MOLECULAR CHARACTERIZATION AND EXPRESSION OF A TOBACCO HISTONE H1 CDNA

We have isolated a 1104 bp tobacco cDNA clone (H1c12) which includes a n 846 bp open reading frame. This encodes a polypeptide of 282 amino a cid residues and represents the largest plant Hi histone identified so far. The structure of the deduced protein shows the classical tripart ite organization of the H1-type linker histones. The expression of the tobacco H1 histone gene(s) corresponding to the H1c12 cDNA clone was examined during different developmental stages. We found that, al the level of steady-state mRNA, expression of gene(s) encoding this H1 his tone was rapidly induced in germinating seeds. The H1 gene was express ed in all tissues examined. However, its expression tvas higher in tis sues known to contain meristematic cells. Furthermore, in the leaves o f mature plants accumulation of the H1 mRNA exhibits a very characteri stic oscillation. This latter finding indicates that, at least in full y developed plants, the expression of this type of H1 histone gene(s) is modulated by a diurnal cycle.