Localization, expression, and secretion pathway of diapause hormone in embryo and larva of the silkworm, Bombyx mori

In this paper, the distribution and expression of diapause hormone (DH) at mRNA and protein levels in the central nervous system of Bombyx mori embryo and larva were studied using whole-mount in situ hybridization and immunocytochemistry. Whole-mount immunocytochemistry revealed that the distribution of the DH-like immunoreactivity was throughout the central nervous system including the brain, suboesophageal ganglion (SG) and thoracic ganglia (TG); and that the corpus cardiacum and terminal abdominal ganglion may be the site for DH release due to the presence of strong immunoreactivity. In situ hybridization with the probe labeled by digoxigenin shows that the Bom-DH mRNA was also localized in the mandibular, maxillary, labial cell clusters. In addition, a pair of lateral neurons in the SG and a pair of ventral midline neurons in each TG expressing the Bom-DH transcript were also identified. These results were consistent with the localization of Bom-DH mRNA in larva by in situ hybridization and the distribution of the gene by RT-PCR, which is some different from the results reported previously.