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- Title
Seven-up facilitates insect counter-defense by suppressing cathepsin B expression.
- Authors
Ahn, Ji-Eun; Guarino, Linda A.; Zhu-Salzman, Keyan
- Abstract
When challenged by the dietary soybean cysteine protease inhibitor scN, the cowpea bruchid ( Callosobruchus maculatus) adapts to the inhibitory effects by readjusting the transcriptome of its digestive system, including the specific activation of a cathepsin B-like cysteine protease CmCatB. To understand the transcriptional regulation of CmCatB, we cloned a portion of its promoter and demonstrated its activity in Drosophila cells using a chloramphenicol acetyltransferase reporter system. EMSAs detected differential DNA-binding activity between nuclear extracts of scN-adapted and -unadapted midguts. Two tandem chicken ovalbumin upstream promoter ( COUP) elements were identified in the CmCatB promoter that specifically interacted with a protein factor unique to nuclear extracts of unadapted insect guts, where CmCatB expression was repressed. Seven-up (Svp) is a COUP-TF-related transcription factor that interacted with the COUP responsive element. Polyclonal anti-(mosquito Svp) serum abolished the specific DNA-binding activity in cowpea bruchid midgut extracts, suggesting that the protein factor is an Svp homolog. Subsequent cloning of a cowpea bruchid Svp (CmSvp) indicated that it shares a high degree of amino acid sequence similarity with COUP-TF/Svp orphan nuclear receptor family members from varied species. The protein was more abundant in scN-unadapted insect guts than scN-adapted guts, consistent with the observed DNA-binding activity. Furthermore, CmCatB expression was repressed when CmSvp was transiently expressed in Drosophila cells, most likely through COUP binding. These findings indicate that CmSvp may contribute to insect counter-defense, in part by inhibiting CmCatB expression under normal growth conditions, but releasing the inhibition when insects are challenged by dietary protease inhibitors.
- Subjects
COWPEA weevil; LEGUME diseases &; pests; PROTEASE inhibitors; DROSOPHILA; FRUIT flies; TRANSCRIPTION factors
- Publication
FEBS Journal, 2007, Vol 274, Issue 11, p2800
- ISSN
1742-464X
- Publication type
Article
- DOI
10.1111/j.1472-4658.2007.05816.x