Abstract

Bombyxin (BBX) of the silkworm, Bombyx mori, is an insulin-like peptide (ILP). To further study the function of the BBX-B8 gene, the effects of inhibiting the expression of BBX-B8 gene on organ development, reproduction and trehalose metabolization of the silkworm were investigated. 48 h after the injection of BBX-B8 dsRNA into the 3-day larvae of fifth-instar (10 μg per larvae; 10 μl; the average weight: 3 g/larvae), the mRNA level of BBX-B8 in the brain of silkworm was declined strikingly by 37.33%; 72 h after injection, the mRNA level of BBX-B8 was decreased by 30%. After the injection of BBX-B8 dsRNA into the 3-day larvae of fifth-instar (1 or 5 μg per larvae; 10 μl), development of pupal wing imaginal discs was suppressed, more deformed adult wings were found. The number of mature eggs in the oviduct respectively increased by 7.86 and 12.62% when pupa were injected with BBX-B8 dsRNA (10 or 15 μg per larvae; 10 μl) on the first day of pupation. 72 h after the injection of BBX-B8 dsRNA (10 μg per larvae; 10 μl) into the 3-day larvae of fifth-instar, the trehalose level of hemolymph was elevated by 12.68% in silkworm. These results suggest that BBX-B8 plays an important role in organ development, reproduction and the metabolization of trehalose of silkworm.

Key words: Silkworm, insulin-like, RNAi, organ growth, reproduction.