NEUROPEPTIDE REGULATORS OF THE JUVENILE HORMONE BIOSYNTHESIS (IN VITRO) IN THE BEETLE, Tenebrio molitor (COLEOPTERA, TENEBRIONIDAE)

The genome of Tribolium castaneum encodes two allatostatin [ AS type B; W(X)(6)Wamide and AS type C; PISCF-OH] and one allatotropin (AT) precursor, but no AS type A (FGLamide) (Tribolium Genome Sequencing Consortium, 2008: Nature 452: 949-955). Here we studied the activity (in vitro) of peptides derived from these precursors on the synthesis/release of juvenile hormone (JH) III. The corpora cardiaca-corpora allata (CCCA) complexes of adult females of another tenebrionid beetle, the mealworm Tenebrio molitor, were used. Incubating the gland complexes in a medium containing Trica-AS B3 peptide, we showed that the peptide has allatostatic function in T. molitor. The activity of the type C AS depended on the age of the test animals and their intrinsic rate of JH III biosynthesis. The Trica-AS C peptide inhibited the JH release from CA of 3-day-old females with a high intrinsic rate of JH synthesis, but activated JH release from the CA of 7-day-old females with a lower intrinsic rate of JH production. The allatotropin peptide (Trica-AT) also activated the JH release from the CA of 7-day-old females in a dose- dependent and reversible manner. Unexpectedly, a type A AS derived from the precursor of the American cockroach Periplaneta americana (Peram-ASA2b) inhibited the JH release from the CA of younger and older females in the concentration range of 10(-8) to 10(-4) M, and the effects were fully reversible in the absence of peptide. These data suggest a complex role of