold and heat stress 17 responses in plant mitochondria are still limited. Variations in the mitochondrial proteome of 18 cauliflower (Brassica oleracea var. botrytis) curds after cold and heat and after stress recovery were 19 assayed by 2D PAGE in relation to respiratory parameters. Quantitative analysis of the 20 mitochondrial proteome revealed numerous stress-affected protein spots. In cold alternative 21 oxidase isoforms were extensively upregulated; major downregulations in the level of 22 photorespiratory enzymes, porine isoforms, oxidative phosphorylation (OXPHOS) and some 23 low-abundant proteins were observed. On the contrary, distinct proteins, including carbohydrate 24 metabolism enzymes, heat-shock proteins, translation, protein import, and OXPHOS components 25 were involved in heat response and recovery. Few metabolic regulations were suggested. 26 Cauliflower plants appeared less susceptible to heat; closed stomata in heat stress resulted in 27 moderate photosynthetic, but only minor respiratory impairments, however photosystem II 28 performance was unaffected. Decreased photorespiration corresponded with proteomic alterations 29 in cold. Our results show that cold and heat stress not only operate in diverse mode (exemplified 30 by cold-specific accumulation of some heat shock proteins), but exert some associations on 31 molecular and physiological levels. This implies more complex model of action of investigated 32 stresses on plant mitochondria. 33