Cellular mechanisms for pollen tube growth inhibition in gametophytic self-incompatibility

Abstract

Self-incompatibility (SI) is a mechanism used by angiosperms to prevent self-fertilization. Here we review current knowledge of two different gametophytic SI systems at the cellular level, revealing different mechanisms that interfere with pollen tube growth. In the Solanaceae, Rosaceae, and Scrophulariaceae, SI is controlled by an interaction between a pistil component, S-RNase, and a pollen component, an F-box protein, SLF/SFB. While a variety of models focused on ubiquitylation have been explored, it is still unclear exactly how the S-RNase based system operates at the cellular level. In Papaver, entirely different S-proteins act as signalling ligands that trigger a Ca 2+-dependent signalling cascade that results in programmed cell death (PCD). Although the pollen S-receptor has not been identified in Papaver, the mechanisms involved in inhibiting incompatible pollen are better understood. © Springer-Verlag Berlin Heidelberg 2006.