From canonical to new model systems: The future of plant development
Lacroix , Christian , Shafiullah, M. D. , Bourque, Laura .
Myriophyllum aquaticum: a system for comparative developmental studies of leaves, from genes to morphology.
Myriophyllum aquaticum is a member of Haloragaceae family and is generally aquatic in nature. It is a simple-leaved plant with highly dissected leaves consisting of several lobes. It can produce two morphologically different forms of leaves based on whether they are aerial or aquatic. A comparative developmental study of aerial and aquatic leaves of M. aquaticum was conducted using scanning electron microscopy. Differences in quantitative parameters for the shoot apical meristem (SAM) and leaf primordia confirm that the two different growth forms begin to diverge from their early stages of development. Differences in epidermal cell morphology, extent of lobe development, and presence or absence of appendages on the leaves are the most obvious qualitative manifestations of varying growth conditions. This study also sets the context for a comparison of KNOTTED1-LIKE HOMEOBOX (KN1) gene expression patterns during leaf development between aquatic and aerial growth forms of M. aquaticum. The role of KN1 in maintaining cells in an undifferentiated meristematic state is well documented, and studies of the expression patterns of this gene during plant development continue to provide insight into leaf morphogenesis. In M. aquaticum, the expression of MaKN1 (KN1 homologue in this species) was detected in the SAM and expressed ubiquitously throughout primordia of plastochrons (leaf positions) 1 to 3 (P1-3). As lobes develop, MaKN1 becomes localized to recently emerged lobe primordia, and the level of expression gradually decreases as lobes develop basipetally. Our in situ hybridization study revealed that the expression patterns of MaKN1 varied between aerial and submerged growth forms. More specifically, MaKN1 expression in aquatic forms of M. aquaticum was observed to extend beyond P8, as typically observed in aerial forms. We believe that a prolonged expression (beyond P8) of MaKN1 plays an important role in the formation of more numerous and elongated lobes, as well as ectopic meristems that produce appendage-like structures on leaves of aquatic growth forms of M. aquaticum.
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1 - UNIVERSITY OF PRINCE EDWARD ISLAND, Department Of Biology, 550 UNIVERSITY AVE, CHARLOTTETOWN, PE, C1A 4P3, Canada, 902/566-0320
2 - University Of Prince Edward Island, Biology, 550 University Avenue, Charlottetown, PE, C1A 4P3, Canada
Presentation Type: Symposium or Colloquium Presentation
Location: Delaware A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 5:00 PM