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Degree

Doctor of Philosophy, Case Western Reserve University, Biology, 2011.

Abstract

Flax (Linum usitatissimum L.) undergoes heritable genomic changes in response to nutrient stress, including changes in total DNA content, rDNA copy number variation, and the insertion of Linum Insertion Sequence 1 (LIS-1). LIS-1 represents a novel type of insertion sequence, as it appears to be assembled from sequences dispersed throughout the flax genome before its insertion into a defined target sequence. To begin to find genes and genomic regions controlling the stress response, a genetic map of the flax genome was created using crosses between responsive and unresponsive lines of flax. Simple sequence repeats (SSRs) were isolated from the flax genome and markers that were polymorphic between the flax lines were used to create a preliminary genetic map, which contained 37 markers in 17 linkage groups. The responsiveness of the F2 offspring of reciprocal crosses between Stormont Cirrus, a responsive line, and Bethune, an unresponsive line, was determined. The appearance of LIS-1 was assayed using PCR on DNAs isolated from F2s grown under nutrient stress conditions at two time points. Changes in large and small rDNA copy number were also measured using quantitative PCR (qPCR). The number of loci involved in responsiveness was determined for each measure of responsiveness at each time point. Changes in rDNA copy number was determined to be the first step in the stress response, with 1-2 dominant loci controlling changes in the copy number of genes for large and small rDNA. The early insertion of LIS-1 appears to require 3-4 dominant loci, while a later response is controlled by 2 independent, dominant loci. The early LIS-1 response is linked to marker 258, while the late LIS-1 response is linked to marker JA23 and to the loci for the rDNA response. Marker 157-158 was linked to the rDNA response in the 5S genes. These markers indicate genomic regions in which the genes that control responsiveness reside, which can be analyzed in greater detail to identify specific genes controlling the response to nutrient stress in flax.

Subject Headings

Biology; Genetics; Molecular Biology; Plant Biology

Keywords

flax; Linum usitatissimum; genetic mapping; stress response; LIS-1

Committee / Advisors

Christopher Cullis, PhD (Advisor)
David Burke, PhD (Committee Member)
Barbara Kuemerle, PhD (Committee Member)
Saba Valadkhan, PhD (Committee Member)

Pages

178p.

Document number: case1301676557
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=case1301676557

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