阿拉伯芥ICE1在離層酸依賴性路徑之功能研究

Abstract

由酵母菌雙雜合篩選到INDUCER OF CBF EXPRESSION 1 (ICE1) 會與HEPTAHELICAL PROTEIN 1 (HHP1) 的N端產生交互作用。ICE1調控冷逆境訊息傳導被認為是一種離層酸非依賴性 (ABA-independent) 的路徑。本論文發現ICE1可能也會參與離層酸依賴性 (ABA-dependent) 的訊息傳導路徑。當ICE1的T-DNA插入突變株ice1-2播種在缺乏糖的1/2 MS培養基上時，幼苗長成率會明顯下降；但培養基中添加56 mM葡萄糖之後，幼苗長成率就可以回復到與野生型相同的程度。除了糖依賴性的性狀之外，ice1-2的發芽率和幼苗長成率對高濃度葡萄糖的感受性也比野生型高。另外ice1-2也觀察到對離層酸有過敏感 (hyper-sensitive) 性狀，推測ice1-2對葡萄糖的過敏感性狀可能是經由離層酸訊息傳導路徑產生的。葡萄糖和離層酸處理會使幼苗時期的ice1-2中兩個與離層酸訊息傳導有關基因ABA-INSENSITIVE 3 (ABI3) 和ABA-INSENSITIVE 4 (ABI4) 的表現量有過度誘導的現象。除了會參與冷逆境反應、氣孔發育和胚乳降解之外，本論文發現ICE1是離層酸依賴性路徑的一個負調控子。

INDUCER OF CBF EXPRESSION 1 (ICE1) was identified as an interaction partner of N-terminus of HEPTAHELICAL PROTEIN 1 (HHP1) by yeast two-hybrid. ICE1 mediates the cold stress signal via an abscisic acid (ABA)-independent pathway. A possible role of ICE1 in ABA-dependent pathways was identified in this study. Seedling growth was severely reduced in a T-DNA insertion mutant of ICE1, ice1-2, when grown on 1/2 MS medium lacking sugars, but was restored to wild-type (WT) levels by supplementation with 56 mM glucose. In addition to this sugar-dependent phenotype, germination and establishment of ice1-2 were more sensitive to high glucose concentrations than in the WT. Hypersensitivity to ABA was also observed in ice1-2, suggesting its sensitivity to glucose might be mediated through the ABA signaling pathway. Glucose and ABA induced much higher expression of two genes related to ABA signal transduction, ABA-INSENSITIVE 3 (ABI3) and ABA-INSENSITIVE 4 (ABI4), in ice1-2 than in the WT during establishment. In summary, in addition to its known roles in regulating cold responses, stomatal development, and endosperm breakdown, ICE1 is a negative regulator of ABA-dependent responses.