Ecdysteroid-inducible genes in the programmed cell death during insect metamorphosis

The anterior silk gland of the silkworm, Bombyx mori, undergoes programmed cell death (PCD) during pupal metamorphosis and PCD is triggered by 20-hydr oxyecdysone (20E) in vitro. In order to identify the genes responsible for the PCD, we subtracted cDNAs prepared from the anterior silk glands incubat ed in the presence or absence of 20E in vitro. After a series of screenings by dot blot hybridization, DNA sequencing and reverse transcription polyme rase chain reaction (RT-PCR), we obtained seven novel genes that were activ ated by 20E in vitro. Nucleotide sequence analysis indicated that two cDNAs (EN78 and EC08) did not have any obvious region to encode proteins, while five genes, designated EC74, EN86, EN03, EN10 and EN16, encoded proteins th at are similar to inorganic phosphate cotransporter, TIA-1-like protein, ch itinase-related protein, translation-initiation-factor subunit and annexin, respectively. Expression profiles of the genes after 20E stimulation indic ated that four genes could be classified as early genes, while two are dela yed early genes. The genes identified may provide insight into the PCD indu ced by a steroid hormone. (C) 2001 Elsevier Science Ltd. All rights reserve d.