Introduction

The process of pollination and fertilisation in flowering plants involves a series of interactive events between male and female cells. One of the earliest stages in the process of fertilisation is the recognition, and acceptance or rejection, of pollen grains alighting on the stigma of the recipient plant. Self-incompatibility (SI) involves these processes. Prevention of self-fertilisation is accomplished by the inhibition of pollen that has the same incompatibility phenotype as that of the stigma on which it lands. These highly specific recognition events are both developmentally expressed and tissue-specific. Investigation of the molecular basis of the expression and regulation of the S-genes, and the mode of action of their products, therefore, provides a model system for the study of gene expression and cellular recognition in flowering plants.

There is currently considerable interest in the elucidation of the molecular basis of SI and much work has been carried out in an attempt to identify the molecules involved in this interaction, especially those on the female side. S-linked glycoproteins from styles and stigmas, and the genes that encode them, have been identified and cloned. Less progress has been made with the pollen component. We aim to look at what is currently known about SI, with a view to examining what is known about the mechanism of this response.

What is known about the pistil and pollen components?

Identification and characterisation of stigmatic S-linked glycoproteins

There have been a number of studies carried out on proteins which have been isolated from stigmatic/stylar tissues.