The protease-based compensatory mechanism to minimize the effect of dietary Soybean Trypsin Inhibitor in Litopenaeus vannamei

Soybean meal is a recurrent ingredient in shrimp feed formulations; although economically convenient, the downside is the antinutritional molecules often present in its active forms. Recently, a midgut gland proteolytic activity adjustment to compensate the effect of increasing concentrations of soybean trypsin inhibitor (SBTI) delivered in shrimp feed was found in Litopenaeus vannamei; which prompted us to inquire on the transcriptional response of shrimp digestive peptidases against exogenous peptidase inhibitors and connect the results for a broader comprehension of the compensatory mechanism triggered by ingestion of SBTI. Our results indicate that such response involves at least two stages: in the first hours, a drastic increase in transcription of trypsin, an inhibitor sensitive protease was observed followed by a gradual increase in transcription of putatively less-sensitive protease chymotrypsin, and a non-sensitive metalloprotease was observed. At 23 h a second doses of SBTI was administered and at 24 h, trypsin transcripts returned to basal levels, whereas the transcription of genes encoding inhibitor-insensitive peptidases increased. Taken together, this paper is the first comprehensive study of the compensatory mechanisms to exogenous protease inhibitors in Penaeidae. Specific activity and gene expression of digestive proteases observe the same pattern, indicating a phenotypic plasticity in the digestive system of L. vannamei as an adaptive response to compensate the protein digestion capacity when some of the peptidase activities are reduced by the presence of protease inhibitors.