EARLY TRYPSIN ACTIVITY IS PART OF THE SIGNAL-TRANSDUCTION SYSTEM THATACTIVATES TRANSCRIPTION OF THE LATE TRYPSIN GENE IN THE MIDGUT OF THEMOSQUITO, AEDES-AEGYPTI

Trypsin activity during the first hours after feeding is essential to induce late trypsin gene expression. These results are consistent with the idea that free amino acids or other products released during dige stion might be the initial signal for transcriptional activation of la te trypsin. Besides early trypsin, some other factor(s) have to be tra nslated for induction of late trypsin. This is the first case in which the proteolytic activity of a digestive enzyme is part of the signal transduction system which regulates expression of a second gene. The p resence of two trypsins allows the mosquito to assess the quality of t he meal and adjust the levels of late trypsin for a particular meal wi th remarkable flexibility.