Cloning and characterization of DNA topoisomerase I gene Top1 from maize (Zea mays L.)

DNA topoisomerase I is a ubiquitous and essential enzyme in nature. Despite the biological importance, the molecular cloning of Top1 has not yet been reported in cereal crops. Herein, we presented the isolation and characterization of Top1 in maize. A total of 15 exons and 14 introns spanned 5325 bp genomic region of the maize topoisomerase I gene. The full-length 3265 bp cDNA of maize Top1 contained an ORF of 2715 bp encoding 904 amino acids with four characterized regions. The deduced amino acid sequence showed homology with Topo I proteins from other plants. Based on the human Topo I information, 3D structure of maize topoisomerase I was built. 169 putative cis-elements that are involved in hormone and light signalling responses, abiotic stress adaption were identified in the promoter region of Top1. Subcellular location in silico showed the position of Topo I in maize nuclei. Expression pattern analysis using MPSS method indicated maize Top1 expressed constitutively in all tissues and organs examined, with higher transcript levels in meristems, endosperm and anther.