Signaling in pollen-pistil interactions

A complex set of cell-cell interactions is required to achieve fertilizatio n. The pollen grain must be recognized by the pistil, take up water, and gr ow a pollen tube directionally through the style in order to deliver the sp erm to the ovule. In many families of flowering plants, self-fertilization can be prevented by recognition mechanisms that allow self-pollen rejection by the pistil. The self-incompatibility response is under the genetic cont rol of a single multi-allelic locus, the S (Self-incompatibility) locus. Th ere are two major classes of self-incompatibility systems. Gametophytic sel f-incompatibility has been well characterized in the Solanaceae and in the Papaveraceae, while sporophytic self-incompatibility has been well characte rized in the Brassicaceae. In this review article, we present recent advanc es in understanding the signals mediating pollen recognition and pollen tub e growth, in both compatible and incompatible interactions.