Protein function and interactions in Gametophytic Self-Incompatibility: Collaborative recognition of S-RNase in vivo.

摘要

My dissertation is based on studies of Gametophytic Self-Incompatibility (GSI), a system that allows plants to reject "self" pollen while accepting "non-self" pollen, thus preventing inbreeding and promoting genetic diversity in populations. In GSI, pollen grains deposited on the stigma of the floral pistil germinate and begin to grow through the transmitting tract tissue of the style. As the pollen tubes grow through the transmitting tract, they import recognition variants of a secreted protein known as the S-locus ribonuclease (S-RNase). If there is a match of recognition specificity between the pollen tube and the imported S-RNase, the S-RNase will degrade pollen-tube RNA, inhibiting protein synthesis & pollen tube growth. Conversely, if there is no match between pollen tube and S-RNase, the action of the S-RNase is inhibited, and the pollen tube continues to grow normally to the ovary.;Inside pollen tubes, non-self S-RNases are recognized by the SCF SLF complex comprising multiple variants of the pollen-recognition protein named SLF, along with three other proteins: SSK1, SBP1 and Cullin-1. I have been using protein-interaction assays (BiFC assays) based on the reconstitution of a fluorescent protein, to study interactions between components of the SCFSLF complex and S-RNase.;Previous studies revealed that multiple SLF genes collaborate during non-self S-RNase recognition. Based on my data, SLF10 and to a lesser extent, SLF1, SLF3, SLF4 and SLF5 showed interaction with different S-RNase constructs. In addition, data in my study suggests that a "bridge" protein may be needed to stabilize proteins interactions between SLF and S-RNase. The work that has been completed will lead to a better understanding of self versus non-self recognition in pollination. An understanding of GSI mechanisms should also lead to the ability to manipulate breeding barriers in agricultural crops such as tomatoes, potatoes and fruit trees.