Manduca sexta

About: Manduca sexta is a research topic. Over the lifetime, 1894 publications have been published within this topic receiving 83380 citations. The topic is also known as: tobacco hornworm & goliath worm.

Techniques for Rearing Laboratory Colonies of Tobacco Hornworms and Pink Bollworms

Abstract: Larval tobacco hornworms, Manduca sexta (L.), were individually reared in polystyrene containers on an artificial diet. The developmental period (egg to adult) was completed in ca. 40 days at 26° C, which allowed production of 9 generations/year. Weights of the 5th stage larvae and pupae ranged from 7.5-9 g and 4.0-5.5 g, respectively. Survival of the immature stages ranged from 94-97%. Cage populations of 50-70 pairs of adults yielded 5000+ eggs/day when night temperatures were maintained at 26-28°C. From 1000-5000 hornworms were produced each week at an estimated cost (excluding labor and overhead) of ca. 30/1000. Colonies of the pink bollworm, Pectinophora gossypiella (Saunders), were also reared on the tobacco hornworm diet. The larvae were reared individually in polystyrene vials covered with polyethylene caps which prevented excessive drying of the larval diet even at low room humidities of 20-30%. Performance of the colony was as good as that of pink bollworms reared on other diets, and microbiol contamination was rarely encountered.

Transgenic plants protected from insect attack

Abstract: The Gram-positive bacterium Bacillus thuringiensis produces proteins which are specifically toxic to a variety of insect species. Modified genes have been derived from bt2, a toxin gene cloned from one Bacillus strain. Transgenic tobacco plants expressing these genes synthesize insecticidal proteins which protect them from feeding damage by larvae of the tobacco hornworm.

Innate immune responses of a lepidopteran insect, Manduca sexta

Abstract: Many innate immune mechanisms are conserved throughout the animal kingdom. Manduca sexta, a widely used model for insect biochemical research, employs these mechanisms to defend against invading pathogens and parasites. We have isolated from M. sexta hemolymph a group of proteins (hemolin, peptidoglycan recognition proteins, beta-1,3-glucan recognition proteins, and C-type lectins), which serve as a surveillance mechanism by binding to microbial surface molecules (e.g. peptidoglycan, lipopolysaccharide, lipoteichoic acid, and beta-1,3-glucan). The binding triggers diverse responses such as phagocytosis, nodule formation, encapsulation, melanization, and synthesis of anti-microbial peptides/proteins. Some of these responses are mediated and coordinated by serine proteinase cascades, analogous to the complement system in mammals. Our current research is focused on the proteolytic activation of prophenoloxidase (proPO)--a reaction implicated in melanotic encapsulation, wound healing, and protein cross-linking. We have isolated three proPO-activating proteinases, each of which requires serine proteinase homologs as a cofactor for generating active phenoloxidase. The proteinases and proteinase-like molecules, containing one to two clip domains at their amino-terminus, are acute-phase proteins induced upon an immune challenge. Inhibitory regulation of the proteinases by serpins and association of the proteinase homologs with a bacteria-binding lectin are important for ensuring a localized defense response. Additional serine proteinases expressed in M. sexta hemocytes and fat body have been discovered. Future research efforts will be aimed at elucidating the proteinase cascade for proPO activation and investigating the roles of proteinases in other immune responses such as processing of plasmatocyte-spreading peptide.

Expression of proteinase inhibitors I and II in transgenic tobacco plants: effects on natural defense against Manduca sexta larvae.

Abstract: Genes containing the cauliflower mosaic virus 35S promoter fused to open reading frames coding for tomato proteinase inhibitor I, tomato inhibitor II, and potato inhibitor II were expressed in transgenic tobacco plants. Inhibitor I and II proteins were identified by immunoblotting and quantified by immunoradial diffusion. Both inhibitors exhibited the molecular weights found for the native proteins in their natural environments. Extracts of leaves from transformed plants contained inhibitory activities against trypsin and chymotrypsin that reflected the levels of inhibitor I or II protein present. The results demonstrate that in tobacco leaves the introns of both inhibitor I and inhibitor II genes were excised correctly and that pre and prepro inhibitor I and II proteins were correctly processed. Growth of Manduca sexta larvae (tobacco hornworms) feeding on leaves of transgenic plants containing inhibitor II, a powerful inhibitor of both trypsin and chymotrypsin, was significantly retarded, compared to growth of larvae fed untransformed leaves. Levels of inhibitor II protein as low as 50 micrograms/g of tissue moderately affected larval growth, whereas levels above 100 micrograms/g severely reduced growth. The presence of tomato inhibitor I protein, a potent inhibitor of chymotrypsin but a weak inhibitor of trypsin, in transgenic tobacco leaves had little effect on the growth of the larvae. These experiments indicated that trypsin inhibitory activity, but not chymotrypsin inhibitory activity, was mainly responsible for the inhibition of larval growth.