Teratocytes are dissociated cells from serosal membranes of the endoparasitoid, Microplitis croceipes, at egg hatch. These cells circulate in the hemolymph of its host, Heliothis virescens, become greatly enlarged and secrete proteins (TSP) that cause host developmental arrest, abnormalities such as incomplete metamorphosis and death similar to parasitized larvae. TSP14 is a 13.9kDa teratocyte-secreted protein that inhibits synthesis of host storage proteins linked to larval growth and development. We hypothesized that TSP14 is involved in redirecting host physiology at the post-transcriptional/translational level to support development of the endoparasitoid larvae. A cDNA encoding TSP14 has been isolated, cloned and a recombinant protein (recTSP14) expressed in the yeast, Saccharomyces cerevisiae, for functional studies. Our findings revealed the recTSP14 produced in transformed yeast is biologically active, inhibiting in vitro translation of fat body RNA of the host, H. virescens. The inhibitory activity of the recombinant protein is sensitive to standard biochemical parameters such as protein concentration, boiling, incubation time and storage conditions. Additionally, H. virescens larvae injected with recTSP14 exhibited symptoms characteristic of M. croceipes parasitism. Generally, injected host larvae showed a delay in growth and development at the CF-1 to CF-2 stage, and developed larval-pupal intermediates, which eventually succumbed to host death. While recTSP14 alters insect host physiology in vivo, addition of recTSP14 to cultures of selected mammalian cells did not inhibit the incorporation of [35S]-labeled methionine into proteins in vitro - an important safety consideration of transgenic plants to humans and other non-target organisms.
Species 1: Hymenoptera Braconidae Microplitis croceipes
Species 2: Lepidoptera Noctuidae Heliothis virescens (tobacco budworm)
Keywords: biological control, inhibition of translation
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