Soil salinity is a major abiotic stress for land plants, and multiple mechanisms of salt tolerance have evolved. Tissue tolerance is one of these mechanisms, which involves the sequestration of sodium into the vacuole to retain low cytosolic sodium
concentrations. This enables the plant to maintain cellular functions, and ultimately maintain growth and yield. However, the molecular components involved in tissue tolerance remain elusive. Several candidate genes for vacuolar sodium sequestration have recently been identified by proteome analysis of vacuolar membranes purified from the salt-tolerant cereal Hordeum vulgare (barley). In this study, I aimed to characterize these candidates in more detail. I successfully cloned coding sequences for the majority of candidate genes with primers designed based on the barley reference genome sequence. During the course of this study a newer genome sequence with improved annotations was published, to which I also compared my observations.
To study the candidate genes, I used the heterologous expression system Saccharomyces cerevisiae (yeast). I used several salt sensitive yeast strains (deficient in intrinsic sodium transporters) to test whether the candidate genes would affect
their salt tolerance by mediating the sequestration of sodium into the yeast vacuole. I observed a reduction in growth upon expression for several of the gene candidate under salt-stress conditions. However, confocal microscopy suggests that most gene
products are subject to degradation, and did not localize to the vacuolar membrane (tonoplast). Therefore, growth effects cannot be linked to protein function without further evidence.
Various potential causes are discussed, including inaccuracies in the genome resource used as reference for primer design and issues inherent to the model system. Finally, I make suggestions on how to proceed to further characterize the candidate genes and hopefully identify novel sodium transporters from barley.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/623420 |
| Date | 05 1900 |
| Creators | Scheu, Arne Hagen August |
| Contributors | Tester, Mark A., Biological and Environmental Science and Engineering (BESE) Division, Pain, Arnab, Mahfouz, Magdy M. |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | 2023-05-23, At the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis will become available to the public after the expiration of the embargo on 2023-05-23. |
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