植物可藉由感受糖濃度的改變來調整生長、發育和對抗環境逆境，而且糖感應機制會與植物對抗逆境的訊息交互作用，然而目前探討糖感應機制、環境逆境與植物基因表現的研究僅著重於轉錄層次，對於後轉錄層次上的調控，則所知甚少。mRNA 穩定度為後轉錄層次調控中的重要一環，mRNA 降解速率的決定步驟在mRNA poly(A) tail 的 deadenylation，因此deadenylation 發生的時間決定mRNA 的命運。已知CCR4-CAF1 複合體為deadenylase，參與mRNA poly(A) tail 的降解，但仍然未知它的確切生理功能與調控方式。我們先前從玉米與水稻中分離出CAF1 類似的基因:ZmCAF1s 與OsCAF1s，並發現不同的CAF1s 參與調控不同特定基因mRNA 的poly (A) tail，進而影響基因在糖訊息及逆境中的表現。本計畫探討水稻OsCAF1s 在基因表現後轉錄階段所扮演的角色，及它在糖訊息與環境逆境中的生理功能，我們將分析大量表現及RNAi 之OsCAF1s 轉殖水稻，研究受糖調控基因的表現、poly(A) tail 長度與RNA 穩定度，以達成下列三個目標。一、探討OsCAF1s 在糖類訊息傳導的生理功能。二、瞭解OsCAF1s 在不同環境逆境的生理功能及其應用。三、分析水稻細胞OsCAF1s 的生化活性，探討其受質的專一性。本研究成果將可建構植物在糖類訊息傳導路徑、環境逆境耐受性與基因調控之詳細網絡，並應用於水稻對抗環境逆境之農業生物科技上。Sugars are evolutionarily conserved signaling molecules that regulate various genes involved in developmental stages and adaption of abiotic stresses. Cross-talk between sugar and abiotic stress signaling has been evidenced at transcriptional level. However, little is understood about the mechanism of mRNA degradation, which is also important for regulation of gene expression in sugar-abiotic stress signaling networks. It is known that deadenylation of poly(A) tail is the first and rate-limiting step during mRNA degradation. And therefore CCR4-CAF1complex with deadenylase activity is proposed to play a prominent role in mRNA degradation. However, physiological functions of CCR-4CAF1 are still not clear. We identified the CAF1 genes from maize and rice, ZmCAF1s and OsCAF1s, respectively. Our recent evidences suggested that plant CAF1s have deadenylase activity and function at the first step of mRNA degradation in plants. Further investigations are required to elucidate specific roles of plant CAFs in mRNA degradation of genes in sugar-abiotic stress signaling networks. Therefore, both loss- and gain-of function approaches for these CAFs will be used and further microarray analysis will be applied in this proposed research. The following three specific aims are intended to study OsCAFs. 1. To demonstrate of biological functions of OsCAF1s in sugar signaling transduction pathway. 2. To address whether using mRNA degradation to resist stressful environmental conditions is practical in rice through manipulation of activities of OsCAF1H and OsCAF1B in transgenic rice for stress tolerance. 3. To analyze in vitro RNase activities of OsCAF1s by recombinant protein approach in E.coli. In addition to our understanding about transcriptional regulation in sugar-abiotic stress signaling networks, we will have more clear view in post-transcriptional regulation after combining results from these proposed works. Through knowledge of both transcriptional and post-transcriptional gene regulation in rice, we are able to design a practical genetic engineering strategy to develop stress tolerant rice plants. 研究期間：10008 ~ 10107
