Abstract: The indoleacetic acid-lysine synthetase (iaaL) gene of Pseudornonas syringae subsp. savastanoi was fused to a rice Rchl0 promoter and introduced into tobacco plants. The expression pattern of this chimeric Rchl0-iaaL gene in the transgenic plants was studied, and the endogenous levels of indoleacetic acid (IAA) were assayed with the high-performance liquid chromatography (HPLC) method. The results showed that the Rchl0 promoter could direct the high level expression of the iaaL gene in young inflorescences, fully bloomed flowers, and immature fruits, resulted in a decrease of the IAA levels by 32%–82%. The transgenic plants displayed decreased apical dominance, enlongated stamens, abnormal inflorescences and fruits. The transgenie plant pYL614-T14, in which the endogenous IAA levels in inflorescences were reduced by 82 %, displayed extremely abnormal inflorescence with only two flowers and a much higher potential of vegetative growth than that of the controls after flowering. These Rchl 0-iaaL gene transgenic tobacco plants would pro- vide valuable materials for further studies of physiological functions of IAA in reproductive development.

Key words: Floral-specific promoter, IAA-lysine synthetase gene, Transgenic tobacco, Flower development