Analysis of the Toll and Spaetzle Genes Involved in Toll Pathway-Dependent Antimicrobial Gene Induction in the Red Flour Beetle, <i>Tribolium castaneum</i> (Coleoptera; Tenebrionidae)
Insects rely only on their innate immune system to protect themselves from pathogens. Antimicrobial peptide (AMP) production is the main immune reaction in insects. In <i>Drosophila melanogaster</i>, the reaction is regulated mainly by the Toll and immune deficiency (IMD) pathways. Spaet...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-01-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/24/2/1523 |
| Summary: | Insects rely only on their innate immune system to protect themselves from pathogens. Antimicrobial peptide (AMP) production is the main immune reaction in insects. In <i>Drosophila melanogaster</i>, the reaction is regulated mainly by the Toll and immune deficiency (IMD) pathways. Spaetzle proteins, activated by immune signals from upstream components, bind to Toll proteins, thus, activating the Toll pathway, which in turn, induces AMP genes. Previous studies have shown the difference in immune systems related to Toll and IMD pathways between <i>D. melanogaster</i> and <i>Tribolium castaneum</i>. In <i>T. castaneum</i>, nine Toll and seven spaetzle (spz) genes were identified. To extend our understanding of AMP production by <i>T. castaneum</i>, we conducted functional assays of Toll and spaetzle genes related to Toll-pathway-dependent AMP gene expression in <i>T. castaneum</i> under challenge with bacteria or budding yeast. The results revealed that <i>Toll3</i> and <i>Toll4</i> double-knockdown and <i>spz7</i> knockdown strongly and moderately reduced the Toll-pathway-dependent expression of AMP genes, respectively. Moreover, <i>Toll3</i> and <i>Toll4</i> double-knockdown pupae more rapidly succumbed to entomopathogenic bacteria than the control pupae, but <i>spz7</i> knockdown pupae did not. The results suggest that <i>Toll3</i> and <i>Toll4</i> play a large role in Toll-pathway-dependent immune reactions, whereas <i>spz7</i> plays a small part. |
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| ISSN: | 1661-6596 1422-0067 |