Browsing by Author "Nxele, Xolisa"

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    A biochemical and proteomic analysis of sugargraze sorghum under hyperosmotic stress
    (University of the Western Cape, 2015) Nxele, Xolisa; Ndimba, Bongani K.; Klein, Ashwil
    Sugargraze is a moderately drought tolerant sweet sorghum hybrid which is ideal for grazing, winter stand over and pit silage. A major advantage that Sugargraze has over other forages is its very high sugar content which improves feed quality thus increasing palatability and results in significantly reduced feed wastage. This study explored the influence of hyperosmotic stress on plant development, ROS accumulation, antioxidant capacity and the extent of cell death. Heat shock protein (Hsp70) expression immunoblotting assays were used to demonstrate whether the various treatment conditions induced stress within natural physiological parameters for the experimental material. This was coupled with the separation, visualization and identification of abundant proteins in Sugargraze leaves in response to hyperosmotic stress using two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry (MS). The results showed that hyperosmotic stress significantly influences plant development by reducing plant biomass and increasing the levels of ROS accumulation, proline content and subsequently reducing total chlorophyll content. An over accumulation of ROS in the form of hydrogen peroxide and lipid peroxidation was observed in the stressed plants which was supported by the extent of cell death. Although an increase in antioxidant enzyme activity (in the form of total enzymatic activity or individual isoform activity) in response to hyperosmotic stress was observed, this increase was not sufficient to counter the deleterious effects caused by the stress conditions hence the decrease in plant biomass and increase in cell death. Western blotting analysis of Sugargraze leaf tissues using Hsp70 antibodies showed that hyperosmotic stress induced Hsp70 expression to levels significantly higher than observed for the control plants. A total of thirteen CBB stained spots were selected for mass spectrometric identification, owing to their good resolution and abundance levels, and of these, nine were positively identified. Identified proteins were divided into functional categories including both known and novel/putative stress responsive proteins. Molecular and physiological functions of some of the proteins of interest identified will be subjected to further investigation via bioinformatic and molecular biology approaches.
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    Drought and salinity stress alters ROS accumulation, water retention, and osmolyte content in sorghum plants
    (Elsevier, 2017) Nxele, Xolisa; Klein, Ashwil; Ndimba, Bongani Kaiser
    biotic stresses such as drought and salinity are major environmental factors that influence crop productivity worldwide. These adverse conditions induce osmotic stresses in plant cells by decreasing water availability, thus leading to loss of cell turgor and the accumulation of reactive oxygen species (ROS) that are detrimental to plant growth and development. To survive such harsh environmental conditions, plants must initiate intracel- lular and physiological signaling networks to rapidly respond and efficiently neutralize these stresses. Inefficient scavenging of ROS would lead to increased levels of cell death, thus inhibiting plant growth and reducing crop productivity. This study investigates the effect of drought and salinity stress on plant growth, water retention, oxidative damage, chlorophyll content, and proline accumulation in sorghum plants. Plant growth, biomass, and leaf chlorophyll were significantly reduced whereas the total proline content was enhanced in response to stress conditions. The significant increase in hydrogen peroxide content as a consequence of stress conditions resulted in augmented levels of lipid peroxidation, which was manifested as extensive cell death and biomass reduction.
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    Identification of sub-clinical biomarkers that predict the risk of developing diabetic cardiomyopathy
    (University of the Western Cape, 2022) Nxele, Xolisa; Benjeddou, Mongi
    Cardiovascular disease (CVD) is the leading cause of death of people with obesity and type 2 diabetes (T2DM). According to a statistical report from the World Health Organization (WHO), approximately 17.9 million people die annually because of CVD and diabetic cardiomyopathy (DCM), a disease of the heart muscle occurring in the absence of coronary artery disease or hypertension. Although not fully elucidated, the pathophysiology of DCM includes myocardial left ventricular hypertrophy, impaired calcium handling, energy metabolism, inflammation, apoptosis and myocardial fibrosis.