Insect immunity. Isolation of cDNA clones corresponding to attacins and immune protein P4 from Hyalophora cecropia.

Diapausing pupae of the Cecropia moth (Hyalophora cecropia) respond to an injection of live bacteria by the selective synthesis of certain types of RNA and immune proteins (designated P1-P9). The in vitro translation products of RNA from both injured and infected pupae showed specific patterns with a defined number of extra bands. Some proteins characteristic of the normal RNA were reduced in the immune RNA translation products. Antibody reaction was used to show the selective synthesis of immune proteins P4 and P5 with mRNA from pupae subjected to injury or infection. The protein synthesized in vitro, which cross-reacted with P5 antibodies, is most likely a precursor of the attacins described in the preceding paper. A cDNA clone bank was prepared and two clones were isolated and shown to contain 750 bp corresponding to P4 and 250 bp of attacin information. These clones were used to estimate the sizes of the mRNAs by Northern blotting and to estimate, by RNA/DNA hybridization, the levels of P4 and P5 mRNA. In vivo incorporation of [35S]methionine into attacins and P4 during different conditions was compared with the levels of the corresponding mRNA.