Identification and functional analysis of mitochondrial protein-coding genes associated with the adaptability to cold stress of the rusty grain beetle Cryptolestes ferrugineus

Insects enhance the adaptability to extreme environments by regulating oxidative phosphorylation processes and therefore ATP synthesis rates. The mitochondrial protein-coding genes (PCGs) are involved in energy metabolism and essential for regulating various physiological processes in environmental adaptability of insects. In this study, we found the cold tolerance of Cryptolestes ferrugineus was significantly increased after the acclimation to different low temperatures. Besides, the cold acclimation can lead to the significant decreasing in metabolic rates, including respiratory rate and ATP content. Then, a total of 12 mitochondrial PCGs were identified in C. ferrugineus, with 8 mitochondrial PCGs showing the significant down-regulation during cold acclimation. The further functional analysis showed that the knocking down of 2 down-regulated genes, ND4 and COXIII, by RNA interference (RNAi) would result in the enhanced cold tolerance, with the significant inhibition of metabolic rates in C. ferrugineus as well. The present findings suggested that mitochondrial PCGs ND4 and COXIII might be involved in cold tolerance by regulating energy metabolism in C. ferrugineus, which offered us the fundamental insights into the molecular mechanisms of C. ferrugineus adaption to cold stress.