Plastid signals induce ALTERNATIVE OXIDASE expression to enhance the cold stress tolerance in Arabidopsis thaliana

The external environment affects the metabolic activities of plants, and plastids play an important role in sensing the environmental situation and executing adaptive responses to environmental stresses. Previous studies have indicated that some plastid-signaling deficient mutants have impaired basal thermo-tolerance, drought tolerance, and high-light tolerance. In this study, we investigated the role of plastid signals in alleviating cold stress damage in Arabidopsis (Arabidopsis thaliana). Thermographic analysis revealed that wide-type (Col-0) plants maintained a higher temperature at about 22 A degrees C, whereas the leaf temperature of plastid-signaling deficient mutants was about 18 A degrees C upon 4 A degrees C cold stress. The relative water content of the mutants significantly decreased after cold treatment, whereas H2O2 content, electrolyte leakage, and malonaldehyde content increased compared with Col-0. The cyanide-resistant respiration rates of the mutants were lower than those of wild-type plants. Quantitative real-time PCR analysis revealed that AOX1a (encoding alternative oxidase, a key enzyme for cyanide-resistant respiration) transcripts in the mutants were much lower than wild-type after cold stress. Moreover, investigations with aox1a mutant further indicated that plastid signals enhance plant cold stress tolerance mainly through the induction of AOX1a.