Date of Award

2017

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Forest Molecular Genetics and Biotechnology (MS)

Administrative Home Department

College of Forest Resources and Environmental Science

Advisor 1

Victor Busov

Committee Member 1

Molly Cavaleri

Committee Member 2

Hairong Wei

Abstract

The Full-length complementary DNA OvereXpression (FOX) system is an approach to generating gain-of-function (GF) plants predominantly used for studying Arabidopsis. This approach inserts T-DNAs containing random full-length complementary DNA (fl-cDNA) with upstream promoter and downstream terminator into the host plant genome. Studies using this method report the success generating overexpression populations with high mutation rates. We choose to investigate the feasibility and effectiveness of this method using poplars. We suspected using a succulent xylem specific fl-cDNAs library would enrich the transformant poplars with mutants affected in traits specific to woody tissue development. We observed a characteristically high mutation rate (17.7%) significantly enriched for mutants with altered cell wall composition. We determined selection of tissues for RNA sampling greatly influence types of genes inserted and phenotypes observed, as seen by the enrichment for FOX mutants affected in traits liked to developing xylem. Furthermore, using the FOX system we discovered overexpression of a fl-cDNA homologous for poplar specific LONELY GUY 1 (LOG1) resulted in a near doubling of stem xylem width. LOG1 belongs to a gene family encoding enzymes that directly convert inactive cytokinins to their active conformations. Examining stem sections, we determined LOG1 overexpression greatly increased active cytokinin concentration causing xylem proliferation. Complete phenotype recapitulation for LOG1 FOX line using Gateway OE method validated the feasibility of the FOX system for studying poplars.

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