Insect Biochemistry and Molecular Biology 30 2000 719–727 www.elsevier.comlocateibmb
Interaction between Manduca sexta allatotropin and Manduca sexta allatostatin in the fall armyworm Spodoptera frugiperda
Uwe Oeh
a
, Matthias W. Lorenz
a
, Hubert Dyker
b
, Peter Lo¨sel
b
, Klaus H. Hoffmann
a,
a
Lehrstuhl Tiero¨kologie I, Universita¨t Bayreuth, D-95440 Bayreuth, Germany
b
Bayer AG, Central Research, D-51368 Leverkusen, Germany Received 31 October 1999; received in revised form 31 December 1999; accepted 25 January 2000
Abstract
A peptide that strongly stimulates juvenile hormone JH biosynthesis in vitro by the corpora allata CA was purified from methanolic brain extracts of adult Spodoptera frugiperda. Using HPLC separation followed by Edman degradation and mass spec-
trometry, the peptide was identified as Manduca sexta allatotropin Mas-AT. Treating the CA from adult S. frugiperda with synthetic Mas-AT at 10
26
M caused an up to sevenfold increase in JH biosynthesis. The stimulation of JH synthesis was dose-dependent and reversible. Synthetic M. sexta allatostatin Mas-AS 10
26
M did not affect the spontaneous rate of JH secretion from CA of adult S. frugiperda, nor did any of the allatostatins of the Phe–Gly–Leu–amide peptide family tested. However, when CA had been
activated by Mas-AT 10
26
M, addition of synthetic Mas-AS 10
26
M reduced JH synthesis by about 70. This allatostatic effect of Mas-AS on allatotropin-activated glands was also reversible. When CA were incubated in the presence of both Mas-AT 10
26
M and various concentrations of Mas-AS from 10
28
to 10
25
M, the stimulation of JH-biosynthesis observed was inhibited in a dose-dependent manner. The experiments demonstrate a novel mechanism of allatostatin action. In S. frugiperda JH synthesis
was inhibited only in those glands which had previously been activated by an allatotropin.
2000 Elsevier Science Ltd. All rights reserved.
Keywords: Noctuidae; Fall armyworm; Spodoptera frugiperda; Juvenile hormone; Corpora allata; Allatotropin; Allatostatin
1. Introduction
The pioneering investigations of Kopec 1917 were the first to infer that metamorphosis in insects is hor-
monally regulated. Kopec’s experiments induced a flood of investigations on the hormonal regulation of various
processes in insects. Basically, the development and metamorphosis of insects depend on precise regulation
of the levels of ecdysteroids and juvenile hormones for reviews see Nijhout, 1994; Hardie, 1995; Ga¨de et al.,
1997. The juvenile hormones JH are unique hor- mones, sesquiterpenoids, which are important in almost
every aspect of insect development and reproduction Riddiford, 1994; Wyatt and Davey, 1996. These
include embryogenesis, larval moulting, metamorphosis, vitellogenin synthesis and ovarian development, poly-
Corresponding author. Tel.: +
49-921-552650; fax: +
49-921- 552784.
E-mail address:
klaus.hoffmannuni-bayreuth.de K.H.
Hoffmann.
0965-174800 - see front matter
2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 5 - 1 7 4 8 0 0 0 0 0 4 3 - 6
morphism, diapause regulation, and various aspects of metabolism associated with these functions. Juvenile
hormones are synthesized and released from the corpora allata CA, a pair of endocrine glands in the posterior
region of the head, closely associated with the stomato- gastric nervous system Tobe and Stay, 1985. Various
JH homologues were found in different insect species Schooley et al., 1984. JH III C
16
-JH is the prevalent insect JH; the higher homologues JH 0, I, II are only
found in Lepidoptera Schooley et al., 1984. A new type of JH was identified in higher dipterans, the JH III bise-
poxide JHB
3
Richard et al., 1989. In many lepidop- teran species, JH I, II, and III were found consistently
in adult females, with different ones predominating in various species Schooley et al., 1984. Moth CA seem
to exhibit a biochemical sexual dimorphism in that JH acid homologues are released by CA of male moths
Bhaskaran et al., 1988; Cusson et al., 1993. Our recent studies demonstrated that CA of the fall armyworm, Spo-
doptera frugiperda, synthesize and release mainly JH III diol, and a lesser amount of JH II diol, when incubated in
720 U. Oeh et al. Insect Biochemistry and Molecular Biology 30 2000 719–727
vitro in the presence of radiolabelled methionine Range, unpublished data.
Levels of JH in haemolymph or tissues are affected by the rate at which the hormones are biosynthesized
by the CA and the rate at which these molecules are metabolized
or excreted.
Although JH-degrading
enzymes are known to play a role in determining physio- logical levels of JH, it is likely that the overall control
of the JH level is more intimately linked to changes in the rates of its synthesis Tobe and Stay, 1985; Weaver
et al., 1998. During the last decade, interest has focused on signals or factors that regulate JH biosynthesis by the
CA. Depending on the species and developmental stage, the regulatory signals may reach the glands via the hae-
molymph or via nervous connections. These signals may be
either stimulatory
allatotropic or
inhibitory allatostatic in nature Tobe and Stay, 1985; Goodman,
1990; Stay et al., 1994. So far, a large number of neuro- peptides that are potentially inhibitory on JH production
by the CA in vitro have been isolated from the brains of several insect species moths, cockroaches, locusts,
crickets, flies and bees; for reviews see Bendena et al., 1997; Ga¨de et al., 1997; Weaver et al., 1998; Hoffmann
et al., 1999. These allatostatins can be divided into three groups. One peptide family is characterized by a com-
mon C-terminal pentapeptide sequence YFXFGLI- amide allatostatin A family; allatostatin superfamily. In
some species these peptides have no effect on the CA of the source insect, but instead exhibit myo-inhibiting
properties Duve and Thorpe, 1994. The second group consists of peptides which were isolated from Gryllus
bimaculatus and which have a common amino acid Trp at positions 2 and 9 allatostatin B family; W
2
W
9
-peptide family Lorenz et al., 1995a. Manduca sexta allatosta-
tin Mas-AS is the only known representative of the third “allatostatin family”. Mas-AS shows no sequence
similarity to any other allatostatin Kramer et al., 1991 and is the only allatostatic neuropeptide isolated from a
lepidopteran species. It was first isolated from M. sexta Kramer et al., 1991, but in Pseudaletia unipuncta a
cDNA could be characterized that also encodes the 15- residue peptide Jansons et al., 1996. Audsley et al.
1998 identified an apparently identical peptide to Mas- AS in Lacanobia oleracea. Mas-AS strongly inhibits JH
biosynthesis in vitro by CA of fifth instar larvae and adult females of M. sexta. It also inhibits the CA of the
moth, Heliothis virescens, but had no effect on CA of two orthopteroid species, Periplaneta americana and
Melanoplus sanguinipes, or on CA of the beetle Teneb- rio molitor Kramer et al., 1991.
To date, only one allatotropin has been identified Kataoka et al., 1989. This allatotropin was isolated
from 10,000 heads of pharate adults of M. sexta and was called
M. sexta
allatotropin Mas-AT;
GFKNVEMMTARGF–NH
2
. Mas-AT stimulates JH biosynthesis in vitro in CA of adults of M. sexta and H.
virescens Kataoka et al., 1989, and also of the moth L. oleracea Audsley et al., 1999. No CA-activating
effect by Mas-AT was found in any non-lepidopteran species Hoffmann et al., 1999.
These results indicate an exceptional position of the lepidopteran order with respect to the regulation of CA
activity. In the fall armyworm, S. frugiperda, little is known about allatoregulating peptides or the control of
JH biosynthesis in general. In this paper, we report on the identification of a peptide which strongly stimulates
JH biosynthesis in vitro by the CA of adult females, and we demonstrate a novel mechanism of allatoregulation,
whereby JH biosynthesis is inhibited by Mas-AS only in those glands which had previously been activated by
the M. sexta allatotropin.
2. Materials and methods
