S-LOCUS GLYCOPROTEINS ARE EXPRESSED ALONG THE PATH OF POLLEN TUBES INBRASSICA PISTILS

In Brassica, self-incompatibility has been correlated with S-locus gly coproteins (SLG) localized at the site of pollen rejection, the stigma tic papillae. In this paper we present immunocytochemical evidence tha t during development of the pistil SLG proteins accumulate not only in the stigmatic papillae, but also in the transmitting tissue of stigma , style and ovary, along the pathway followed by the pollen tube. This observation was confirmed by the biochemical characterization of styl ar and ovarian SLG proteins and by the detection of SLG transcripts in style/ovary tissues by polymerase chain reaction analysis. Thus we de monstrate similarities between the pattern of SLG gene expression in B rassica (sporophytic self-incompatibility system) and that of S produc ts in Nicotiana (gametophytic self-incompatibility system) which may r eflect relationships between the self-incompatibility systems. An acti ve role of SLG gene products during the pollen-tube growth in the pist il is discussed.