Ligand-Mediated cis-Inhibition of Receptor Signaling in the Self-Incompatibility Response of the Brassicaceae.
The inhibition of self-pollination in self-incompatible Brassicaceae is based on allele-specific trans-activation of the highly polymorphic S-locus receptor kinase (SRK), which is displayed at the surface of stigma epidermal cells, by its even more polymorphic pollen coat-localized ligand, the S-locus cysteine-rich (SCR) protein. In an attempt to achieve constitutive activation of SRK and thus facilitate analysis of self-incompatibility (SI) signaling, we coexpressed an Arabidopsis lyrata SCR variant with its cognate SRK receptor in the stigma epidermal cells of Arabidopsis (Arabidopsis thaliana) plants belonging to the C24 accession, in which expression of SRK and SCR had been shown to exhibit a robust SI response. Contrary to expectation, however, coexpression of SRK and SCR was found to inhibit SRK-mediated signaling and to disrupt the SI response. This phenomenon, called cis-inhibition, is well documented in metazoans but has not as yet been reported for plant receptor kinases. We demonstrate that cis-inhibition of SRK, like its trans-activation, is based on allele-specific interaction between receptor and ligand. We also show that stigma-expressed SCR causes entrapment of its SRK receptor in the endoplasmic reticulum, thus disrupting the proper targeting of SRK to the plasma membrane, where the receptor would be available for productive interaction with its pollen coat-derived SCR ligand. Although based on an artificial cis-inhibition system, the results suggest novel strategies of pollination control for the generation of hybrid cultivars and large-scale seed production from hybrid plants in Brassicaceae seed crops and, more generally, for inhibiting cell surface receptor function and manipulating signaling pathways in plants.
Section of Plant Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, New York 14953.
Titima
T
Tantikanjana
Section of Plant Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, New York 14953 jbn2@cornell.edu.
June B
JB
Nasrallah
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019607:Brassicaceae / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008024:Ligands; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011058:Pollen; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D060436:Self-Incompatibility in Flowering Plants / Q000502:physiology*; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D008024:Ligands; D009687:Nuclear Proteins; D010940:Plant Proteins; C522572:S-locus cysteine rich protein, Arabidopsis; D011494:Protein Kinases; C079832:S-receptor kinase