A novel DNA polymerase homologous to Escherichia coli DNA polymerase I from a higher plant, rice (Oryza sativa L.)

摘要

A novel DNA polymerase, designated as OsPoll-like, has been identified from the higher plant, rice (Oryza sativa L. cv. Nipponbare). The OsPoll-like cDNA was 3765 bp in length, and the open reading frame encoded a predicted product of 977 amino acid residues with a molecular weight of 100 kDa. The OsPoll-like gene has been mapped to chromosome 8 and contains 12 exons and 11 introns. The encoded protein showed a high degree of sequence and structural homology to Escherichia coli pol I protein, but differed from DNA polymerase γ and θ. The DNA polymerase domain of OsPoll-like showed DNA polymerase activity. Subcellular fractionation analysis suggested that the protein is localized in the plastid. Northern and western blotting, and in site hybridization analyses demonstrated preferential expression of OsPoll-like in meristematic tissues such as shoot apical meristem, root apical meristem, leaf primordia and the marginal meristem. Interestingly, no expression was detected in mature leaves, although they have a high chloroplast content. These properties indicated that OsPoll-like is a novel plant DNA polymerase. The function of OsPoll-like is discussed in relation to plastid maturation.