Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The current assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n=14) containing 32,928 and 36,697 protein-coding genes, respectively. The Petunia lineage has experienced at least two rounds of paleohexaploidization, the older gamma hexaploidy event, which is shared with other Eudicots, and the more recent Solanaceae paleohexaploidy event that is shared with tomato and other Solanaceae species. Transcription factors that were targets of selection during the shift from bee- to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral color patterns and pollination systems. The high quality genome sequences will enhance the value of Petunia as a model system for basic and applied research on a variety of unique biological phenomena

Protein function and interactions in gametophytic self-incompatibility : collaborative recognition of S-RNase in vivo

Advisors: Thomas L. Sims.Committee members: Barrie Bode; Melvin Duvall; Gabriel Holbrook; Timothy Robbins.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.Ph.D. (Doctor of Philosophy

Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n = 14) containing 32,928 and 36,697 protein-coding genes, respectively. The genomes reveal that the Petunia lineage has experienced at least two rounds of hexaploidization: the older gamma event, which is shared with most Eudicots, and a more recent Solanaceae event that is shared with tomato and other solanaceous species. Transcription factors involved in the shift from bee to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral colour patterns and pollination systems. The high-quality genome sequences will enhance the value of Petunia as a model system for research on unique biological phenomena such as small RNAs, symbiosis, self-incompatibility and circadian rhythms