dc.description.abstract | We focused on studying the mechanism of gene induction of Oshsp18.0 under treatment of L-azetidine-2-carboxylate (AZC), a proline analog, in this study. Organisms respond to elevated temperature by up-regulating heat shock genes. Not only in temperature stress, but also in various kinds of chemical irritations and pH change induces expression of heat shock genes. Induction of heat shock genes results in accumulation of heat shock proteins. Accumulated heat shock proteins enhances thermotolerance or resistance to following severe stress. AZC induces expression of small heat shock protein genes, however, it causes sever ion-leakage to a comparable level of lethal heat stress treatment. By pre-treatment of nonlethal heat stress, the ion-leakage dropped. Hence, acclimation enhances thermotolerance while AZC causes severe ion-leakage. We chose one of the nine class I small heat shock protein genes in rice, Oshsp18.0, for detailed analysis via RT-PCR. Oshsp18.0 is expressed under heat stress, AZC, Cu2+, Cd2+ or As3+. Oshsp18.0 is expressed at a higher level under heat stress, AZC, As3+ and lower level under Cu2+ and Cd2+. Even change of pH slightly induces expression of Oshsp18.0. As a prline analog, AZC is likely to incorporate into polypeptides which causes misfolded protein and unfolded protein response. Pre-treatment of inhibitor of protein de novo synthesis, cycloheximide, gene expression of Oshsp18.0 delayed under AZC treatment which was not observed in other treatments. This implies different gene regulation mechanism is involved under AZC treatment. Induction of heat shock genes depends on the interaction of transcription factor and regulatory element located on the promoter region of heat shock genes. A 9-base-pair element, AZRE (5’ -CGTCCAGGAC- 3’), was previously identified in the promoters of Oshsp18.0 and Oshsp17.3. AZRE responded to AZC treatment specifically. To identify the transcription factor(s) that specifically interact with AZRE, we used yeast one-hybrid technology to screen cDNA library which was prepared from AZC treatment. Of the candidates, genes involved in the unfolded protein response were obtained. For its repetition, 10-kDa chaperonin (10Cpn), was selected for further analysis. 10Cpn is a constitutively expressed gene as shown via RT-PCR. In vitro binding assay showed no interaction with AZRE. Other candidate genes must be tested in the future. | en_US |