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.)

Abstract

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.

Keywords: HSP70; HSP90; Heat shock protein; Spruce budworm; Stress response.