Poly(A) tail的縮短也被稱為deadenylation，在真核生物中被認為是mRNA降解的速率決定步驟。CCR4-associated factor 1s (CAF1s) 在酵母菌與哺乳類動物中，則被認為是降解mRNA最為重要的酵素之一，然而在植物中關於CAF1的研究則是少之又少，因此我們針對水稻的OsCAF1s去做研究，我們發現水稻的OsCAF1B對於αAmy3 mRNA 的降解與deadenylation的過程，扮演了一個相當重要的角色。OsCAF1B基因會受到糖的誘導，因此我們利用大量表現OsCAF1B與失去deadenylase活性的OsCAF1B突變株，來探討其與受糖抑制基因αAmy3之間的關係，結果發現，大量表現OsCAF1B會加速αAmy3 mRNA的降解，而在大量表現失去deadenylase活性的OsCAF1B突變株中則會延緩其降解，並且在αAmy3 mRNA poly(A)長度也各別呈現相反的影響。此外，OsCAF1B也參與在水稻植株抵抗低溫逆境當中，在持續性大量表現OsCAF1B轉殖小苗，我們發現其呈現抗低溫的外表型，並且發現OsCAF1B deadenylase的功能對於水稻低溫耐受性是必要的，其改變了後期低溫反應轉錄活化因子的基因表現。總結以上發現，我們證實水稻OsCAF1B除了參與αAmy3 poly(A) tail deadenylation之外，還提供水稻抵抗低溫的能力。;Poly(A) tail shortening, also termed deadenylation, is the rate-limiting step of mRNA degradation in eukaryotic cells. The CCR4-associated factor 1s (CAF1s) was shown to be one of the major enzymes for catalyzing mRNA deadenylation in yeast and mammalian cells. However, the functions of CAF1 proteins in plants are poorly understood. Herein, we find that OsCAF1B plays a vital role in sugar-induced αAmy3 mRNA degradation and deadenylation. OsCAF1B expression was induced by sugar. Using gain of function and dominant negative mutation analysis, it was determined that sugar-induced αAmy3 mRNA degradation was accelerated in transgenic rice cell lines overexpressing OsCAF1B, whereas it was delayed in dominant negative mutation lines. Moreover, OsCAF1B overexpression and dominant negative mutation lines exhibited αAmy3 mRNA poly(A) tail shortening and extension, respectively. OsCAF1B also functioned in rice seedlings tolerance to cold stress. In transgenic rice seedlings, constitutive overexpression of OsCAF1B presented an enhanced cold tolerance phenotype. OsCAF1B deadenylase is essential for cold tolerance in rice. The enhancement of cold tolerance in transgenic rice was shown to be associated with the altered expression of late cold response transcription factors. These findings indicate that OsCAF1B participates in poly(A) tail deadenylation and acts in adaptation to cold stress in rice.
