Effect of cold stress on oxidative damage and mitochondrial respiratory properties in chickpea

The present work aimed to characterize some of the mitochondrial and defense responses involved in tolerance to cold stress (CS) in tolerant (Sel96Th11439) and sensitive (ILC533) chickpea (Cicer arietinum L.) genotypes. During CS, the tolerant genotype prevented the H₂O₂ accumulation significantly; led to a decrease in electrolyte leakage index (ELI), which was a sign of relative acclimation of this genotype compared to sensitive one. A significant positive correlation between ELI and H₂O₂ (r_0.01 = 0.86) content confirmed these results. Under cold, a significant increase in the alternative oxidase (AOX) activity was observed in tolerant genotype compared to sensitive one. In parallel, the high activity of superoxide dismutase (SOD) accompanied with catalase (CAT) and ascorbate peroxidase (APX) activities and also the extreme amounts of ascorbate and proline certified the active reactive oxygen species (ROS)-scavenging systems. There was a significant negative correlation between damage indices like H₂O₂ content and the activity of AOX (r_0.01 = -0.79) as well as significant positive correlation between AOX activity with CAT (r_0.05 = 0.61), SOD (r_0.05 = 0.51) and APX activity (r_0.05 = 0.52). The increasing succinate dehydrogenase (CaSDH), CaAOX and cytochrome c oxidase (CaCOX) gene expression showed an enhancing response of respiration under CS in tolerant plants compared to sensitive ones. The increasing trend of phosphoenol pyruvate carboxylase (PEPC) activity in tolerant genotype particularly in the sixth day of CS indicated the recovered performance of metabolism pathways. Therefore, the increase of AOX activity along with other defensive mechanisms could be coordinately related to cold tolerance mechanisms in order to alleviate cold-induced oxidative stress in chickpea.