Modeling developmental plasticity in variable environments through gene duplication: a case for phytochromes and gibberellin3-oxidases’ role in temperature-dependent seed germination
Abstract
Seed germination is a critical developmental transition in plants and is regulated
by complex combinations of environmental cues that restrict its timing to occur over
the widest possible range of conditions suitable for subsequent survival. To investigate
the genetic mechanisms by which seeds achieve this restriction, we characterized the
functional diversification of two duplicated gene families, phytochromes and gibberellin3-oxdiases,
involved in temperature dependent seed germination. Germination responses were recorded
of single and multiple PHY and GA3ox functional knockout mutants after exposure to
various temperature treatments reflecting seasonal conditions. PHYE was the only copy
necessary for germination in cold temperatures after a cold imbibition treatment,
while PHYB was an important contributor to germination after seeds did not experience
a dormancy-breaking imbibition treatment. GA3ox2 was the most important GA3ox contributor
to germination in a range of temperature conditions while GA3ox1 and GA3ox3 appeared
to contribute redundantly to germination with GA3ox2, the first evidence of GA3ox3’s
role during temperature-dependent germination. The diversification of these genes
during germination suggests that gene duplication plays an important role in regulating
a plant’s response to complex seasonal environments. We then constructed a basic two-step
genetic pathway model to investigate how environmental sensitive and/or functionally
diversified duplicated genes are able to restrict a physiological response, such as
germination, to combinations of environmental cues. Identical diversifications in
duplicated upstream and downstream genes resulted in the most precise restriction
of responses around optimal environmental conditions. Moreover, environmental sensitive
diversification within duplicated genes was required in order to elicit a physiological
response to more than one set of optimal environmental conditions supporting the importance
of diversified duplicated genes in achieving developmental plasticity in variable
seasonal environments.
Description
Honors Thesis awarded High Distinction in the Biology major at Duke University
Type
Honors thesisDepartment
BiologyPermalink
https://hdl.handle.net/10161/8105Citation
Gibbs, David Corley (2013). Modeling developmental plasticity in variable environments through gene duplication:
a case for phytochromes and gibberellin3-oxidases’ role in temperature-dependent
seed germination. Honors thesis, Duke University. Retrieved from https://hdl.handle.net/10161/8105.Collections
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