Cell death in the salivary glands of metamorphosing calliphora vomitoria

Abstract

The salivary gland cells of Calliphora vomitoria larvae initiate and complete their own destruction in a programmed manner at the onset of metamorphosis. On entering the post-feeding period the larvae come to rest and the polytene salivary gland cells show a significant increase in DNA synthesis followed closely by a surge of mRNA synthesis accompanied by increasing protein production. During this prelude to cell death the new mRNA gives rise to at least 10 new proteins. The first new proteins having a MWt between 30 and 100kD appear by day 8 of the life-cycle and a number persist until the advent of cell death on day 9. Other new proteins appear in a cascade of production during day 8 and in vitro translation of mRNA produced at this time shows a new 55kD protein appearing before cell destruction. Significantly no evidence of DNA degeneration or laddering associated with classical apoptosis was observed, on the contrary considerable DNA synthesis in the form of chromosomal endoduplication or "genomic amplification" was seen; selective gene expression being apparently controlled at translational level. Overall the results strongly suggest a synthetically mediated programmed cell death in the metamorphosing salivary glands of the blow-fly which is distinct from apoptosis.

Programmed cell death during metamorphosis in the blow-flyCalliphora vomitoria

“…Supporting biochemical evidence on the lack of endonuclease activation has previously been reported (Bowen 1993a;Bowen et al, 1993). Zakeri et al (1993) have added to the claim that programmed cell death is not always initially accompanied by endonuclease activation.…”

Rearrangement of the tubulin and actin cytoskeleton during programmed cell death in Drosophila salivary glands

“…Extensive fragmentation of nuclei occurs only at very late in PCD, 13 h after P1. It has been suggested previously (Zakeri et al, 1993Bowen et al, 1993) that at least some insect tissues do not undergo early DNA fragmentation during PCD. Proteases and nucleases are responsible for apoptotic DNA fragmentation (Weaver et al, 1994;.…”

Programmed cell death in salivary glands of Drosophila arizonae and Drosophila mulleri

“…Bowen et al (1993), in their studies with Calliphora vomitoria, did not find classic apoptotic traits such as cell shrinkage and chromatin compaction. Lockshin and Zakeri (1990) argued for a separate category of cell death that occurs in insect development, developmental PCD, which specifically does not demonstrate endonuclease activation.…”

“…Jiang et al (1997) have shown that in Drosophila melanogaster salivary gland histolysis is triggered by steroid hormones. Many researchers have described apparently nonapoptotic or aberrant apoptotic modes of PCD during insect development (Schwartz, 1991) and metamorphosis (Lockshin and Zakeri, 1990;Bowen et al, 1993;Silva de Moraes and Bowen, 2000). According to Bowen et al (1993), who studied cell death in the salivary glands of Calliphora vomitoria during development, the classical apoptotic marker (DNA fragmentation and degeneration) does not apply to this model.…”

“…Many researchers have described apparently nonapoptotic or aberrant apoptotic modes of PCD during insect development (Schwartz, 1991) and metamorphosis (Lockshin and Zakeri, 1990;Bowen et al, 1993;Silva de Moraes and Bowen, 2000). According to Bowen et al (1993), who studied cell death in the salivary glands of Calliphora vomitoria during development, the classical apoptotic marker (DNA fragmentation and degeneration) does not apply to this model. Nevertheless, Gregorc and Bowen (1997) and Silva de Moraes and Bowen (2000), studying respectively salivary glands and midgut of the Apis mellifera larva, observed DNA fragmentation frequently associated with cell death.…”