Abstract Detail

Anatomy and Morphology

Denbigh , Georgia Lee [1], Dauphinee, Adrian N.  [2], Fraser, Meredith S. [1], Lacroix, Christian R. [3], Gunawardena, Arunika [1].

Investigating the origin of the induction signal(s) involved in developmentally regulated programmed cell death in the lace plant (Aponogeton madagascariensis).

Programmed cell death (PCD) is a genetically encoded method for the targeted deletion of unwanted cells. One fascinating example of developmentally regulated PCD is perforation formation in lace plant (Aponogeton madagascariensis) leaves, which produces holes positioned equidistantly between longitudinal and transverse veins at a precise time and location. The intracellular dynamics and time course of perforation formation have been well documented in the lace plant, including the disappearance of anthocyanin, accumulation of reactive oxygen species (ROS) and caspase-like activity. However, the induction signal(s) involved in perforation formation is not known. Therefore, the objective of this study is to investigate the induction signal(s) and their origin in developmentally regulated PCD in the lace plant. We hypothesized that leaf vasculature plays an important role in the induction of lace plant PCD. We tested our hypothesis by treating sterile cultures of lace plants with polar auxin-transport inhibitor, NPA, to alter vein pattern and determine the effect on the PCD process. If our hypothesis holds, typical events that occur during lace plant PCD would deviate with the addition of the NPA. Whole plants with a minimum of two to three perforated mature leaves were treated with an optimized concentration of NPA and grown simultaneously with control plants. Following seven days of growth, leaves from each plant were excised and ordered chronologically in order to record leaf lengths and widths of leaves that developed before and after treatment application. Micrographs of early-stage leaves were taken to analyze anthocyanin presence, vein patterning and perforation formation. A spectrophotometric assay was performed to determine anthocyanin levels and superoxide (a ROS molecule) accumulation was detected using nitroblue tetrazolium (NBT) stain. The release of cytochrome c (cyt-c) from the mitochondria into the cytosol is a well-established event during PCD in several plant systems, thus, the investigation of cytosolic cyt-c in lace plant leaf tissues was performed through a cytosolic fractionation and subsequent western-bolt analysis. Plants treated with NPA displayed reduced perforations, abnormal vein patterning and atypical areoles compared to control plants. Altering the initial event of vasculature differentiation was seen to influence downstream events in the developmentally regulated pathway, such as low anthocyanin abundance, low ROS accumulation and no release of cyt-c, thus inhibiting PCD in NPA-treated plants. Results obtained from these experiments indicate that vein patterning and auxin-transport are crucial for the induction of developmentally regulated PCD in the lace plant.

Related Links:
Programmed cell death research in the lace plant

1 - Dalhousie University, Department of Biology, 1355 Oxford Street, Halifax, NS , B3H 4R2, Canada
2 - Swedish University of Agricultural Sciences, Department of Molecular Sciences, Almas Allé 8, Uppsala, Uppsala County, SE-750 07, Sweden
3 - University of Prince Edward Island, Department of Biology, 550 University Ave, Charlottetown, PE , C1A 4P3, Canada

Keywords:
Lace plant
Leaf Development
Programmed cell death
Vein patterning .

Presentation Type: Oral Paper
Session: 13, Anatomy and Morphology II
Location: 113/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 1:30 PM
Number: 13001
Abstract ID:369
Candidate for Awards:Cinq Mars Award