Expression patterns of three heat shock protein 70 genes among developmental stages of the red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae)

Three genes were identified encoding heat shock protein 70's in Tribolium castaneum (Herbst) and they were tentatively named as tchsp70 I, tchsc70 II, and tchsp70 III. Comparison of deduced amino acid sequences of tchsp70 I and tchsc70 II showed 99% identity. However, the amino acid sequence of tchsp70 III was only 58.5% identical to those of tchsp70 I and tchsc70 II. Stage-specific expression patterns of the tchsp70 were investigated in young larvae, old larvae, pupae, and adults of T. castaneum exposed for 1 h to 23 °C (control) or 40 °C (heat-shock). Northern blot and real-time quantitative PCR analyses were carried out to determine mRNA levels in each life stage. Transcripts of all three genes were detected by Northern blotting, and the sizes were 2.4- 2.2-, and 2.3-kb for tchsp70 I, tchsc70 II, and tchsp70 III, respectively. A 1.1- to 2.0-fold increased expression of tchsp70 I mRNA was found in heat-shocked developmental stages compared with the control. The expression of tchsc70 II mRNA among developmental stages was similar between heat-shocked and control insects, and the expression of tchsp70 III mRNA varied among developmental stages. Results suggest that the expression of tchsp70 I gene is heat-inducible, tchsc70 II is constitutive, and tchsp70 III is developmentally regulated in T. castaneum.