Identification and expression profile of a putative basement membrane protein gene in the midgut of Helicoverpa armigera

BACKGROUND: The midgut undergoes histolysis and remodeling during the larval to adult transition in holometabolous insects, but the molecular mechanisms underlying this process are not well understood. RESULTS: Using Suppression Subtractive Hybridization (SSH), we identified a 531 bp cDNA predicted to encode a 176 amino acid protein, which we call hmg176. Northern and western blot analysis suggested that high levels of hmg176 are expressed in the midgut during molting, but not during metamorphosis. HMG176 protein was detected by immunofluorescence within the membrane of fat bodies and the basement membrane of the midgut of both molting and feeding larvae, but not in metamorphically committed larvae. In situ hybridization revealed that hmg176 transcripts mainly localized to the columnar cells of the midgut. Interestingly, a non-steroidal ecdysone agonist, RH-2485, significantly upregulated expression of hmg176. CONCLUSION: These observations suggest that hmg176 encodes a larval-specific protein that may participate in sustaining larval midgut during larval development, possibly in response to ecdysteroid in vivo. This study will enlighten our understanding of the molecular mechanisms of tissue histolysis during metamorphosis.