title: S-RNase uptake by compatible pollen tubes in gametophytic self-incompatibility.
abstract: Many flowering plants avoid inbreeding through a genetic mechanism termed self-incompatibility. An extremely polymorphic S-locus controls the gametophytic self-incompatibility system that causes pollen rejection (that is, active arrest of pollen tube growth inside the style) when an S-allele carried by haploid pollen matches one of the S-alleles present in the diploid style. The only known product of the S-locus is an S-RNase expressed in the mature style. The pollen component to this cell-cell recognition system is unknown and current models propose that it either acts as a gatekeeper allowing only its cognate S-RNase to enter the pollen tube, or as an inhibitor of non-cognate S-RNases. In the latter case, all S-RNases are presumed to enter pollen tubes; thus, the two models make diametrically opposed predictions concerning the entry of S-RNases into compatible pollen. Here we use immunocytochemical labelling of pollen tubes growing in styles to show accumulation of an S-RNase in the cytoplasm of all pollen-tube haplotypes, thus providing experimental support for the inhibitor model.
authors.affiliation: Biology Department, University of Montreal, Quebec, Canada.
authors.forename: D T
authors.initials: DT
authors.lastname: Luu
authors.forename: X
authors.initials: X
authors.lastname: Qin
authors.forename: D
authors.initials: D
authors.lastname: Morse
authors.forename: M
authors.initials: M
authors.lastname: Cappadocia
mesh_terms: D011058:Pollen / Q000378:metabolism*; D012098:Reproduction; D012260:Ribonucleases / Q000378:metabolism*; D019657:Solanaceae / Q000201:enzymology / Q000502:physiology*
chemical_list: D012260:Ribonucleases