Abstract
Insects can rapidly adapt to environmental changes through physiological responses. The red flour beetle Tribolium castaneum is widely used as a model insect species. However, the stress–response system of this species remains unclear. Superoxide dismutase 2 (SOD2) is a crucial antioxidative enzyme that is found in mitochondria. T. castaneum SOD2 (TcSOD2) is composed of 215 amino acids, and has an iron/manganese superoxide dismutase domain. qRT-PCR experiments revealed that TcSOD2 was present through all developmental stages. To evaluate TcSOD2 function in T. castaneum, we performed RNAi and also assessed the phenotype and antioxidative tolerance of the knockdown of TcSOD2 by exposing larvae to paraquat. The administration of paraquat resulted in significantly higher 24-h mortality in TcSOD2 knockdown larval groups than in the control groups. The TcSOD2 knockdown adults moved significantly more slowly, had lower ATP content, and exhibited a different body color from the control groups. We found that TcSOD2 dsRNA treatment in larvae resulted in increased expression of tyrosinase and laccase2 mRNA after 10 days. This is the first report showing that TcSOD2 has an antioxidative function and demonstrates that T. castaneum may use an alternative antioxidative system when the SOD2-based system fails.
Highlights
Brassicae[8,9], protecting the insect’s body against photooxidative stress[10,11]
We confirmed the sequence of TcSOD2 through cDNA cloning, which deduced that the open reading frame was 648 nucleotides long, encoding a protein of 215 amino acids, a molecular weight of 23,642 Da, and a putative isoelectric point of 8.21
We examined the function of TcSOD2 in T. castaneum
Summary
Brassicae[8,9], protecting the insect’s body against photooxidative stress[10,11]. Various types of antioxidant proteins have been found that regulate the generation of ROS in the body, such as heat shock proteins, superoxide dismutase, DJ-1, and mitogen-activated protein kinase[12,13,14,15,16], all of which are conserved among species. Insects employ the diverse strategies for resistance from environmental stressors. As a result, they are well adapted to environmental change. We were interested in understanding what process T. castaneum beetles employ to eliminate ROS from their bodies, as well as the mechanisms by which they adapt to environmental change. It has been shown that TcSOD1 responds to some type of stress[22], and TcSOD3 is found in T. castaneum, its function remains unclear[23]. It is possible that TcSOD2 might be present in the mitochondrial matrix, as occurs in other species and may respond to oxidative stress[24]. We investigated the function and characteristics of TcSOD2 using RNAi. We evaluated the function of TcSOD2 under oxidative stress using paraquat. We found that TcSOD2 has an antioxidative function and that T. castaneum may have an alternative antioxidative system that can function when the SOD2-based system fails
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