ИСТИНА

The stored product pests Tenebrio molitor and Tribolium castaneum are model beetles from the family Tenebrionidae. We identified, annotated and compared predicted sets of serine peptidases from the S1A chymotrypsin family (SP) in the gut transcriptomes of T. molitor and T. castaneum larvae and evaluated relative expression levels of their mRNA. In T. molitor larvae we found 183 sequences similar to SP, but only 87 represented active peptidases. The residual 96 sequences had substitutions in the catalytic triad and were classified as inactive homologs of serine peptidases (SPH). 31 sequences of active SP were related to trypsins, two to chymotrypsins A/B, one to chymotrypsin C, 13 were chymotrypsin-like peptidases, 12 pancreatic elastases I, and the specificity of 28 peptidases was uncertain due to unusual residues in the substrate binding site. T. castaneum contained 178 SP sequences, of which 98 represented active peptidases, and 80 SPH. T. castaneum contained many more trypsin sequences – 51, and fewer chymotrypsin sequences than T. molitor: one chymotrypsin A/B, one chymotrypsin C, and only five chymotrypsin-like peptidases. Three sequences were annotated as pancreatic elastases I and 37 peptidases were with uncertain specificity. These data are reflective of a highly complex digestive organization in these larvae, presumably a result of high selection pressure of cereal inhibitors. Analysis of the relative expression levels of SP mRNA revealed that each group of SP usually contained one major SP with the expression level exceeding 50% of the total expression of the whole group, a number of peptidases with medium level of expression, and many SP with minor level of mRNA expression. Usually the major SP from each group of T. molitor and T. castaneum SP were not orthologous. Some SPH had rather high levels of mRNA expression, and this implies that they have important physiological functions. This work was supported by RFBR grants 17-54-61008 Egypt_a, 18-04-01221_a.