Biomolecular changes and somatic mutations induced by UV laser irradiation at embryonic stage of Bombyx mori

Abstract

Purpose: To determine the impact of ultraviolet (UV) laser radiation on Bombyx mori embryos in terms of its effect on embryonic and larval haemolymph proteins and morphological traits.

Materials and methods: The eggs of silkworm strain NB₄D₂ were exposed to third harmonic laser pulses at 355 nm from a Nd:YAG laser for different durations of 30, 60, 90, 120, 150, or 180 sec. Morphological changes induced by the UV laser were analysed at larval, pupal and adult stages. The eggs exposed to UV laser irradiation at different developmental stages were subjected to protein analysis by sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS-PAGE). The haemolymph derived from irradiated and control larva was also analysed by SDS-PAGE.

Results: UV laser irradiation resulted in various structural polymorphisms. Asymmetrical fusion of segments was not confined to larva but persisted throughout pupal and adult stages. Development of extra caudal horn, unequal size and lack of antenna, retarded thoracic legs and variation in larval markings were observed. Comparatively, the effect of the UV laser on 8- and 16-h old embryo was greater than on the other stages. The changes in protein pattern were not distinct until the 5th day of embryogenesis as revealed by SDS-PAGE. A 178 kiloDalton (kDa) protein resolved into 198, 184 & 169 kDa polypeptides and 154 kDa new protein band along with other proteins of 110, 45, 41 & 38 kDa were noticed in irradiated eggs at the 6th day. Further, 33, 32, and 6.2 kDa new protein bands were observed in the haemolymph of 5th instar silkworm larvae derived from UV laser irradiated embryos.

Conclusions: A comparative analysis of the present study revealed that UV laser not only induced continuous structural polymorphisms (somatic mutations), but also induced protein changes with the appearance of new protein bands in embryonic and haemolymph protein. The UV laser could be a potential tool for biochemical genetics and genome analysis in B. mori.

Keywords:

• Bombyx mori
• embryo
• UV laser
• mutation
• deletion
• bimolecule & protein