A TOBACCO FLOWER-SPECIFIC GENE ENCODES A POLYPHENOL OXIDASE

Identification of pistil-expressed genes is an important step in under standing pistil development and function in plant reproduction. A toba cco stigma/style cDNA library was differentially screened and several cDNA clones were isolated. one of these tobacco genes, designated tobP 1, is characterized here. TobP1 encodes a protein highly homologous to plant polyphenol oxidases. Northern blot analysis of total RNA extrac ted from different organs and probed with tobP1 cDNA identified a sing le transcript that is exclusively present in flower organs (petals, st amens, and predominantly in pistils). The tobP1 gene is co-ordinately regulated during development in pistils and stamens, and is not induce d in mature leaves even under stress conditions. TobP1 belongs to a mu ltigene family, as reported for PPO in other plant species.