To understand the expression pattern of the S RNase gene in the floral tissues associated with self-incompatibility(SI), promoter region of S11 RNase gene were constructed, and introduced into Nicotiana tabacum using Agrobacterium-mediated transformation. Northern blot analysis revealed that the GUS gene was expressed in the style, anther, and developing pollen of all stages in each transgenic tobacco plant. The developing pollen expressed the same amount of GUS mRNA in all stages in transgenic tobacco plants. In addition, histochemical analysis showed GUS gene expression in vascular bundel, endothecium, stomium, and tapetum cells during pollen development in transgenic plants. From these results, it is speculated that SI of Lycopersicon peruvianum may occur through the interactin of S RNase expressed in both style and pollen tissues.