Characterization of the Cap ‘n’ Collar Isoform C gene in Spodoptera frugiperda and its Association with Superoxide Dismutase

Nuclear factor erythroid 2 related factor 2 (Nrf2) belongs to the cap ‘n’ collar basic region leucine zipper (CNC-bZIP) transcription factor family, and is activated by diverse oxidants, pro-oxidants, antioxidants, and chemo-preventive agents. Transcriptional regulation of a battery of detoxifying and antioxidant genes by Nrf2 has been shown to be important for protection against oxidative stress or chemically-induced cellular damages. In our research, we cloned the full length CncC gene from the Spodoptera frugiperda, named as SfCncC. The cDNA of the SfCncC consists of 2652 nucleotides that include a 2196-nucleotide open reading frame (ORF), encoding 731 amino acid residues, and 239- and 217-bp non-coding regions flanking at the 5’- and 3’-ends of the cDNA, respectively. Sequence analysis indicated SfCncC has the conserved domain (CNC-bZIP domain and a tetrapeptide motif, ETGE) character of Nrf2 and showed high identity compared with the CncC/Nrf2 from other insect and vertebrate species. Over-expression of SfCncC can up-regulate the transcription and activity of the SOD gene in Sf9 cells, and the RNAi of SfCncC in Sf9 cells and larvae of S. frugiperda can dramatically reduce the transcriptional level and activity of the SOD gene, as determined by real-time quantitative PCRs. So the SfCncC is involved in the Keap1-Nrf2-ARE pathway, acting the same as the transcriptional factor Nrf2 in vertebrate, and plays a role for host cell defense. The functional characterization of SfCncC provides the fundamental basis for us to further understand the regulatory mechanism of anti-oxidants and anti-xenobiotics in S. frugiperda.