Initial characterization and expression pattern analysis of common tobacco (Nicotiana tabacum) metal tolerance protein C4 and 11 genes

The complete coding sequences of common tobacco metal tolerance protein C4 and 11 genes were amplified by RT-PCR. The tobacco metal tolerance protein C4 gene encodes a protein of 471 amino acids which shares high identity with the metal tolerance protein C4 of four species-wood tobacco (97%), nicotiana tomentosifonnis (93%), potato (85%) and capsicum annuum (84%). The tobacco metal tolerance protein 11 gene encodes a protein of 399 amino acids which shares high identity with the metal tolerance protein 11 of six species-wood tobacco (99%), nicotiana tomentosiformis (99%), lycopersicon pennellii (92%), lycopersicon esculentum (92%), potato (92%) and capsicum annuum (92%). Prediction of transmembrane helices showed that metal tolerance protein C4 and 11 might be two transmembrane proteins. Phylogenetic analysis revealed that the common tobacco metal tolerance protein C4 and 11 genes both have a closer genetic relationship with the wood tobacco metal tolerance protein C4 and 11 genes. Computer-assisted analysis showed that metal tolerance protein C4 gene is structured in 13 exons and 12 introns. Metal tolerance protein 11 gene is structured in 6 exons and 5 introns. The gene expression profile analysis indicated that the common tobacco metal tolerance protein C4 and 11 genes were differentially expressed in root, flower, leaf and stem. The expression of metal tolerance protein 11 gene was ubiquitously higher than that of metal tolerance protein C4 gene in all detected tissues.