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Exploring Candidate Genes for the `S-locus': The Control of Heterostyly Across Wild and Cultivated Species in the Genus Linum

DESMOND, ELEANOR,LAUREN (2018) Exploring Candidate Genes for the `S-locus': The Control of Heterostyly Across Wild and Cultivated Species in the Genus Linum. Masters thesis, Durham University.

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Heterostyly in \textit{Linum }is characterised by the presence of two floral morphs with their male and female reproductive organs located at different heights. It is an adaptation designed to encourage cross-pollination and minimise self-fertilisation. In \textit{Primula}, heterostyly is controlled by two alleles present at a single locus, designated the \textit{`S-locus'}. The identities of genes responsible for controlling heterostyly in \textit{Linum} remain to be determined. Although \textit{Primula} and \textit{Linum} are evolutionarily distant, the recent elucidation of a 278 kb \nomenclature{kb}{Kilobase} region conforming to the \textit{S-locus} in \textit{Primula vulgaris} has provided a guide for potential candidate genes.

A series of candidate genes, including \textit{GLO\textsuperscript{T}} and \textit{CYP\textsuperscript{T}} have been identified from other heterostylous species. RNA-Sequencing analysis has been employed to assess the expression of candidate genes in 44 floral tissue samples, across 10 \textit{Linum} species. Sequence reads were mapped to a reference \textit{Linum tenue} assembly and read data was used to perform morph-specific differential expression analysis between the two heterostylous morphs and between heterostyles and homostyles. Relative expression of candidate genes was validated by qPCR analysis on both long and short-styled morphs of \textit{L. tenue} at various stages of floral growth. It was anticipated that \textit{S-locus} genes found in \textit{Primula} and others would have orthologues in \textit{Linum} and that there would be expression of candidate genes in the 'thrum morph', but not the 'pin morph'. It was also expected that the candidate genes would show differential expression during different stages of floral development.

There was no clear evidence of differential expression of any tested candidate gene between the two floral morphs or between the three different developmental stages, neither was there an observed difference in candidate gene expression between heterostylous and homostylous individuals. The most differentially expressed genes were found to be related to stress-response functions. Differences were observed in the relative expression of GLOT and CYPT between the qPCR and RNA-Seq methods of differential expression analysis. It thus could not be substantiated that heterostyly behaves in the same way in Linum as in Primula.

Item Type:Thesis (Masters)
Award:Master of Science
Keywords:Heterostyly, Linum, S-locus, qPCR, RNA-Seq, Differential Expression Analysis
Faculty and Department:Faculty of Science > Biological and Biomedical Sciences, School of
Thesis Date:2018
Copyright:Copyright of this thesis is held by the author
Deposited On:13 Dec 2018 12:20

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