The Papaver self-incompatibility pollen S-determinant, PrpS, functions in 'Arabidopsis thaliana'

Many angiosperms use specific interactions between pollen and pistil proteins as “self” recognition and/or rejection mechanisms to prevent self-fertilization. Self-incompatibility (SI) is encoded by a multiallelic S locus, comprising pollen and pistil S-determinants [ [1] and [2]]. In Papaver rhoeas, cognate pistil and pollen S-determinants, PrpS, a pollen-expressed transmembrane protein, and PrsS, a pistil-expressed secreted protein [ [3] and [4]], interact to trigger a Ca2+-dependent signaling network [ [5], [6], [7], [8], [9] and [10]], resulting in inhibition of pollen tube growth, cytoskeletal alterations [ [11], [12] and [13]], and programmed cell death (PCD) [ [14] and [15]] in incompatible pollen. We introduced the PrpS gene into Arabidopsis thaliana, a self-compatible model plant. Exposing transgenic A. thaliana pollen to recombinant Papaver PrsS protein triggered remarkably similar responses to those observed in incompatible Papaver pollen: S-specific inhibition and hallmark features of Papaver SI [ [11], [12], [13], [14] and [15]]. Our findings demonstrate that Papaver PrpS is functional in a species with no SI system that diverged ∼140 million years ago [16]. This suggests that the Papaver SI system uses cellular targets that are, perhaps, common to all eudicots and that endogenous signaling components can be recruited to elicit a response that most likely never operated in this species. This will be of interest to biologists interested in the evolution of signaling networks in higher plants