Global expression profile of silkworm genes from larval to pupal stages: Toward a comprehensive understanding of sexual differences

Abstract Sexual dimorphism is a widespread phenomenon in many higher animals. The genes and gene networks that underlie sex differences are poorly understood. Using microarray data we analyzed sex-related differences in the global expression profiles of silkworm genes from larval to pupal stages. Sex-biased genes could be divided into three clusters. Cluster 1 contained 932 genes that showed a female-biased expression trend at first and a male-biased trend afterward. Cluster 2 included 283 male-biased genes. Cluster 3 was comprised of 497 female-biased genes that were expressed during the late pupal stage. Cluster 1 genes were found to be related closely to cuticle proteins, hormones, binding proteins, enzyme regulators, structural proteins, transcription regulators and so on. Several genes in clusters 2 and 3 were associated with spermatogenesis and oogenesis, respectively. The chromosomal distribution of sex-biased genes showed evidence of chromosomal enrichment. In particular a large number of the silkworms’ male-biased genes are located on the Z chromosome. These results provide new insights into the molecular differences that dictate sexual dimorphism in the silkworm.