The evolution of Brassica crops and wild relatives: phylogenetics, development and domestication
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The main goal of my dissertation is to understand the patterns and mechanisms underlying mustard (tribe Brassiceae, Brassicaceae) speciation in the Mediterranean while particularly addressing the morphological variation achieved during domestication of Cole crop (Brassica oleracea) members. I first reconstructed the phylogeny of the tribe Brassiceae (Brassicaceae). Phylogenetic analysis recovered eight well-supported clades in the tribe including a new African clade (Henophyton). Next, I estimated the tribe origin to be ca. 24 Mya in the Oligocene - Miocene boundary in the Saharo-Sindian region of the Mediterranean Basin. The origin of the tribe does not coincide with its western Mediterranean diversification center. Last, I looked at the global pattern of expressed genes in Brassica oleracea morphotypes: Kale, Cabbage and TO1000 to gain an understanding of the genome-wide differences among some of the vegetative phenotypes of this species. Differentially expressed developmental genes that regulated the vegetative to reproductive transition were abundant and present in all comparisons. Genes involved in leaf morphology (BLH3, BEL1, BLH1, BAM3, F10M23_30) and auxin transport and synthesis (AXR1, F12M16_13, LAX3, ATTIR1) were up-regulated in Kale. In conclusion, my work is the first to recovered a robust phylogenetic framework in which evolutionary hypotheses in the tribe Brassiceae and the cole crops can be tested.
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