Baculovirus infection blocks the progression of fat body degradation during metamorphosis in Bombyx mori

Abstract

The effect of baculovirus infection into silkworm pupa particularly on programmed fat body degradation during metamorphosis was investigated. Pupal fat body degradation did not occur following infection with Bombyx mori nucleopolyhedrovirus (BmNPV). There were no histolytic differences between the fat body tissues of mock and BmNPV infected papae until 48 h postinfection (p.i.). Between 48 and 72 h p.i., significant differences were observed. In order to determine whether the histolysis of fat body was due to apoptosis, genomic DNAs were purified at various p.i. times and analyzed. Rapid genomic DNA fragmentation was observed at 24 and 48 h after pupation in both mock and BmNPV infected pupae. However, BmNPV infection clearly inhibited DNA fragmentation and ladder formation at 72 h and later times p.i. Furthermore, pulse-labeling analysis showed that BmNPV infection restored protein synthesis in fat body cells. These results suggested that fat body degradation during pupal-adult development was due to apoptosis, and that BmNPV was able to evoke a cellular response in these cells.

Modes of cell death in the pupal perivisceral fat body tissue of the silkworm Bombyx mori L.

“…DNA fragmentation is a classical apoptotic characteristic feature that has been well studied in the salivary gland and mid-gut of Apis melifera larva (Gregorc and Bowen 1997;Silva de Moraes and Bowen 2000). In addition, the DNA laddering method has been adopted, since the presence of a nucleosomal ladder is an accepted characteristic for identifying the initiation of apoptosis (Tapanainen et al 1993;Tilly 1993;Iwanaga et al 2000). In the present study, we have also noted the specific time of DNA fragmentation, which occurs at 12 h of pupal day 6.…”

Programmed cell death and stem cell differentiation are responsible for midgut replacement in Heliothis virescens during prepupal instar

“…Indeed, they might represent an additional energy source during pupal-adult development after degeneration of the fat body (Larsen 1976;Iwanaga et al 2000) as this new epithelium persists throughout the pupal stage (Waku and Sumimoto 1971).…”

Identification of differentially expressed host genes in Bombyx mori nucleopolyhedrovirus infected cells by using subtractive hybridization

“…Furthermore, NPVs encode anti-apoptotic genes such as p35 or inhibitor of apoptosis (iap) to prevent premature cell death (Clem and Miller, 1993;Kamita et al, 1993;Birnbaum et al, 1994). Previously, Iwanaga et al (2000) reported that BmNPV infection blocks the progression of fat body degradation during metamorphosis in silkworms. They also reported that virus infection restores host protein synthesis that was to be repressed at a low level during pupal-adult development.…”

“…They also reported that virus infection restores host protein synthesis that was to be repressed at a low level during pupal-adult development. Degradation of fat body also has been shown to be prevented by infection with either p35 or iap1 deletion mutant, suggesting that a mechanism other than inhibition of apoptosis may be involved in this prevention (Iwanaga et al, 2000).…”