PBAN activates pheromone biosynthesis in lepidopteran
sex pheromone glands. MRCH is structurally identical to
PBAN. PBAN is a member of the FXPRLamide peptide
family and is processed from a precursor peptide encoded
by the DH-PBAN gene.
PBAN was first discovered as a peptide hormone that
is produced by the brain-subesophageal ganglion (Br-SG)
complex. It activates the biosynthesis of the sex pheromone
in the pheromone glands of the corn earworm,
Heliothis/Helicoverpa zea.1 This hormone was isolated from
the H. zea Br-SG complexes. Two variants have been isolated
in the silkworm Bombyx mori.MRCH was first
discovered as the hormone controlling the melanization
of the larval cuticle of the armyworm Mythimna separate
(Leucania, Pseudaletia) isolated from the head extract of
B. mori.
Regulation of synthesis and release
In B. mori, two paired mandibular neuromere (SMx)
cells and three paired maxillary neuromere (SMd) cells
of the SG are involved in PBAN secretion. The regulation
of synthesis and the route of secretion are the same as for
DH.
In B. mori, PBANR mRNA is detected mainly in the
pheromone glands (PGs) immediately after adult emergence
and in the developing ovaries. Lower levels of
mRNA are detected in the midgut and the brain of
6-day-old fifth instar larvae.
The target of PBAN in adult female moths is the PG
cells, which are found as intersegmental tissues located
between the eighth and ninth abdominal segments in
heliothines and B. mori.Injection or administration
of PBAN into intact female moths, isolated abdomens,
or in vitro cultured PG stimulates pheromone production
by the PG.In Helicoverpa armigera, PBAN is known to
regulate the production of the hairpencil pheromone in males.When the larvae of some kinds of armyworms
grow under crowded conditions, their cuticle is heavily
melanized. MRCH is responsible for melanin synthesis
in this process, but the mode of action of this hormone
is not yet fully understood.
