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Type: Theses
Title: Root cell-type specific expression of multiple salinity tolerance genes to alter plant shoot sodium accumulation
Author: Wellman, Gordon Bertram
Issue Date: 2016
School/Discipline: School of Agriculture, Food and Wine
Abstract: Increasing soil salinity of agricultural land is of growing concern world-wide as excessive soil salinity has a detrimental effect on growth and yield of many plant species of agricultural importance. The accumulation of sodium ions (Na⁺) from saline soils into the shoots of crop plants contributes to the negative effect salinity has on plant growth in cereals. In recent years, many molecular targets involved in Na⁺ transport in plants have been identified in a number of species. Genetic modification (GM) utilising these genes may enable manipulation of Na⁺ transport with an aim of reducing Na⁺ accumulation in the shoot. Constitutive and/or tissue-specific over-expression (OX) of such genes in transgenic plants can prove beneficial in reducing Na⁺ shoot accumulation and improve plant salinity tolerance in some cases. However, further reductions could be made by fine tuning Na⁺ transport through the plant by co-expressing multiple salinity tolerance associated genes of interest (GOI) in specific root-cell types. To date, this has proved difficult. Previously generated barley (Hordeum vulgare c.v Golden Promise) lines with putative cell-type specific OX of salinity tolerance associated GOIs, High Affinity K⁺-Transporter 1;5 (HvHKT1;5) and vacuolar H⁺-pyrophosphatase 1 (HvHVP1), were screened in saline hydroponics to assess for improvements in salinity tolerance. Lines with the simultaneous root-cell-type specific OX of both HvHKT1;5 and HvHVP1 were developed through hybridisation and assessed for improved salinity tolerance. Although no significant improvements were identified in both the single- or dual-GOI transgenic lines, this approach could be used for other transgenic lines with cell-type specific OX of other GOIs combinations. The role of vacuolar H⁺-pyrophosphatase 1 (AtAVP1) was re-examined when over-expressed in the root-epidermal and –cortical cell types in the model plant species Arabidopsis thaliana. OX of AtAVP1 in these cell-types was thought to improve Na⁺ sequestration and there-by improve salinity tolerance. However, saline hydroponics assays of lines with root-epidermal and/or –cortical OX of AtAVP1 failed to identify improvements in plant salt tolerance or Na⁺ uptake, suggesting that AtAVP1 contributes little to Na⁺ sequestration in these cell-types. Finally, a system that would allow the cell-type specific over-expression of different GOIs in different root cell-types was developed. Such a system would allow the trialling different gene combinations to identify combinations that would allow more targeted manipulation of Na⁺ transport throughout a plant and alter salinity tolerance. This work was carried out in the model plant species, Arabidopsis thaliana, and cell-type expression was enabled through the use of dual GAL4 and HAP1 enhancer-trap systems and trans-activation constructs. Lines and constructs were developed to allow the cell-type specific OX of selected GOIs, however testing of dual salinity tolerance GOI lines was not achievable during the timeframe of this project.
Advisor: Jacobs, Andrew Keith
Roy, Stuart John
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2016.
Keywords: salt
soil salinity
genetic modification
cell-type specific expression
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
DOI: 10.4225/55/5af50a34c94fe
Appears in Collections:Research Theses

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