cDNA cloning of heat shock proteins and their expression in the two phases of the migratory locust

The high population density of insects is often a stress factor. Insects synthesize heat shock proteins (Hsps) in response to the impacts of stress through molecular chaperone activity. Locust solitary and gregarious phases occur at low and high population density, respectively. In this study, we compare the expression profiles of the Hsp genes in the two phases of the migratory locust in an attempt to examine the role of Hsps in adaptation to high density populations. The full length cDNAs of Hsp20.5, 20.6, 20.7, 40, 70 and Hsp90 of the migratory locust were cloned and sequenced. The expressional differentiation of the six Hsps in mRNA levels between solitary and gregarious locusts was observed. Results from real-time PCR indicate that the six Hsps are expressed throughout all developmental stages except in the early stage embryo. The expression levels of the six Hsps were significantly upregulated in gregarious locusts. The expressional variations among certain organs, such as the head, thorax and leg of fifth instar nymphs in gregarious locusts were also higher than those in solitary ones. These observations suggest that population density may be an important factor in determining Hsp expression in the locust.