| 摘要: | 低溫和寒害產生的冷逆境影響全球農作物的產量，所以很多植物演化出抵抗冷逆境
之分子機制包括維持RNA 分子的正常功能。RNA 解旋酶是一種以ATP 水解作為能量將
RNA 雙股解旋的酵素，它參與在與RNA 有關之機制，包括轉錄、核醣體生合成、
pre-mRNA 修飾、RNA 在細胞核與細胞質間運輸、轉譯、mRNA 降解和胞器中基因的表
現。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-box 蛋白，其
中已知功能的水稻DEAD-box 蛋白質很少，本論文主要目的在探討水稻中受冷逆境誘導
的DEAD-box 蛋白質OsRH42 基因為之生理功能，利用RNAi 轉殖株策略，發現三個
OsRH42 弱化表現之獨立轉殖株呈現對冷逆境極為敏感的性狀。OsRH42 位在細胞核中
的splicing speckle。進一步的研究結果顯示OsRH42 功能為維持Pre-mRNA 的正確
splicing， 一些對冷反應的基因， (OsSK12 (shaggy-related protein kinase) 、OsCIR1
(Circadian 1)、OsPRR95 (PSEUDO-RESPONSE REGULATOR)、OsPUB45 (PLANT U-BOX )、
OsEBF1 (EIN3-binding F-box protein 1 ) 、OsSPFH (SPFH/ PHB domain-containing
membrane-associated protein))，在冷逆境下OsRH42-Ri 轉殖株會發生錯誤splicing 的現
象。此外，在OsRH42 基因靜默轉殖株中CBF 基因表現增加。這些結果說明OsRH42
為水稻中表現受冷反應基因的正常splicing 不可或缺的RNA helicase，並且有助於水稻
對抗冷逆境。;Chilling and freezing temperatures negatively affect global crop production. Plants have
evolved several physiological and molecular adaptations to minimize damage from cold stress
programs. RNA helicases are enzymes that are able to unwind RNA duplex in an
ATP-dependent manner and play important roles in various aspects of RNA metabolism,
including transcription, pre-mRNA splicing, ribosome biogenesis, mRNA transport,
translation, and RNA decay. Rice, one of the most important crops in the world, contains at
least 62 different genes encode DEAD-box proteins. Herein, 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 three independent lines
of seedlings exhibited cold hypersensitive phenotype, regardless of whether or not they were
cold acclimated. Subcellular localization indicated that the OsRH42 localized into splicing
speckle. Cold-responsive genes, OsSK12 (shaggy-related protein kinase), OsCIR1 (Circadian
1), OsPRR95 (PSEUDO-RESPONSE REGULATOR), OsPUB45 (PLANT U-BOX ), OsEBF1
(EIN3-binding F-box protein 1 ), OsSPFH (SPFH/PHB domain-containing
membrane-associated protein) were misspliced in OsRH42 knockdown transgenic plants
under cold stress. Moreover, expression of cold response key regulators, CBF genes, were
increased in these OsRH42 knowndown lines, as compared to wildtype. There results
demonstrate that the cold-induced RNA helicase, OsRH42, is essential for splicing of
cold-responsive gene thereby contribute to cold stress tolerance in rice. |
