Expression of a globulin-like protein gene, Gea8, in somatic and zygotic embryos

A carrot gene, Gea8 (Globular embryo abundant), has been identified that en codes a novel seed protein that is abundantly expressed in embryos from the globular: to the cotyledon stages and in endosperm of maturation-stage see ds, Analysis of the Gea8 gene revealed that it encodes a protein with appro ximately 47% sequence similarity (25% sequence identity) to both dicot and monocot globulins, a class of seed storage proteins. However, the Gea8 prom oter region lacks some of the key regulatory elements characteristic of oth er known globulins, especially the 'G box' sequence. Analysis of Gea8 mRNA accumulation during both somatic and zygotic embryogenesis showed that mRNA for this gene accumulates by the; globular stage of embryogenesis and reac hes a high abundance by the heart stage that is sustained throughout embryo development. Expression is also high in the developing endosperm of seeds of both carrot and Arabidopsis. In addition, analysis of the! developmental and spatial expression of the? Gea8 gene, using several Gea8 promoter/GUS fusion constructs, suggests that the promoter contains at least two separab le regions directing the spatial accumulation of Gea8 mRNA in the heart and torpedo stages of embryogenesis. These studies suggest that Gea8 is a new form of seed protein that is expressed early in embryo development, initial ly in an embryo-specific pattern, and subsequently in both the embryo and t he endosperm through regulation by a complex promoter.