Studies on embryonic diapause in the pnd mutant of the silkworm, Bombyx mori: Genetic control of embryogenesis

Abstract

The pigmented and non-diapausing egg mutant ( pnd) of the silkworm, Bombyx mori, has a defect as a result of which embryos never enter into diapause, even though the eggs have been exposed to the diapause factor. In the mutant homozygous embryos, two distinct peaks of DNA synthesis which correspond to the stages of cellular blastoderm and organogenesis were detected until blastokinesis. On the other hand, in the heterozygous embryos derived from moths of homozygous pnd females, a paternal pnd + gene caused the embryos never to develop beyond late gastrulation, at which stage the embryos enter into diapause; the heterozygous embryos exhibit only one peak of DNA synthesis corresponding to the cellular blastoderm stage. We conclude that the paternal pnd + gene might participate in the process of suppressing DNA synthesis at the early-middle gastrula stage.