Julia Nowak

Graduate student (PhD)
Completed: Aug. 2012


Research topic: Effects of adaxial-abaxial signaling on leaf polarity.

Research interests:

  • General: Leaf evolution, development, dorsiventral polarity controls.
  • Variation among the adaxial-abaxial polarity controls in poplar leaf development.
  • Developmental controls of unifacial leaves.
  • Controls of organ/vasculature polarity in the Brassica napus (canola) lip mutant.
  • Role of KNOX during palm leaf development.
  • Developmental morphology of palm leaves, particularly of the genera Chamaedorea and Chamaerops.

Email address: ac.cbu.egnahcretni|jkawon#ac.cbu.egnahcretni|jkawon


  • M.Sc., University of Guelph, Guelph, Ontario (2005-2007)
  • B.Sc. Hon., University of Toronto, Toronto, Ontario (2001-2005)

Research projects:

My primary interest 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.

My further research 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 the location of the LIP mutation has not been determined, to date.

The remainder of my work focuses on the abaxial greening and unifacial petiole phenotypes seen in some species of poplar that have isobilateral leaves (while 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 (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 derived within the genus. Finally, I compared two poplar species (black cottonwood with bifacial leaves and hybrid aspen with isobilateral leaves) 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 warranted.



  • Nowak, J.S., Q.C.B. Cronk, et al. In Preparation. Phylogenomics and expression of dorsiventral leaf polarity genes in forest trees.
  • Nowak, J.S. and Q.C.B. Cronk. In Preparation. Abaxial greening phenotype in hybrid aspen.
  • Nowak, J.S., E.J. Gilchrist, I.A.P. Parkin, G.W. Haughn, and Q.C.B. Cronk. In Submission. Lamina epiphylla: a novel adaxialized leaf mutant of canola.
  • Nowak, J.S., J. Ono, and Q.C.B. Cronk. 2010. Anatomical study of an aquatic mustrard: Subularia aquatica (Brassicaceae). Aquatic Botany 93: 55-58.
  • Nowak, J., A. Nowak, and U. Posluszny. 2009. Developmental comparison of leaf shape variation in three Chamaedorea species. Botany 87(2): 210-221. (Journal cover)
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