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Three heat shock-responsive genes, Ofhsp70, Ofhsc70, and Ofhsp90, were identified in Omphisa fuscidentalis. These genes encode proteins with molecular weights of 70, 72, and 82 kDa, respectively, and were upregulated during heat shock. Ofhsp70 was expressed actively in the pre-diapause period, but its expression was low during diapause. While Ofhsc70 expression was low during pre-diapause and the first half of diapause, its expression increased greatly in the second half before diapause termination. In contrast, Ofhsp90 expression decreased by half during the transition to diapause and conspicuously decreased during late diapause. The results suggest that Ofhsp90 is associated with the maintenance of diapause and Ofhsc70 with the termination of diapause, whereas the expression of Ofhsp70 is unrelated to diapause. The insect molting hormone 20-hydroxyecdysone (20E) and juvenile hormone analog (JHA) caused increases in the mRNA expression of Ofhsc70, but not Ofhsp70 or Ofhsp90, in diapausing larvae. These transcriptional responses to 20E are consistent with the changes in ecdysteroid titer in the hemolymph relative to gene expression during diapause.

Trehalase is the hydrolytic enzyme that catalyzed the hydrolysis of trehalose to glucose. In this study, trehalase activity in the fungus-growing termite, Odontotermes feae Wasmann had been examined. Trehalase activity in digestive tract and carcass of O. feae was higher than that in wood-feeding termite, Coptotermes gestroi Wasmann. The intestinal tract of worker caste of O. feae was the main source of trehalase compared with that in salivary, fat body, and carcass. In particular, the highest activity was found in the midgut and hindgut parts. More specifically, the contents of midgut and hindgut had higher enzyme activity compared with that trehalase prepared from their epithelial tissue. The enzyme activity of gut trehalase in three different termite castes, worker, soldier, and reproductive, had been determined. The result showed that female alate had the highest activity, followed by worker, male alate, and soldier castes. Trehalose concentration in the reproductive caste was at lowest level, while soldier and worker contained the high trehalose concentration. This study indicates that high trehalase activity locates in the midgut and hindgut contents and change in trehalase activity in fungus-growing termite is caste-specific. Validamycin inhibited trehalase activity of O. feae in vivo and caused high mortality, indicating that this trehalase inhibitor is valuable tools for termite control.

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Abstract. The maize weevil, Sitophilus zeamais (Motschulsky), is a major pest of stored grain kernels. Irradiation is an established technique for controlling insects in stored grain and is a major stress factor affecting these insects. Since heat shock protein (hsp) genes respond to this stress, we proposed that hsps may be associated with irradiated stress tolerance in S. zeamais. The responses of the maize weevil to exposure to ultraviolet-C (UV-C) and microwave irradiation were assessed at four developmental stages: egg, larva, pupa and adult. The results revealed that exposure to UV-C (254 nm, < 8 h) did not affect the survival of the maize weevils; however, Szhsp70, Szhsc70 and Szhsp90 mRNA levels signifi cantly increased during the fi rst 1 h of UV-C exposure. The median lethal time (LT 50 ) of exposure to microwave irradiation indicated that the adult stage was more tolerant of microwave irradiation than the other developmental stages. Microwave irradiation enhanced the expression of the three hsps, but the intensity of up-regulation differed among the three genes, with Szhsp70 the most highly up-regulated. Our experiments revealed that UV-C and microwave irradiation infl uenced the expression profi le of hsp genes in S. zeamais. At the tissue level, the gene responses to UV-C and microwave irradiation varied greatly in different tissues.

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abstract. The bioinsecticidal effects of methanolic extracts of the leaves of castor bean, Ricinus communis, and papaya, Carica papaya, on the red flour beetle, Tribolium castaneum, were studied. More specifically, larval weight, larval mortality, percentage pupation, percentage adult emergence and F1 progeny production were recorded. We also studied the effects of the extracts on α-amylase activity and amylase gene expression in T. castaneum. The extracts of R. communis and C. papaya, which were administered in a diet, increased larval mortality and extended the durations of the larval and pupal periods. Feeding them an extract-treated diet also reduced the percentages of larvae that pupated and of adults that emerged and the number of F1 progeny. α-Amylase activity was inhibited and glucose content reduced in the larvae and adults of these insects. This inhibition of α-amylase activity by the R. communis and C. papaya extracts was concentration dependent in vitro. In addition, amylase gene expression was reduced in insects fed a diet containing C. papaya, but not R. communis extract. These results indicate that the bioinsecticidal effects of the leaf extracts are mediated by inhibiting the gene expression and activity of enzymes involved in sugar metabolism.

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