Molecular cloning and expression of mRNAs encoding H1 histone and an H1 histone-like sequences in root tips of pea (Pisum sativum L.)

Two cDNA clones representing mRNAs, highly expressed in pea root tips, were isolated by mRNA differential display. Ribonuclease protection analyses showed different patterns of expression of these two messages in several pea tissues. Sequence analysis showed that the first clone, PsH1b-40, has 100% homology with a previously isolated H1 histone cDNA, PsH1b. However, it has an additional 30 nt at the 3′ end which is absent in PsH1b, suggesting possible multiple polyadenylation sites in the same mRNA. The second clone, PsH1b-41, encodes a deduced 19.5 kDa protein of 185 amino acids with an isoelectric point of 11.5. The putative globular domain of the encoded protein showed 67-71% residue identity with globular domains of 28 kDa pea PsH1b H1 histone and Arabidopsis thaliana H1-1 H1 histone. It has 9 repeating motifs of (T/S)XXK. In the C-terminal domain, there are four lysine-rich repeating motifs of SXK(T/S)PXKKXK which may be involved in chromatin condensation and decondensation. Southern blot analysis of nuclear DNA shows that PsH1-41 belongs to a multigene family.