| The cotton bollworm, Helicoverpa armigera (Hubner) (Lepidoptera:Noctuidae) is one of the most serious insect pest in the world. The moths of this nocturnal insect display a conspicuous positive phototactic behaviour to light stimuli, and are especially sensitive to Ultraviolet (UV) light. In the present study, we study the effects of UV light irradiation on adult longevity and reproduction, molecular cloning and characterization of hsp90 and hsp70 and their expression patterns during thermal stress and UV light irradiation in H. armigera. Main results were summarized as follows:1. Oxidative damage analysis in H. armigera adults after exposure to UV lightThe effects of UV light irradiation on malondialdehyde (MDA) and protein carbonyl contents were investigated in H. armigera adults. The adults were exposed to UV light for various time periods (0,30,60 and 90 min). We found that exposure to UV light for 30, 60 and 90 min resulted in increased protein carbonyl content. However, there was no significant difference in MDA content in H. armigera adults following UV light exposure. We have confirmed that UV light may disturb the functional activity of protein and intensify the activity of protein oxidation process. This indicates that UV light is threatening to H. armigera adults.2. Effects of UV light irradiation on longevity and reproduction of H. armigera, and development of its F1 generationThe effects of UV light irradiation on adult longevity and reproduction of H. armigera were investigated, as well as the development of the F1 generation. Paired adults were exposed to UV light for various time periods (0,1,5 and 9 h/day), until the end of adult life. The results showed that adult longevity decreased with increasing exposure time for both sexes, and a significant decrease was observed after exposure for 5 and 9 h/day. Fecundity increased when adults were exposed for 1 and 5 h/day, and a significant difference was observed in the 5 h/day group. Oviposition rate of females in all treatments were significantly higher than control. Exposure to UV light for longer periods (5 and 9 h/day) caused a decline in cumulative survival of F1 immature stages, but no significant differences were found in egg hatching, pupation and eclosion. The developmental periods of F1 larvae were significantly prolonged after exposure to UV light for 5 and 9 h/day. UV light irradiation had no significant effects on F1 pupae period. All these physiological effects under UV irradiation may be strategies for insect adaptations.3. Effects of UV light irradiation on juvenile hormone titres of H. armigeraThe effect of UV light irradiation and age on juvenile hormone titres from H. armigera were measured with HPLC. The results indicated that JHI, JHII and JHIII titres varied signficantly across age and UV light irradiation. Female H. armigera showed the expected response to age and temperaturs and UV light irradiation. JHI, JHII and JHIII titres in the 5 and 9 h/day group decreased significantly. JHI, JHII and JHIII titres are lowest in the 9 h/day group. This indicates that UV light is threatening to H. armigera adults.4. The expresson patterns of hsp90 and hsp70 during thermal stress and UV light irradiation in H. armigeraThree heat shock protein transcripts, hsp90, hsp70, hsc70, isolated from H. armigera, were evaluated for their responsiveness to thermal stress and UV light irradiation. The expression patterns after heat shock indicated that hsp90 and hsp70 were up-regulated, and hsc70 was indeed a constitutively expressed member of hsp70 family. The expression patterns after UV light irradiation indicated that hsp90 was also up-regulated. Our results also indicated that hsps are responsive to thermal stress and UV light irradiation in H. armigera.5. Molecular cloning and characterization of hsp90 and hsp70 cognate cDNAs in H. armigeraThe sequence data of hsp90 and hsp70 indicates a 2476-bp full-length hsp90 cDNA with a 2154-bp ORF starting at nucleotide 163 and terminating at nucleotide 2316, which encodes 717 amino acid residues with a putative molecular mass of 82.51 kDa and a calculated pI of 4.92, a 2246-bp full-length hsp70 cDNA with a 1905-bp ORF starting at nucleotide 159 and stopping at 2063, which encodes 634 amino acid residues with a putative molecular mass of 69.98 kDa and a calculated pI of 5.70. Multiple sequence alignments indicate that the deduced amino acid sequences of H. armigera Hsp90 and Hsp70 show very high homology to their corresponding sequences in other species.Two phylogenetic analysis of Hsp90 and Hsp70 sequences were consistent with well known classification of insects.
|
PDF Full Text Request