Expression of the gonad-specific small heat shock protein, CfHSP20.2, in the spruce budworm, Choristoneura fumiferana (Clem.).

Small heat shock proteins (sHSPs) play important roles in insect development and stress resistance. However, the in vivo functions and mechanisms of action remain largely unknown or unclear for most members of the sHSPs in insects. This study investigated the expression of CfHSP20.2 in the spruce budworm, Choristoneura fumiferana (Clem.) under normal and heat-stress conditions. Under normal conditions, CfHSP20.2 transcript and protein were highly and constantly expressed in the testes of male larvae, pupae and young adults and in the ovaries of female late-stage pupae and adults. After adult eclosion, CfHSP20.2 remained highly and almost constantly expressed in the ovaries, but in contrast, was downregulated in the testes. Upon heat stress, CfHSP20.2 was upregulated in the gonads and non-gonadal tissues in both sexes. These results indicate that CfHSP20.2 expression is gonad-specific and heat-inducible. This provides evidence that the CfHSP20.2 protein plays important roles during reproductive development under normal environmental conditions, while under heat-stress conditions, it may also enhance the thermal tolerance of the gonads and non-gonadal tissues.

Molecular characterization of eight ATP-dependent heat shock protein transcripts and their expression profiles in response to stresses in the spruce budworm, Choristoneura fumiferana (L.).

Heat shock proteins (HSPs) greatly contribute to insect stress tolerance and enhance survival and adaptation in severe environmental conditions. To investigate the potential roles of HSPs in the spruce budworm, Choristoneura fumiferana (L.), an important native pest of forests in North America, we found eight ATP-dependent HSP transcripts (CfHSPs). Based on molecular characteristics, the identified HSP genes were classified into HSP70 and HSP90 families, and phylogenetic results showed that they had orthologues in other insects. The transcript levels of these HSPs were measured using RT-qPCR under normal and stressful conditions in the laboratory. Under normal conditions, three HSP genes were consistently expressed in all life stages, whereas expression of the other five genes was dependent on the developmental stage. In the larvae, most CfHSP transcripts displayed similar expression levels among different tissues. Under heat shock conditions, one HSP70 gene and one HSP90 gene were upregulated in all life stages. One HSP70 gene was upregulated after cold injury in the larval stage. With starvation, HSP gene expression exhibited complex expression patterns; most of them were downregulated. These results suggest that the ATP-dependent HSPs have multiple roles during normal development as well as under stressful conditions including heat, cold injury and starvation.

Expression profiles of 14 small heat shock protein (sHSP) transcripts during larval diapause and under thermal stress in the spruce budworm, Choristoneura fumiferana (L.).

Diapause is an important strategy for certain insect species to survive unfavorable environmental conditions, including low temperatures experienced when they overwinter in cold climate. Many studies have indicated that the increased expression of heat shock proteins during diapause improves the thermal tolerance of insects. However, the relationship between small heat shock proteins (sHSPs) and diapause is not clear or well-researched. In this study, we investigated the transcript levels of 14 sHSP genes in the spruce budworm, Choristoneura fumiferana, a major pest of spruce and fir in Canada, during pre-diapause, diapause, and post-diapause under normal rearing conditions and in response to a heat shock treatment. We found that sHSP expression profiles could be classified into five patterns under normal laboratory conditions: pattern I was upregulated only during pre-diapause, pattern II was upregulated only during diapause, pattern III was constantly expressed throughout diapause, pattern IV was upregulated in both pre-diapause and diapause, and pattern V was upregulated only during post-diapause. After heat shock, five different expression patterns were observed: pattern I responded weakly or not at all throughout diapause, pattern II responded weakly during the diapause stage but strongly at the onset of diapause and in the post-diapause period, pattern III was upregulated only during post-diapause, pattern IV was strongest during diapause, and pattern V was strongest only in early diapause. These complex expression profiles lead us to suggest that most of the sHSP genes are involved in the diapause process and that they may have multiple and important roles in different phases of this process.

Persistence of naturally occurring and genetically modified Choristoneura fumiferana nucleopolyhedroviruses in outdoor aquatic microcosms.

BACKGROUND: To assess the persistence of genetically modified and naturally occurring baculoviruses in an aquatic environment, replicate (three) outdoor, aquatic microcosms were spiked with spruce budworm viruses [Ireland strain of Choristoneura fumiferana multiple nucleopolyhedrovirus (CfMNPV) and the recombinant CfMNPVegt(-)/lacZ(+)] at a rate of 1.86 x 10(10) occlusion bodies (OBs) m(-2) of surface area. The presence of virus in water samples collected at various times after inoculation was determined by PCR amplification of baculoviral DNA extracted from OBs. RESULTS: Although UV radiation rapidly degrades baculoviruses under natural conditions, both viruses persisted above the level of detection (>100 OBs 450 microL(-1) of natural pond water) for at least 1 year post-inoculation, with little difference between the viruses in their patterns of persistence. CONCLUSION: The present microcosm study suggests that occlusion bodies of baculoviruses can persist in the flocculent layer of natural ponds. On disturbance, OBs could re-enter the main water column and thus be available for transport to new locations. Implications for environmental risk assessment are discussed.