Plant cytochrome P450 monooxygenases (CYP) constitute a large superfamily of heme-thiolate proteins, which are involved in a wide range of metabolic pathways. In this study, comparative genomic approaches were used to analyze tobacco CYP genes and their expression patterns. Based on analysis of the tobacco genomic DNA sequences that are currently available, 263 P450 genes that belong to 44 distinct clans were identified. EST evidence from 173 of the CYPs suggested that these genes are transcribed. Sequence features and secondary structures of the tobacco P450 genes were fur-ther analyzed through comparison with known P450 proteins. The expression profiles of 73 P450 genes were subsequently investigated by analyses of tobacco microarray data and RT-PCR. The results showed a variety of expression patterns of these genes in different tissues with a number of genes expressed in a tissue-specific manner. This study has set a founda-tion for further studies on functions of P450 genes in tobacco.
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