The Tomato Dwarf Gene lsolated by Heterologous Transposon Tagging Encodes the First Member of a New Cytochrome P450 Family

To transposon tag the tomato Dwarf ( D ) gene, a tomato line that carries a T-DNA containing the maize Activator (Ac) transposable element closely linked to 0 was pollinated with a stock homozygous for the d mutation. Hybrid seedlings were screened for dwarf progeny, and three independent dwarf lines were obtained. Two of these lines showed inheritance of a recessive phenotype similar to that conferred by the extreme dwarf (dx) allele. Variegation for the dwarf phenotype in one of these lines suggested that D had been tagged by Ac, Genomic DNA adjacent to Ac in these two lines was isolated by use of the inverse polymerase chain reaction, and the two insertions mapped -2 kb apart. Partia1 complementation of d was observed when the corresponding wild-type sequence was used in transformation experiments. A cDNA clone of D was sequenced, and the predicted amino acid sequence has homology to cytochrome P450 enzymes.