A tobacco flower-specific gene encodes a polyphenol oxidase

Identification of pistil-expressed genes is an important step in understanding pistil development and function in plant reproduction. A tobacco stigma/style cDNA library was differentially screened and several cDNA clones were isolated. One of these tobacco genes, designated tobP1, is characterized here. TobP1 encodes a protein highly homologous to plant polyphenol oxidases. Northern blot analysis of total RNA extracted from different organs and probed with tobP1 cDNA identified a single transcript that is exclusively present in flower organs (petals, stamens, and predominantly in pistils). The tobP1 gene is co-ordinately regulated during development in pistils and stamens, and is not induced in mature leaves even under stress conditions. TobP1 belongs to a multigene family, as reported for PPO in other plant species.