Spz6 Is Essential for Regulating the Immune Response to Escherichia Coli and Staphylococcus Aureus Infection in Tenebrio Molitor.

Spätzle is an extracellular protein that activates the Toll receptor during embryogenesis and immune responses in . However, the functions of the spätzle proteins in the innate immune response against bacteria or fungi in are not well understood. Therefore, in this study, the open reading frame (ORF) of was identified and its function in the response to bacterial and fungal infections in was investigated using RNAi. The highest expression of was in prepupae and in 3- and 6- day-old pupae. While in other stages, remarkable expression was also observed. The tissue-specific expression analysis showed that expression was highest in the hemocytes of larvae. expression was highly induced when challenged with Escherichia coli, Staphylococcus aureus, or Candida albicans at 6 h post-injection; however, silenced larvae were significantly more susceptible to only and infection. The antimicrobial peptides (AMPs) gene expression analysis results show that mainly positively regulated the expression of and in response to E. coli and S. aureus infection. Collectively, these results suggest that TmSpz6 plays an important role in regulating AMP expression and increases the survival of T. molitor against E. coli and S. aureus.