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UBC Theses and Dissertations

Molecular characterization of the black yeast Hortaea werneckii in saline environments Formby, Sean Philip


As of 2007, over 30 million hectares are affected by salinization resulting in poor crop yield and a reduction of food production. Reversing salinization of soil is an expensive and long term process. The bioengineering of plants to better cope with salinization of the soil is an ongoing research effort. Hortaea werneckii is an extremely halotolerant (salt tolerant) black yeast and can grow in the absence of salt or in almost saturating conditions (5M NaCl). Its natural ecological niche is the solar salterns of Slovenia which have range of environmental extremities such as the salt concentration, low oxygen, and high UV intensity. Recently it was discovered that this yeast has had recent genome duplication and 90% of the proteins exist in duplicate. The whole genome duplication and the extreme NaCl tolerance of H. werneckii provide an interesting model to investigate molecular mechanisms involved in salt stress. In this study, H. werneckii’s genome assembly is improved (increased contiguity) and used for subsequent molecular experiments such as MNase-seq and RNA-seq. These experiments were used to examine differences of gene expression and the corresponding chromatin architecture across a range of saline conditions to determine important molecular mechanism in salt tolerance. H. werneckii increases respiration in response to salt stress exemplified by the upregulation of mitochondrial associated genes and antioxidant defense genes. Additionally, H. werneckii genes encoding zinc transporters and genes involved in glycerol assimilation were increased in response to high salt. The chromatin landscape of some of these genes differs from other yeasts such as S. cerevisiae. Using next generation sequencing and third generation sequencing a more complete picture of H. werneckii’s mechanisms of salt tolerance has been obtained while also creating an extensive data-base for future research.

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