Isolation of the gene for the precursor of Phe-Gly-Leu-amide allatostatins in the termite Reticulitermes flavipes

Allatostatins (ASTs), with a C-terminal sequence Tyr/Phe-Xaa-Phe-Gly-Leu/Ile-amide, are multifunctional neuropeptides that were first discovered by their ability to inhibit juvenile hormone (JH) synthesis by the corpora allata (CA) in cockroaches. These A-type ASTs have since been demonstrated to inhibit JH synthesis in crickets, termites and more recently locusts. The gene for the precursor of A-type ASTs has been identified in several species of cockroaches, in crickets and in locusts, but not yet in termites, although 5 AST peptides were isolated from the lower termite Reticulitermes flavipes that are identical to known cockroach ASTs. In this study, primers designed from AST amino acid sequences of cockroaches are used to identify the gene for the preproAST peptides in R. flavipes. In addition, the expression of the gene in brain tissues is demonstrated for egg-laying and non-egg-laying neotenic reproductives. The gene codes for 14 individual peptides and its sequence is closer to that of cockroaches and the cricket than to that of other insect orders in which these peptides do not act as allatostatins. Among the known cockroach AST genes, the termite AST gene is most similar to that of Periplaneta americana, a species belonging to the primitive family Blattidae.