Analysis of endoparasitoid-released proteins and their effects on host development in the system Chelonus inanitus (Braconidae)–Spodoptera littoralis (Noctuidae)
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Abstract
<p class="first" id="d21383910e65">Having shown earlier that the larva of C. inanitus
is essential in inducing the precocious
onset of metamorphosis in polydnavirus/venom containing S. littoralis, we here analysed
release of proteins by parasitoid larvae and their effects on host development. Parasitoid
larvae released proteins in vivo and in vitro in a stage dependent manner. An approximately
212 kD protein was released from the mid 1st instar onwards and additional smaller
proteins could be associated mainly with the 2nd and 3rd instar. When parasitoids
were implanted into S. littoralis larvae, parasitoid-released proteins were seen 6
hr later. When parasitoids were removed from hosts, parasitoid-released proteins persisted
in the host haemolymph for some time. Injection of antiserum against parasitoid-released
proteins after removal of the parasitoid larva accelerated the disappearance of the
212 kD protein and reduced the number of larvae entering metamorphosis precociously.
Repeated injections of concentrated parasitoid medium into polydnavirus/venom containing
larvae caused a reduction of the head capsule width and formation of miniature 6th
instar larvae; this effect was not seen in the absence of polydnavirus/venom. These
observations suggest that proteins released by the parasitoid might play a role in
modifying host metamorphosis in the presence of polydnavirus/venom, and the temporal
appearance of the 212 kD protein makes it the most interesting candidate for being
involved in such an effect.
</p>