Mutations et altérations dans la transmission des informations génétiques chez la drosophile par injection d'extraits de chrysalide diapausantes ( Pieris brassicae) traitées par des ptérines

Abstract

The injection of a pterinic growth factor (folic acid) to insects in diapause under hormone-deficient conditions induced the formation of tumors. From these tumours, artificially induced in chrysalids of Pieris brassicae, a factor causing tumours was extracted which could be isolated by ultracentrifugation. The factor induced by the pterins (folic acid) is made up of light particles which contain DNA, and this DNA is the active constituent. It is a 4–8 S component after breakdown of the light particles. After injection of an extract of diapausal chrysalid treated with folic acid and a pterin mixture in Drosophila melanogaster, a reactivation of certain genes in the treated larvae-appearance of red pigment in the kynurenine cells of the alytic larval fat body inside the puparium, yellow pigment (sepiapterin) in the blood of larvae and pupae-and blockage of metamorphosis in permanent larvae and pupae were observed. Genetic modifications were evident in the surviving adults of D. melanogaster transmitted by the cytoplasm of females (there was a decrease in the number of males after the second generation). Injecting the surviving females with [ 3H]thymidine resulted in a considerable increase in DNA synthesis by the nurse cells and the migration of marked DNA from the nucleus to the cytoplasm. Administration to Drosophila larvae of an extract of diapausal chrysalids, treated with a mixture of hydrogenated pterin derivatives and various inhibitors in addition to folic acid, caused ebony mutants to appear, showing an abnormality in the melanogenic metabolism and mutants sepia and Bar in F 1 or F 2 offspring. The total absence of growth and possibly gonadotrophic hormones in Pieris chrysalids is absolutely necessary for producing mutations.