Effects of endogenous esterases and an allatostatin on the products of Manduca sexta larval corpora allata in vitro

Abstract

A rapid and simple method has been developed for the simultaneous measurement of juvenile hormone (JH) and JH acid synthesized in vitro by larval corpora allata (CA) of the tobacco hornworm, Munducu sextu. An organic solvent partition of incubation medium efficiently separates JH acid from JH, and a radioimmunoassay which recognizes the two moieties equivalently is then employed to quantify each. The change in the biosynthetic product of the CA from JH to JH acid appears to begin slowly at the time of ecdysis to the last (fifth) larval stadium and is not complete until just prior to wandering (day 4). The inclusion of the JH esterase inhibitor S-benzoyl-0-ethyl phosphoramidothiolate in incubations of corpora allata revealed that the activity of JH esterases from the gland parallels gland activity and that significant hydrolysis of newly synthesized JH by these esterases occurs in incubations of glands taken at the beginnings of the fourth and fifth larval stadia. An allatostatin, which is proposed to inhibit the corpus allatum during.the time of the change in its product, inhibits both JH I and JH I acid synthesis.

Control of juvenile hormone biosynthesis in Bombyx mori: Cloning of the enzymes in the mevalonate pathway and assessment of their developmental expression in the corpora allata

“…Instead, the CA probably synthesize JH acid during the prepupal stage ( Fig. 6), as observed in Manduca sexta (Bhaskaran et al, 1986;Janzen et al, 1991); in this species, JH acid is converted to JH by JHAMT in imaginal discs (Sparagana et al, 1985). The increase in both JH and JH acid titers observed from day 6 (SP) to pupation in Bombyx (Plantevin et al, 1987;Niimi and Sakurai, 1997), seems to be due to the conversion of JH acid to JH by JHAMT in peripheral tissues, such as ovaries and testes, where low but significant levels of JHAMT expression were observed (Shinoda and Itoyama, 2003).…”

Regulation of JH titers: The relevance of degradative enzymes and binding proteins

“…Sparagana et al (1984) first demonstrated that CA from wandering stage larvae and prepupae of Manduca sexta secrete only JH acid. Production of JH acid begins early in the last stadium, and JH acid is the sole product of the CA after day 4, the time of commitment (Bhaskaran et al, 1986;Janzen et al, 1991). It has been proposed that after commitment, hemolymph JH titers result from the conversion of JH acid to JH by the enzyme JH acid methyl transferase.…”

Juvenile hormone acid methyltransferase: A key regulatory enzyme for insect metamorphosis

“…During the last instar JH disappears from the hemolymph, and a surge of small ecdysteroid titer at the end of the feeding stage induces early metamorphic responses, such as wandering behavior and the pupal commitment of the epidermis (1). Toward the end of the feeding period, the CA of M. sexta stops secreting JH and henceforth secretes only JH acid (JHA) thereafter (10)(11)(12). This physiological switching observed in the CA during metamorphosis is considered to be caused by the loss of JHA methyltransferase (JHAMT) activity in the tissue (13).…”