Several types of insect cuticle contain enzymes catalyzing the formation ofof adducts between N-acetyldopamine (NADA) and N-acetylhistidine (NAH). Two such adducts, NAH-NADA-I and NAH NADA-II, have been isolated and their structures determined. In one of the adducts the link connecting the two residues occurs between the I-position (ß-position) in the NADA side chain and the 1-N atom (τ-N) in the imidazole ring of histidine. Diphenoloxidase activity alone is not sufficient for formation of this adduct, whereas extracts containing both diphenoloxidase and o-quinone-p-quinone methide isomerase activities catalyze the coupling reaction. The adduct consists of a mixture of two diastereomers and they are presumably formed by spontaneous reaction between enzymatically produced NADA-p-quinone methide and N-acetylhistidine. The other adduct has been identified as a ring addition product of N-acetylhistidine and NADA. In contrast to the former adduct it can be formed by incubation of the two substrates with mushroom tyrosinase alone. An adduct between N-acetylhistidine and the benzodioxan-type NADA-dimer is produced in vitro, when the N-acetylhistidine-NADA adduct is incubated with NADA and locust cuticle containing a 1,2-dehydro-NADA generating enzyme system. Trimeric NADA-polymerization products of the substituted benzodioxan-type have been obtained from in vivo sclerotized locust cuticle, confirming the ability of cuticle to produce NADA-oligomers. The results indicate that some insect cuticles contain enzymes promoting linkage of oxidized NADA to histidine residues. It is suggested that histidine residues in the cuticular proteins can serve as acceptors for oxidized NADA and that further addition of NADA-residues to the phenolic groups of bound NADA can occur, resulting in formation of protein-linked NADA-oligomers. The coupling reactions identified may be an important step in natural cuticular sclerotization.

<p>Insects encounter many microorganisms in nature and to survive they have developed counter measures against the invading pathogens. In <i>Drosophila melanogaster</i> research on insect immunity has mainly been focused on infections by bacteria and fungi. We have explored the immune response against natural infections of the parasite <i>Octosporea muscaedomesticae</i> and the <i>Drosophila</i> C virus as compared to natural infections of bacteria and fungi. By using Affymetrix <i>Drosophila</i> GeneChips, we were able to obtain 48 genes uniquely induced after parasitic infection. It was also clearly shown that natural infections led to different results than when injecting the pathogens. </p><p>In order to search for the ultimate role of the lepidopteran protein hemolin, we used RNA interference (RNAi). We could show that injection of double stranded RNA (dsRNA) of <i>Hemolin</i> in pupae of <i>Hyalophora cecropia</i> led to embryonic malformation and lethality and that there was a sex specific difference. We continued the RNAi investigation of hemolin in another lepidopteran species, <i>Antheraea pernyi</i>, and discovered that hemolin was induced by dsRNA<i> per se</i>. A similar induction of hemolin was seen after infection with baculovirus and we therefore performed <i>in vivo</i> experiments on baculovirus infected pupae. We could show that a low dose of ds<i>Hemolin</i> prolonged the period before the <i>A. pernyi</i> pupae showed any symptoms of infection, while a high dose led to a more rapid onset of symptoms. By performing <i>in silico</i> analysis of the hemolin sequence from <i>A. pernyi</i> in comparison with other<i> Hemolin</i> sequences, it was possible to select a number of sites that either by being strongly conserved or variable could be important targets for future studies of hemolin function.</p>

Insects encounter many microorganisms in nature and to survive they have developed counter measures against the invading pathogens. In Drosophila melanogaster research on insect immunity has mainly been focused on infections by bacteria and fungi. We have explored the immune response against natural infections of the parasite Octosporea muscaedomesticae and the Drosophila C virus as compared to natural infections of bacteria and fungi. By using Affymetrix Drosophila GeneChips, we were able to obtain 48 genes uniquely induced after parasitic infection. It was also clearly shown that natural infections led to different results than when injecting the pathogens. In order to search for the ultimate role of the lepidopteran protein hemolin, we used RNA interference (RNAi). We could show that injection of double stranded RNA (dsRNA) of Hemolin in pupae of Hyalophora cecropia led to embryonic malformation and lethality and that there was a sex specific difference. We continued the RNAi investigation of hemolin in another lepidopteran species, Antheraea pernyi, and discovered that hemolin was induced by dsRNA per se. A similar induction of hemolin was seen after infection with baculovirus and we therefore performed in vivo experiments on baculovirus infected pupae. We could show that a low dose of dsHemolin prolonged the period before the A. pernyi pupae showed any symptoms of infection, while a high dose led to a more rapid onset of symptoms. By performing in silico analysis of the hemolin sequence from A. pernyi in comparison with other Hemolin sequences, it was possible to select a number of sites that either by being strongly conserved or variable could be important targets for future studies of hemolin function.