Histone genes in higher plants: Organization and expression

The general structure of the plant histone genes has been deduced from the comparison of the nucleotide sequences of ten H3 and H4 genes of maize (3 H3 and 3 H4) and Arabidopsis thaliana (2 H3 and 2 H4). The five H3 and five H4 genes encode the same proteins, respectively. The 5′‐flanking regions contain the classical histone gene‐specific consensus sequences. In addition, a conserved octanucleotide CGCGGATC was found in all plant histone genes at 200–250 nucleotides before the initiation codon. All six maize H3 and H4 genes are transcribed during early germination as shown by nuclease S1 mapping and reverse transcriptase primer extension experiments. The mRNA 5′‐ends are located within the consensus sequence CCAA/CT/C. The 3′‐ends lack the classical T‐hyphenated dGC‐rich palindromic structure and possess long nontranslated sequences. In both plants the multiple copies of the H3 and H4 genes are organized into multigenic families. The genes of each family show a similar proximal environment, suggesting that they originate from the duplication of a common ancestor.