Differential expression of muscle and cytoplasmic actin genes during development of Bombyx mori

Transcripts of three actin genes accumulate differentially during development of Bombyx mori, indicating distinct patterns of expression for each gene. Two of them are muscle actin encoding genes since one is expressed only in adult muscles which are formed during the late pupal period and the other one is expressed in all the larval as well as adult muscles tested. The third one codes for a cytoplasmic actin present particularly in embryos, larval silk glands and pupae. The structure of the 3′ end of each gene has been determined and indicates the presence of regulation in the choice of polyadenylation sites for the larval and adult muscle actin gene at different developmental stages. The pattern of accumulation of the Bombyx actin transcripts during development has been compared to that of Drosophila actin genes and indicates that three classes of actin genes can be distinguished in these two insect species: adult muscle actin genes, larval and adult muscle actin genes and cytoplasmic actin genes.