Deoxyribonucleic-acid sequences expressed at high levels in meristematic tissues of barley (Hordeum vulgare L.) have been cloned by differential hybridization. Five out of the seven cDNA clones studied showed homologies to histone genes H2a (two clones), H2b, H3 and H4. Their patterns of expression, as studied by RNA and in-situ hybridization, were typical for genes transcribed during cell division. A sixth cDNA clone, Sab2, had a 65.7% identity (on a protein basis) to L2-like ribosomal proteins of Escherichia coli and other lower prokaryotes. In a domain of 50 amino acids, the seventh clone, Sab35, showed 69.0% sequence identity to the ribosomal protein L21 of Rattus norvegicus. The Sab35 mRNA contained in its 5′-untranslated leader sequence small open reading frames, a feature pointing to a possible translational control. The Sab35 in-situ hybridization pattern was to a certain degree different from that of the histone-like clone Sab11: it detected transcripts not only in tissues that are associated with vegetative and reproductive apices but also in sub-apical regions. The visualization in situ of transcripts coded by Sab11, 35 and 44 is discussed as a possible technique for studying differential gene expression in barley meristematic tissues.
S. Köhler, I. Coraggio, D. Becker