Programmed cell death in intestinal cells of Bombyx mori during metamorphosis: Morphological observation of autophagy and apoptosis and expression of the ecdysone-regulated genes

During metamorphosis in insect, degeneration and dissolution of the larval tissues, which is triggered by ecdysone hormone (EH), require programmed cell death, such as autophagy and apoptosis. Morphological observation on autophagy and apoptosis and analysis of ecdysone-regulated gene expression in the epithelium cells of Bombyx mori gut indicated that the Cvt, autophagy, mitophagy and reticulophagy pathways of autophagy occurred in intestinal epithelium cells during the larval to pupal metamorphosis. The typical DNA ladder of apoptosis was also detected in the degenerating epithelium cells. The expression peaks of transcripts of the EH receptor gene BmEcR and earlier transcriptional genes BmHR39、BmE74A appeared before pupation, but BmFTZ-F 1 expressed later. All the data together suggested that the early expression of BmEcR、BmHR39、BmE74A might initiate autophagy and apoptosis, and autophagy pathway occurred dominantly and earlier than apoptosis pathway. This work was supported by the “863 project” (2006AA10A119), the “973 Project) (2005CB121000), NNSF (30370716, 30570938) of China.