Knockdown of Dorsal switch protein 1 Effect on Growth, Development, and survivability of Tenebrio molitor (Coleoptera: Tenebrionidae)

Dorsal switch protein 1 (DSP1) of insects and high mobility group box 1 (HMGB1) protein of vertebrates are homologous. Both HMGB1 and DSP1 act as damage-associated molecular pattern (DAMP) molecules. Previous studies reported that DSP1 plays a DAMP role in mealworm, Tenebrio molitor, by activating immune genes like antimicrobial peptides (AMPs), phospholipase A₂ (PLA₂), phenoloxidase (PO) and regulating nodulation. However, RNAi of Tm-DSP1 suppresses these genes and their immune responses. While the immune role of DSP1 is established, its function in growth, development and survivability of T. molitor larvae is unknown. This study was designed to assess the role of DSP1 in the above-mentioned aspects. Tm-DSP1 gene was expressed in all the developmental stages and tissues of T. molitor larvae. The highest expression was observed in L6 larval stage and fat body tissue. Tm-DSP1 detection by western blotting supports its expression in T. molitor samples. Following bacterial challenge, DSP1 expression was upregulated in immune-related tissues, including hemocyte, fat body, and midgut. Detection of increased DSP1 in bacteria-challenged plasma ensures the release of DSP1 in plasma from the cell nucleus of immune-challenged larvae. Additionally, RNAi knockdown of Tm-DSP1 led to reduced larval growth (body length) and development (body weight) of T. molitor larvae resulting in increased mortality of the larvae. These findings suggest that DSP1 regulates the growth, development, and survival of T. molitor. However, whether DSP1 directly plays a role in these physiological processes or whether it interrupts any other genes to achieve these effects is still unknown. Further study is required to clarify this issue.