| 摘要: | 基因表現的過程中，RNA 分子不僅是基因資訊的訊息傳遞者，有些RNA 也扮演著細胞執行功能時之 催化角色。RNA 可以為長鍊或短鍊單股，形成的2 級與3 級結構，正確的結構可以確保RNA 分子進 行正確的功能。DEAD-box RNA helicases 為細胞中維持或修改RNA 分子正確構型的重要蛋白質，依 據標的RNA，DEAD-Box RNA helicase 參與了細胞核中的轉錄、pre-mRNA 的接合、rRNA 的生合成、 細胞核到細胞質的運輸、轉譯、和RNA 降解。 文獻報告已指出，當細胞處於環境逆境時，必然要改變自身的分子運作及生理機轉之分子機制包 括維持RNA 分子的正常功能，因此改變RNA helicases 的表現或活性，是細胞維持正常基因表現與逆 境耐受力的重要關鍵之一，唯該方面的研究，主要集中在雙子葉植物。例如，阿拉伯芥的DEAD-Box RNA helicase LOS4 參與調控冷逆境耐受性所需的基因表達；又如， DEAD-Box RNA helicaseSTRS1 和ATRS2 被認為是阿拉伯芥中的非生物逆境信號傳遞網絡的上游負調節因子。水稻為世界上重要糧 食作物，至少含有62 種不同的基因編碼DEAD-boxRNA 解旋酶。先前，我們發現OsRH42 為受冷逆 境誘導的基因，而且OsRH42 基因靜默的轉殖水稻呈現不耐低溫外表型， OsRH42 位在細胞核中的 splicing speckle，顯示OsRH42 功能為維持pre-mRNA 的正確splicing 同時也是水稻對抗冷逆境之正調 控因子。因此，我們將進一步釐清OsRH42 參與在水稻對抗冷逆境之分子機制，了解OsRH42 參與之 RNA 分子之細胞生理反應，釐清它與水稻對抗冷逆境的關係。 本計畫將完成下列三分項目標。第一，釐清OsRH42 在水稻除參與抗冷逆境以外，是否參與抗熱 與抗缺水逆境。第二，釐清提高水稻中OsRH42 的表現是否增加水稻抵抗冷逆境的能力。第三，探討 OsRH42 在細胞RNA 分子之細胞生理反應之角色、所影響之基因及與水稻抗冷逆境之關係。相信以我 們研究室在植物DEAD box RNA helicases 的研究成果，將可順利達成計畫所設定的目標，並藉由這些 研究逐步解開不同的DEAD box RNA helicases 在水稻中的所扮演的角色，以及它與抗冷逆境的關係。 ;As well as being a messenger for gene expression, RNA can also be as a catalytic molecule in cell. The correct structure of RNA molecules ensures that function correctly. DEAD-box RNA helicases are enzymes that can rearrange RNA secondary structure, and therefore control RNA metabolism and gene expression, such as transcription, pre-mRNA, rRNA synthesis, nucleus to cytoplasm transport, translation, and RNA degradation. Plants are sessile, require complex and coordinated gene expression to survive under stress environments. Recently, the plant DEAD-box RNA helicases related to stress tolerance have been evidenced. For example, a cold stress-regulated DEAD-box RNA helicase, LOS4, was found to regulate a set of gene expression that is required for freezing tolerance. Meanwhile, Arabidopsis STRS1 and ATRS2, encoding DEAD-box RNA helicases, were found to function as an upstream negative regulator of both ABA-dependent and ABA-independent abiotic stress signaling networks. It is plausible to hypothesize that the DEAD-box RNA helicases play important roles in plants to cope with adverse conditions. Despite the DEAD-box RNA helicases can be crucial for plant stress tolerance, the studies are major focus in Arabidopsis. Little is known whether crop plants employ similar mechanisms to overcome stressful environments, and whether manipulation of DEAD-box RNA helicase activities could enhance crop tolerance. Previously, we identified a rice DEAD-box RNA helicase gene, OsRH42, which expression was induced by cold stress. The OsRH42 knockdown transgenic plants were generated by RNAi approach and results were showed that three independent lines of seedlings exhibited hypersensitive to cold stress phenotype, regardless of whether or not they were cold acclimated. Subcellular localization indicated that the OsRH42 localized into splicing speckle. There results imply that the cold-induced RNA helicase, OsRH42, is essential for splicing of cold-responsive gene mRNA and contribute to rice tolerance to cold stress. This proposed research focus to study the detail molecular mechanism of the OsRH42 function in cold stress resistance in rice. Therefore, the functions of the OsRH42 in physiological, cellular and molecular responses to a variety of cold stresses and the targets of OsRH42 will be elucidated. Furthermore, overexpression of OsRH42 in transgenic rice plants will be tested for their adapt ability under cold stress. Combining the results from these studies, we will have knowledge in OsRH42-mediated cold tolerance pathway and to develop a cold stress tolerant rice plants. |
