Cloning and characterization of a midgut-specific fatty acid binding protein in Spodoptera litura.

A fatty acid binding protein (FABP) gene (Slfabp1) was cloned from the midgut of Spodoptera litura larvae. The gene consists of four exons and three introns and encodes a peptide of 134 amino acid residues with a predicted molecular mass of 14.7 kDa, which was confirmed by in vitro protein expression. Northern blot and Western blot analyses indicated that both of Slfabp1 mRNA and protein were highly and specifically expressed in the midgut during the fifth and sixth instar feeding larval stages. In situ hybridization and immunohistochemistry analyses confirmed the midgut-specific localization of Slfabp1 mRNA and protein. The result of Western blot showed that expression of the protein was downregulated by starvation and upregulated by refeeding in sixth instar larvae. All of the results taken together suggest that the SlFABP1 plays important role(s) in FA uptake and transport in the midgut during the larval feeding stages of the insect.