GENETIC ABLATION OF FLORAL CELLS IN ARABIDOPSIS

A chimeric toxic gene consisting of the diphtheria toxin A chain gene fused to a promoter previously shown to direct pistil- and anther-specific expression was used to genetically target cell killing in transgenic Arabidopsis. Flowers of Arabidopsis transformants that carried the toxic gene fusion had distinct structural defects. The papillar cells at the stigma surface were stunted and were biosynthetically inactive. Anther development was also impaired by toxic gene expression, leading to abnormalities in anther dehiscence, pollen morphology, and pollen germination. The combined defects of pistil and anther rendered transformants that carried the toxic gene fusion self-sterile. However, the transformants were cross-fertile with untransformed plants: the viable pollen of ablated plants was rescued by wild-type stigmas, and, strikingly, the ablated papillar cells allowed the growth of wild-type pollen.