Developmental and Structural Section
Krosnick, Shawn , Potter, Daniel , Gasser, Charles .
CRABS CLAW as a Tool for Homology Assessment in Passiflora Nectaries.
Passiflora, a large genus of ca. 550 species, is known for its morphological diversity, displaying extensive variation in floral shape and size in relation to bird, bat, and insect pollination syndromes. Arguably, one of the most important floral features is the well-developed nectary as this structure provides pollinator rewards.¬†Almost all species of Passiflora¬†also possess elaborate extrafloral nectaries on bracts, stipules, petioles, and abaxial surfaces of leaves. Floral and extrafloral nectaries represent an underutilized source of phylogenetic data in the genus. This is due to the fact that homology assessment among nectary types is particularly difficult. Traditional criteria of positional similarity, special function, and transitional form are confounded by the degree of variability observed. Thus, the use of additional homology criteria that incorporate both anatomical and molecular data is critical to our understanding of the evolution of nectaries in Passiflora. In the present study, nectary evolution in Passiflora is examined using CRABS CLAW (CRC), a member of the YABBY gene family. Recent work suggests that CRC expression has been secondarily recruited as a key regulator of the development of both floral and extrafloral nectaries in the Eudicots. However, in Passiflora, CRC expression appears to be restricted to the floral nectaries alone. This not only suggests these extrafloral nectaries are not homologous with floral nectaries in Passiflora, but that they are also different from nectaries in other Eudicots studied thus far. Localization of CRC mRNA in Passiflora floral tissues shows a novel pattern with expanded domains of expression in the coronal filaments and the operculum. These data are examined within a phylogenetic context in order to explore appropriate homology concepts and ideas of character independence.
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1 - Rancho Santa Ana Botanic Garden, Research, 1500 North College Avenue, Claremont, CA, 91711, USA
2 - University of California, Davis, Department of Plant Sciences, Mail Stop 2, One Shields Avenue, University of California, Davis, California, 95616, USA
3 - University of California, Davis, Section of Molecular and Cellular Biology, One Shields Avenue, Davis, CA, 95616, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 2:45 PM