The search for components of the self-incompatibility signalling pathway(s) in Brassica napus

The Brassica self-incompatibility system is controlled by a multi-allelic S receptor kinase (SRK) gene. Upon contact between self-incompatible pollen and the stigmatic papillae at the surface of the pistil, this receptor kina se is predicted to initiate a signalling pathway in the stigmatic papilla l eading to the rejection of the self-incompatible pollen. Several different approaches have been taken to determine the molecular events occurring in t he stigmatic papillae upon activation of the self-incompatible response. Ex amination of cytosolic calcium levels, electrical responses, cytoskeletal o rganization, and callose deposition in the stigmatic papillae during compat ible and incompatible pollinations fail to reveal any responses specific to self-incompatibility. However, the identification of stigmatic proteins wh ich interact with the SRK; kinase domain has led to the characterization of a novel protein called ARC1 which appears to be a substrate for the S rece ptor kinase and is a positive effector of the self-incompatibility response . (C) 2000 Annals of Botany Company.