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Angiosperm seeds contain starch, protein, or lipid reserves that are mobilized to fuel postgerminative growth of the embryo, but relatively little is known about the regulation of this process. Seed storage reserves in Arabidopsis previously were believed to be contained exclusively in the embryo. Penfield et al. (pages 2705-2718) show that Arabidopsis stores significant amounts of lipid in the endosperm and that carbohydrates derived from this lipid arerequired for postgerminative seedling growth in the dark. The export of carbon from endosperm to embryo is found to be dependent on PHOSPHOENOLPYRUVATE CARBOXYKINASE1. In contrast with the embryo, the regulation of endosperm reserve mobilization and other endosperm-controlled processes is shown to be independent of ABA, demonstrating tissue-specific variation in ABA sensitivity and action in germinating Arabidopsis seeds. The cover shows endosperm cells expressing -glucuronidase under the control of the ISOCITRATE LYASE (ICL) promoter. ICL is a component of the glyoxylate cycle, which produces succinate used in gluconeogenesis.