TRANSCRIPTS ENCODING AN OLEOSIN AND A DORMANCY-RELATED PROTEIN ARE PRESENT IN BOTH THE ALEURONE LAYER AND THE EMBRYO OF DEVELOPING BARLEY (HORDEUM-VULGARE L) SEEDS

In cereal seeds, the aleurone layer and the embryo share several chara cteristics, including synthesis and accumulation of lipid bodies, desi ccation tolerance and dormancy. A number of Balem transcripts present in both the barley aleurone layer and the embryo have been cloned by d ifferential screening of a cDNA library from aleurone layers of immatu re barley grains. The Balem clones constitute two subgroups, one for w hich the transcripts are detectable in aleurone layers and embryos of developing seeds only (B23D and B15C), and another for which transcrip ts are present also in germinating embryos and in maternal tissues (B1 2D, B14E and B31E). Sequence analysis identified B23D and B15C as the barley homologues of the 18 kDa oleosin of maize embryos (72% amino ac id identity) and the dormancy-associated transcript pBS128 from Bromus secalinus (95% identity), respectively. In situ hybridization experim ents demonstrate that in the embryo, the B23D transcript is mainly pre sent in the scutellum, whereas the B15C transcript is predominantly pr esent in shoot and root apices. Using anther-derived embryos and embry ogenic cell suspensions, it is demonstrated that the B23D and B15C tra nscripts can be used as molecular markers for somatic embryogenesis. T he functions of the transcripts in the second Balem subgroup remain un known. 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.