Physiological and Metabolic Responses of Thellungiella salsuginea to Osmotic Stress

Abstract

<p> Abiotic stresses such as extreme temperatures, drought and high salinity severely compromise plant productivity, and have placed selective pressure for the acquisition of traits enabling plants to adjust to and recover from these unfavorable environmental conditions. Thellungiella salsuginea is a plant that is native to highly saline and semiarid environments and exhibits an exceptional ability to tolerate abiotic stress. In this thesis, I report on laboratory and field studies aimed at identifying traits that allow Thellungiella to tolerate harsh environmental conditions. It was found that Thellungiella accumulates organic solutes in response to abiotic stress. Transcript and metabolite profiling approaches were used to identify metabolic pathways important for the accumulation of compatible organic solutes in Thellungiella in response to sub-optimal environmental conditions. The relative abundance of transcripts encoding enzymes associated with the biosynthesis of compatible organic solutes such as proline or galactinol showed stress-responsive increases in cabinet-grown material and these metabolites were accumulated in salt or drought treated plants, respectively. However, proline and galactinol were found to be of low relative abundance in leaves of field plants. In contrast, several carbohydrates including sucrose, glucose, and fructose made a greater relative contribution to the field plant profiles suggesting that carbohydrates play an important role in plant abiotic stress tolerance during growth under field conditions. The identification of stress-specific metabolic changes can be used to identify important biochemical traits underlying environmental stress tolerance in Thellungiella. This information can be used to improve the tolerance of stress -sensitive crops (including a related crucifer species, canola) that are grown in areas where persistent droughts, saline soils and early or late frosts frequently occur. </p>