Characterization of Two Small Heat Shock Protein Genes ( and ) from , and Their Expression Regulation during Diapause.

, a periodic but devastating wheat pest that escapes temperature extremes in summer and winter by undergoing obligatory diapause. To determine the roles of small heat shock proteins (sHsps) in diapause of we characterized two genes, and , from this species. Both SmHsps contained the conserved α-crystallin domain and the carboxy-terminal I/VXI/V motif of the sHsp family. had one intron while had none. Quantitative PCR revealed that expression decreased after diapause initiation, but substantially increased during transition to post-diapause quiescence. In contrast, expression was not affected by entry of diapause, but was clearly up-regulated during summer and winter. Short-term more severe heat-stress (≥35 °C) of over-summering larvae or cold-stress (≤-5 °C) of over-wintering larvae could stimulate higher expression of both genes, and was more responsive to cold stress while was more sensitive to heat stress. Notably, transcription of , but not , in diapausing larvae was inducible by 20-hydroxyecdysone (20E). Recombinant SmHsp17.4 and SmHsp20.3 proteins also displayed significant chaperone functionality. These findings suggest that both play key roles in stress tolerance during diapause; and 20E-regulated was also likely involved in diapause termination.