Flavonols are required for successful fertilization in maize and petunia. Pollen lacking flavonols is unable to produce a functional pollen tube, but this defect can be reversed and pollen function "rescued" by the timely application of kaempferol, a flavonol aglycone. Biochemical complementation of mature petunia pollen is achieved: (1) at pollination by wild type stigma exudate; (2) by adding powdered kaempferol to the stigma or pollen at pollination; and (3) by supplementing pollen with flavonol aglycones in vitro. The last method forms the basis of a sensitive bioassay used to identify compounds that induce pollen germination. It also provides a model system for a focused and systematic investigation of flavonol-stimulated pollen germination. This investigator proposes to combine biochemical and molecular approaches to characterize flavonol synthesis in developing anthers, the subsequent metabolic fate of flavonols during pollen germination, and the genes that respond to the flavonol stimulus. This information is crucial to understanding how small, planar molecules stimulate pollen germination. An understanding of the factors regulating fertilization in higher plants is of interest not only in terms of reproductive biology, but can lead to the mechanisms to regulate fertility and fecundity.
