The accumulation of storage compounds during seed development ensures the survival of the young seedling, and also provides nutrition to humans and animals in the form of foods and feeds. The putative AP2/EREBP transcription factor WRINKLED1 (WRI1) is involved in the regulation of seed storage metabolism in Arabidopsis. A splicing mutant allele, wri1-1, caused the reduction of seed oil accumulation. Glycolysis was compromised in this mutant, rendering developing embryos unable to efficiently convert sucrose into precursors of triacylglycerol biosynthesis. Expression of the WRINKLED1 cDNA under the control of the cauliflower mosaic virus 35S-promoter led to increased seed oil content. Moreover, the ectopic expression of the WRINKLED1 cDNA caused the accumulation of triacylglycerols in developing seedlings. This effect depended upon the presence of glucose in the growth medium or other sugars readily metabolized to glucose. Oil-accumulating seedlings showed aberrant development consistent with a prolonged embryonic state.