1. Implications
In the future we will use this data to identify candidate genes responsible for altered flowering time,
reproductive output, and plant architecture at elevated [CO2]. Identifying genes within genomic regions
responsible for the aforementioned factors at elevated [CO2] is key for a more complete understanding of
the responses of plants in future elevated [CO2] environments and will help us to better understand the
mechanisms behind these responses.
Thanks to the Howard Hughes Medical Institute, Dr. Nicholas Nicolaides, and Biology Department of St. Joseph’s
University for funding this research project.
.
Objective
To identify regions of the Arabidopsis genome that are responsible for altered
flowering time, plant architecture, and reproductive output at elevated [CO2]
Methods
• We used 108 RILs (recombinant inbred lines) of Arabidopsis derived from two parental genotypes: Landsberg
Erecta (Ler) and Columbia (Col) developed by Lister and Dean (1993)
• We grew 8 replicates of each line in growth chambers maintained at 400 and 1000 ppm [CO2] with a 14-hour
photoperiod and day/night growth temperatures of 25 ºC and 18 ºC, respectively
• We measured the flowering time of each individual
• Using QTL CARTOGRAPHER (Basten et al. 1998), we conducted a composite interval mapping analysis using
forward-backward regression with a maximum of 5 background parameters, a window size of 10cM, and an
experiment-wise LOD (log of the odd ratio) threshold significance level that was set by computing 1,000
permutations of flowering time
• We analyzed flowering time for significant QTL by [CO2] interactions using the JZmapqtl module that
simultaneously analyzed the significant QTL based upon the average flowering time for each RIL at each CO2
treatment
• With the results of the JZmapqtl module, we detected genomic regions exhibiting QTL by [CO2] interactions
Since the beginning of the Industrial Revolution, atmospheric
carbon dioxide concentration ([CO2]) has risen from 270 to 380
ppm and is predicted to reach 700 ppm within 50-80 years. CO2
serves as the primary carbon substrate for photosynthesis. Plants
grown at elevated [CO2] commonly exhibit increased
photosynthetic rates, biomass accumulation, and reproductive
output. In addition plants may exhibit altered developmental
timing (e.g. time to flowering) that may alter processes at the
population, community, and ecosystem levels.
Introduction
Changes in global atmospheric CO2 concentration
(IPCC 2001).
Background
• Flowering is a critical milestone in the life cycle of plants that
depending on its timing can have major effects on
reproductive success
• Upon surveying the literature, we found that 57% of wild
species and 62% of crop species exhibit altered flowering
times in response to elevated [CO2] (Springer & Ward, 2007)
• We found genetic variation in the flowering times of field-
collected genotypes of Arabidopsis thaliana grown at 700 ppm
CO2 relative to 380 ppm CO2
• This intra-specific variation indicates a potential for natural
selection to act on flowering time in future elevated [CO2]
environments
• Understanding the mechanism(s) responsible for changes in
flowering time at elevated [CO2] will increase our ability to
predict the impact of elevated [CO2] on future ecosystems
Flowering time of 10 randomly selected genotypes of
Arabidopsis originating from widely distributed
geographical regions grown at current (380 ppm) and
elevated (700 ppm) CO2. (Springer & Ward, 2007)
Previous Results
•We found two similar significant QTLs between plants grown at current and elevated [CO2] on
Chromosomes 2 and 5.
• We found 2 significant QTL that differed between plants grown at current and elevated [CO2]. The red
arrow on Chromosome 2 of the elevated [CO2]-grown plants indicates this QTL
Current Study
• In the process of determining the effect of flowering time on
reproductive output.
• More specifically, if changes in CO2 concentration cause an effect in
the number of seeds per silique as well as in the number of siliques
per plant.
•Counting siliques on the main flowering part of A. thaliana, as well
as on secondary flowering shoots and their branches.
•In addition, we are currently isolating genomic regions responsible
for altered plant architecture and reproductive output of elevated
[CO2]-grown Arabidopsis compared to plants grown at current [CO2]
The Response of Flowering Time and Plant Architecture in Arabidopsis thaliana to Elevated [CO2]
Briena E. Healy1 and Clint J. Springer1
1Department of Biology, St. Joseph’s University, Philadelphia, PA USA
Current [CO2] Elevated [CO2]
16
20
24
28
32 Ireland
Norway
Sweden
Portugal
Austria
BC, Canada
Cape Verdi
Tadjikistan
Ukraine
Belgium
380 700
TimeofFlowering(d)
[CO
2
] (ppm)
QTL found in elevated [CO2] only