title: The pollen S-determinant in Papaver: comparisons with known plant receptors and protein ligand partners.
abstract: Cell-cell communication is vital to multicellular organisms and much of it is controlled by the interactions of secreted protein ligands (or other molecules) with cell surface receptors. In plants, receptor-ligand interactions are known to control phenomena as diverse as floral abscission, shoot apical meristem maintenance, wound response, and self-incompatibility (SI). SI, in which 'self' (incompatible) pollen is rejected, is a classic cell-cell recognition system. Genetic control of SI is maintained by an S-locus, in which male (pollen) and female (pistil) S-determinants are encoded. In Papaver rhoeas, PrsS proteins encoded by the pistil S-determinant interact with incompatible pollen to effect inhibition of pollen growth via a Ca(2+)-dependent signalling network, resulting in programmed cell death of 'self' pollen. Recent studies are described here that identified and characterized the pollen S-determinant of SI in P. rhoeas. Cloning of three alleles of a highly polymorphic pollen-expressed gene, PrpS, which is linked to pistil-expressed PrsS revealed that PrpS encodes a novel approximately 20 kDa transmembrane protein. Use of antisense oligodeoxynucleotides provided data showing that PrpS functions in SI and is the pollen S-determinant. Identification of PrpS represents a milestone in the SI field. The nature of PrpS suggests that it belongs to a novel class of 'receptor' proteins. This opens up new questions about plant 'receptor'-ligand pairs, and PrpS-PrsS have been examined in the light of what is known about other receptors and their protein-ligand pairs in plants.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wheeler
authors.forename: Sabina
authors.initials: S
authors.lastname: Vatovec
authors.forename: Vernonica E
authors.initials: VE
authors.lastname: Franklin-Tong
mesh_terms: D001937:Brassica / Q000378:metabolism; D056426:Genetic Loci / Q000235:genetics*; D007178:Inbreeding; D008024:Ligands; D008954:Models, Biological; D010207:Papaver / Q000201:enzymology / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D011058:Pollen / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D008024:Ligands; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D012260:Ribonucleases