SummaryA novel endosperm-specific gene named Esr (embryo _surrounding region) has been isolated by differential display between early developmental stages of maize endosperms and embryos. It is expressed in a restricted region of the endosperm, surrounding the entire embryo at early stages (4 to 7 days after pollination, DAP) and everdecreasing parts of the suspensor at subsequent stages. The expression starts at 4 DAP and is maintained until at least 28 DAP. A minimum of three Esr genes are present in the maize genome and at least two of them map to the short arm of chromosome 1 at position 56. The Esr genes contain no introns and show no significant nucleotide or amino acid sequence homologies to sequences in the databases. The open reading frames encode basic proteins of 14 kDa with presumptive signal peptides at their Ntermini followed by a hypervariable and a conserved region. The gene product may play a role in the nutrition of the developing embryo or in the establishment of a physical barrier between embryo and endosperm.

SummaryIn cereal seeds, the aleurone layer and the embryo share several characteristics, including synthesis and accumulation of lipid bodies, desiccation tolerance and dormancy. A number of Balem transcripts present in both the barley deurone layer and the embryo have been cloned by differential screening of a cDNA library from aleurone layers of immature barley grains. The Balem clones constitute two subgroups, one for which the transcripts are detectable in aleurone layers and embryos of developing seeds only (B23D and Bl5C), and another for which transcripts are present also in germinating embryos and in maternal tissues (B12D, B14E and 831 E). Sequence analysis identified 8230 and B15C as the barley homologues of the 18 kDa oleosin of maize embryos (72% amino acid identity) and the dormancy-associated transcript pBS128 from Bromus secalinus (95% identity), respectively. In sifu hybridization experiments demonstrate that in the embryo, the B23D transcript is mainly present in the scutellum, whereas the B15C transcript is predominantly present in shoot and root apices. Using anther-derived embryos and embryogenic cell suspensions, it is demonstrated that the B23D and B15C transcripts can be used as molecular markers for somatic embryogenesis. The functions of the transcripts in the second Balem subgroup remain unknown. Further studies on the Balem transcripts may shed light on the molecular basis for the extensive similarities between the embryo and the aleurone layer of the endosperm in the grass family.

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