Characterization of the precursor for Manduca sexta diuretic hormone Mas-DH.

We have isolated a cDNA clone encoding a precursor form of the diuretic hormone from the tobacco hornworm Manduca sexta (Mas-DH). Translation of the cDNA revealed a 138-amino acid precursor consisting of the Mas-DH amino acid sequence bounded by dibasic amino acid processing sites, a putative signal sequence, and additional peptide sequence on either side of the Mas-DH coding sequence. The region of the precursor upstream of the mature Mas-DH sequence shows limited (28%) homology to the cryptic region of the ovine corticotropin-releasing factor precursor. The Mas-DH RNA is 1.5-1.6 kilobases long; it is present in both the heads and bodies of adult and larval insects. In prewandering fifth stadium larvae, Mas-DH mRNA is expressed in brain, nerve cord, gut, and Malpighian tubules, but not in the fat body. There is a single genomic copy of the Mas-DH gene; the message is multiply spliced.