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Using Genome-wide Approaches to Understand Natural Variation in Plant Fitness- and Defense- Related Traits

Ji, Hao (2014) Using Genome-wide Approaches to Understand Natural Variation in Plant Fitness- and Defense- Related Traits. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Plants have developed sophisticated defense networks to defend against their enemies and increase their fitness. However, there is often significant natural variation in plant fitness- and defense- related traits. If high levels of defense and reproduction are important, then why do plants not all have the highest possible values for these traits? One possible explanation is that these traits are costly to produce and allocation to one trait limits the resources available for another. Such tradeoffs are likely to be very important in understanding why phenotypic variation is maintained in natural populations. However, the genetic mechanisms that underlie them remain poorly understood. Coding regions of known defense- and seed- related genes are typically highly conservative in their sequences, suggesting that sequence differences in those genes are not responsible for the observed phenotypic variation. How then do plants achieve large phenotypic differences in these traits?

In my dissertation studies, I have dissected the genetic architecture underlying tradeoffs in defense and reproductive traits in the model plant, Arabidopsis thaliana and identified tradeoffs in a worldwide collection of wild Arabidopsis populations between a defense trait, leaf trichome number, and a reproductive trait, mass per seed. I found that two traits were negatively correlated at a major trichome-related locus, ETC2, which encodes a transcription factor. I also performed a Genome-wide Association (GWA) study searching novel candidate genes accounting for the observed variation in resistance to a bacterial pathogen, Pseudomonas syringae DC3000 and found that one of the candidate genes, AtABCG16, appears to assist plant resistance through its effect on abscisic acid-signaling in leaves.

Collectively, my work has taken advantage of reverse genetic mapping, traditional genetic techniques ,and bioinformatical analysis to improve our knowledge of plant natural variation. Moreover, my work suggests that the genetic basis of tradeoffs may involve both transcription factors and hormonal signaling. These findings are novel and are likely to explain why phenotypic variation persists in important defense traits. These results will therefore be important for predicting how these traits will respond to environmental change and how they can be manipulated in agricultural crops.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ji, Haohaj13@pitt.eduHAJ13
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairTraw, Brianmbtraw@pitt.eduMBTRAW
Committee MemberBarth,
Committee MemberKalisz, Susankalisz@pitt.eduKALISZ
Committee MemberTonsor, Stephen Jtonsor@pitt.eduTONSOR
Committee MemberRebeiz, Markrebeiz@pitt.eduREBEIZ
Date: 31 January 2014
Date Type: Publication
Defense Date: 27 August 2013
Approval Date: 31 January 2014
Submission Date: 22 November 2013
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 168
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Genetic mapping; Plant; Fitness; Defense
Date Deposited: 31 Jan 2014 20:29
Last Modified: 08 Mar 2019 22:23


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