Plant Cell Monographs Volume 8, 2007, pp 57-71
Date: 24 Mar 2007

The Embryo Surrounding Region

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There is converging evidence in maize, wheat, barley, Arabidopsis and other species that the endosperm in proximity of the embryo is cytologically different from the remaining endosperm. Gene expression restricted to this embryo surrounding region (ESR) reinforces the notion of a specialized endosperm domain at least in maize and Arabidopsis. The ESR is a dynamic structure that is set apart prior to cellularisation and starts to disappear with the onset of reserve accumulation in the developing seed. During later developmental stages it is frequently succeeded by a liquid filled space around the embryo. While the cytological characteristics of the regions surrounding the embryo are quite similar between the species analyzed, their functional equivalence has not yet been established. Possible functions of the ESR include nutrition or defense of the embryo as well as signaling between the embryo and the endosperm.