AUTHOR=Park Soyi , Jo Yong Hun , Park Ki Beom , Ko Hye Jin , Kim Chang Eun , Bae Young Min , Kim Bobae , Jun Sung Ah , Bang In Seok , Lee Yong Seok , Kim Yu Jung , Han Yeon Soo 

TITLE=TmToll-7 Plays a Crucial Role in Innate Immune Responses Against Gram-Negative Bacteria by Regulating 5 AMP Genes in Tenebrio molitor

JOURNAL=Frontiers in Immunology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2019.00310

DOI=10.3389/fimmu.2019.00310

ISSN=1664-3224

ABSTRACT=<p>Although it is known that the <italic>Drosophila</italic> Toll-7 receptor plays a critical role in antiviral autophagy, its function in other insects has not yet been reported. Here, we have identified a Toll-like receptor 7 gene, <italic>TmToll-7</italic>, in the coleopteran insect <italic>T. molitor</italic> and examined its potential role in antibacterial and antifungal immunity. We showed that <italic>TmToll-7</italic> expression was significantly induced in larvae 6 h after infection with <italic>Escherichia coli</italic> and <italic>Staphylococcus aureus</italic> and 9 h after infection with <italic>Candida albicans</italic>. However, even though <italic>TmToll-7</italic> was induced by all three pathogens, we found that <italic>TmToll-7</italic> knockdown significantly reduced larval survival to <italic>E. coli</italic>, but not to <italic>S. aureus</italic>, and <italic>C. albicans</italic> infections. To understand the reasons for this difference, we examined the effects of <italic>TmToll-7</italic> knockdown on antimicrobial peptide (AMP) gene expression and found a significant reduction of <italic>E. coli</italic>-induced expression of AMP genes such as <italic>TmTenecin-1, TmDefensin-1, TmDefensin-2, TmColeoptericin-1</italic>, and <italic>TmAttacin-2</italic>. Furthermore, <italic>TmToll-7</italic> knockdown larvae infected with <italic>E. coli</italic> showed significantly higher bacterial growth in the hemolymph compared to control larvae treated with <italic>Vermilion</italic> dsRNA. Taken together, our results suggest that TmToll-7 plays an important role in regulating the immune response of <italic>T. molitor</italic> to <italic>E. coli</italic>.</p>