MOLECULAR-CLONING, SEQUENCE-ANALYSIS AND DIFFERENTIAL EXPRESSION OF AN INTRON-CONTAINING GENE ENCODING TOMATO HISTONE H1

A tomato genomic clone has been identified which encodes histone H1. T he deduced polypeptide is 287 amino acids in length, and exhibits the tripartite organization typical of histones H1. The central globular d omain is highly similar to those regions from other H1 molecules, and the carboxyl-terminal domain contains a repeating hexapeptide motif, v ariants of which are conserved among H1 molecules. RNA gel blotting re vealed that histone H1 mRNA is expressed at higher levels in organs wh ich contain meristematic tissue and/or which have a high proportion of actively cycling cells. DNA gel blotting and dot-blot hybridization s tudies revealed that histone H1 in tomato is encoded by a small gene f amily. By employing the polymerase chain reaction on genomic DNA and o n cDNA, it was determined that the gene is interrupted by an intron. T he location and approximate length of the intron are conserved in both the tomato and Arabidopsis genes, with the intron separating the 'nos e' region (encoded by exon 1) from the central globular domain (exon 2 ). The promoter region was found to contain several conserved sequence motifs which likely participate in the regulation of the gene.