Molecular basis of the incompatibility mechanism in Papaver rhoeas L.

In this study we have begun to dissect the molecular mechanism of the self-incompatibility reaction of Papaver rhoeas. In order to gain an insight into the cellular activities, which lead to the inhibition of pollen tube growth following a self-incompatible response, we have been studying the effects of various metabolic inhibitors on pollen-stigmatic extract interactions in vitro. The results indicate that both transcription and glycosylation are required for the full inhibition of pollen tube growth during an incompatible response in P. rhoeas. The ability of actinomycin D to alleviate an incompatible reaction suggests that during the response pollen gene expression is induced; we have evidence that this is indeed the case and have identified novel proteins produced in the pollen which are associated with the incompatibility response. These findings give a clear indication that de novo transcription of pollen genes which are specific to this response, play an important role in the inhibition of pollen tube growth in this species. This provides a significant step towards the elucidation of the mechanism whereby pollen tube growth is arrested following an incompatible reaction in this species. Ribonuclease assays have revealed that, in contrast to the S-linked glycoprotein of Nicotiana alata, there is no detectable ribonuclease activity that correlates with the presence of the functional stigmatic S-gene product in P. rhoeas.