Abstract Detail

Development and Structure

Liu, Xiang [1], Xie, Deyu [1], Franks, Robert [1], Xiang, Qiu-Yun (Jenny) [1].

Down-regulating AP3 homolog expression showed floral and inflorescence changes leading to loss of the explosive pollen release in bunchberry (Cornus canadensis).

APETALA 3 is known to be a floral homeotic MADS-box protein regulating petal and stamen morphogenesis through interaction with PISTILATA in Arabidopsis. Mutations in either AP3 or PI resulted in replacement of petals by sepals and stamens by carpels. Constitutive expression of AP3 and PI from the CaMV35S promoter led to conversion of sepals into petals. Petal and stamen developments are clearly important to pollination success. In flowering plants with catapult mechanism for pollen release (e.g, Kalmia in Ericaceae and Cornus canadensis in Cornaceae), petal and stamen morphogenesis is crucial to the built-up of the elastic energy. In C. canadensis, the explosive pollen release depends on the formation of “X” structure of floral buds characterized by four connivent petals enclosing four mature anthers connected to bended and exerted filaments and a warn-like trigger on one of the petals. This feature and mechanism evolved uniquely in the bunchberry group of Cornus occurring in circumboreal regions where pollinators are scarce. Given the role of AP3 in Arabidopsis, one is curious about its potential role in the formation of this structure important to the bunchberries. We conducted experiments by down regulating the expression of AP3 homolog in C. canadensis using a hairpin structure and CaMV35S promoter through Agrobacterium-mediated transformation. We found that the inflorescences from approximately ten plants of five transgenic lines exhibited abnormal structure of the flowers and inflorescences, mainly the loss of the X structure and extra petaloid bracts within the inflorescences in addition to the four “involucral” petaloid bracts of the wild plants. However, in a few transgenic plants from two lines, these changes were not evident or vary among flowers of the same inflorescence. These experimental results suggest that the expression of AP3-homolg may be crucial to the formation of the “X” structure of flower buds, as well as to the suppression of bracts on the inflorescences. PCR and DNA sequencing confirmed the insertion of the hairpin structure. Further molecular characterization of the transgenic plants are being conducted to confirm the hypothesis.

1 - North Carolina State University, Department of Plant and Microbial Biology, Gardner Hall 2115, Raleigh, NC, 27695-7612, United States

Keywords:
Gene regulation
gene expression
genetic transformation
Cornus canadensis
flower development
Explosive pollen release.

Presentation Type: Oral Paper
Session: 49, Developmental and Structure II
Location: 205/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 4:15 PM
Number: 49003
Abstract ID:851
Candidate for Awards:None