Question

The male component of gametophytic self-incompatibility exhibited by Nicotiana alatais an F-box protein that is part of an E3 ubiquitin ligase.  Based on information given in lecture and lecture notes, propose a model to explain how the F-box protein and the S-RNase mediate self-incompatibility.  Be sure to account for the action of the proteins in compatible and incompatible interactions.  

Answer 1

Self incompatibility is genetically coded measure to control breeding between same species. It prevent inbreeding and increase the chance of variation in plants. In Nicotiana alatois. it is controlled by highly allelic S locus. If proteins from S locus in male matches with S locus expressed in Style it prevents the breeding. In Nicotiana alatois a Style specific extranuclear RNase and 10 proteins of F-box DD genes. F-box protein are competent of SCF complex takes ubiquitin from E2 ubiquitin conjugating enzyme and transport it to a target protein. F-box protein bind and ubiqutylate the S-RNase which causes degradation by proteosomic pathway and causes self incompatibility due to inability of interaction between male and female gametophyte.