Most higher plants reproduce sexually, consequently factors that influence fertilization have a significant impact on reproductive success. Despite that little is known of the cellular and molecular events surrounding pollen germination, tube growth, and deposition of the sperm into the embryo sac. We established that flavonoids, normally found in pollen, are essential for successful fertilization. Flavonoid-deficient pollen is unable to germinate but this defect can be "rescued" by the exogenous application of micromolar quantities of a specific class of flavonoids leading to germination and tube growth in vitro and normal fertilization and seed-set in vivo. How do these small, hydrophobic molecules induce pollen germination? The basic tool to address this question if the pollen rescue assay. To begin, the accumulation site and intracellular transport mechanisms of flavonoids will be determined by localization and kinetic analysis. The identical flavonoid required for germination also stimulates transcription; this suggests a molecular mechanism of flavonoid action and requires that these genes be identified by cloning and sequencing. This will lead to a model of flavonoid action during pollen germination. The product of this proposal will extend the knowledge of basic reproductive biology and provide information useful in the design of mechanisms to manipulate plant fertility.
