title: Self-incompatibility triggers programmed cell death in Papaver pollen.
abstract: Sexual reproduction in many angiosperm plants involves self-incompatibility (SI), which is one of the most important mechanisms to prevent inbreeding. SI is genetically controlled by the S-locus, and involves highly specific interactions during pollination between pollen and the pistil on which it lands. This results in the rejection of incompatible ('self') pollen, whereas compatible ('non-self') pollen is allowed to fertilize the plant. In Papaver rhoeas, S-proteins encoded by the stigma component of the S-locus interact with incompatible pollen, triggering a Ca2+-dependent signalling network, resulting in the inhibition of pollen-tube growth. Programmed cell death (PCD) is a mechanism used by many organisms to destroy unwanted cells in a precisely regulated manner. Here we show that PCD is triggered by SI in an S-specific manner in incompatible pollen. This provides a demonstration of a SI system using PCD, revealing a novel mechanism to prevent self-fertilization. Furthermore, our data reveal that the response is biphasic; rapid inhibition of pollen-tube growth is followed by PCD, which is involved in a later 'decision-making' phase, making inhibition irreversible.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Vernonica E
authors.initials: VE
authors.lastname: Franklin-Tong
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D020013:Calcium Signaling; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D005306:Fertilization / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D035264:Flowers / Q000235:genetics / Q000502:physiology; D017343:Genes, Plant / Q000235:genetics; D010207:Papaver / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D011058:Pollen / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry / Q000378:metabolism; D013045:Species Specificity
chemical_list: D061945:Caspase Inhibitors; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases