| Summary: | 博士 === 國立臺灣大學 === 生化科技學系 === 103 === 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.
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