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UBC Theses and Dissertations

Effects of adaxial-abaxial signalling on leaf polarity Nowak, Julia S.


The unifying theme of this thesis is adaxial-abaxial or dorsiventral patterning in leaves. The adaxial-abaxial axis sets the thickness of a leaf and without the appropriate juxtaposition of the adaxial and abaxial domains, radialized leaves develop. The underlying genetic mechanisms of the development of these polarity defects started to be elucidated only over the past 20 years in the model Arabidopsis, in particular. I investigated this patterning in a variety of non-model species. Firstly, I investigated the variability of dorsiventral polarity in plants with naturally occurring radialized leaves including Allium, Nepenthes, Krishna fig, Pelargonium, several Cactaceae species, and popREVOLUTA mutant of a poplar hybrid. Subsequent chapters aimed to incorporate morphology and anatomy with molecular genetics in order to elucidate the underlying basis of the phenotype of interest in species that have not been used as model systems for leaf development, including canola and poplar. A novel mutant (lamina epiphylla, lip) was identified in canola, which has adaxialized leaves and leaf-derived organs. Some of the HD-ZIPIII candidate genes were sequenced in canola, but I was unable to determine the location of the LIP mutation. The rest of this thesis focuses on the abaxial greening and unifacial petiole phenotypes seen in some species of poplar that have isobilateral leaves (others in the genus have bifacial leaves). YABBY, KANADI, and HD-ZIPIII genes are some of the major contributors to setting proper adaxial-abaxial polarity and I investigated the relationships of these genes by identifying the orthologs in Arabidopsis, poplar, and eucalyptus (a genus that shares the abaxial greening phenotype with poplar). Further, I studied the species relationships within the genus Populus in order to establish the ancestral state of leaf type. I determined that bifacial leaves are likely derived within the genus. Finally, two poplar species (black cottonwood with bifacial leaves and hybrid aspen with isobilateral leaves) were compared on the basis of morphology, anatomy, and molecular genetics in order to determine the underlying basis of the abaxial greening and unifacial petiole phenotypes in hybrid aspen. I identified a subset of genes that may be involved in determining these phenotypes, but further investigation is needed.

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