Differential expression of Histone H3 gene in tea (Camellia sinensis (L.) O. Kuntze) suggests its role in growing tissue.

Histone proteins are integral part of chromatin and their expression is typically linked to DNA replication in the S phase of cell cycle. Histone H3 is one of the four histones, along with H2A, H2B and H4, which forms the eukaryotic nucleosome octomer core. Using differential display of mRNA and rapid amplification of cDNA ends (RACE), a full-length Histone H3.1 cDNA (CsH3) was isolated from tea leaves. The open reading frame consisted of 411 nucleotides and deduced amino acid sequence comprised of 136 amino acid residues. CsH3 shared 79-82% and 98% identity at nucleotide and amino acid sequences, respectively with Histone H3 isolated from other plant species. During active-growth period of tea, higher expression was observed in apical buds that decreased gradually with increasing age of the leaf. During dormancy season, the expression of CsH3 was severely down-regulated in all the leaves studied. CsH3 was found to be down regulated in response to drought stress and ABA treatment and up-regulated by GA(3) treatment. A positive association of CsH3 abundance with active cellular growth suggested its role in plant growth and development.