UWCScholar :: Browsing by Author "Keyster, Marshall"

Browsing by Author "Keyster, Marshall"

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3,3' Diindolylmethane mediated signalling and its role in Brassica napus L. responses to vanadium
(University of the Western Cape, 2016) Gokul, Arun; Keyster, Marshall
Anthropogenic activities such as mineral mining, improper watering practices, and the use of heavy metal contaminated fertilizers have caused an influx of heavy metals into arable lands. These heavy metals may have a negative impact on plant growth, as they are able to increase ROS species within plants resulting in plant metabolism deterioration and tissue damage. Heavy metals also have the ability to render important enzymes non-functional or may decrease their activity resulting in poor growth. Vanadium was used as the heavy metal of choice in this study, as South Africa is one of the top producers of this metal worldwide. In an effort to improve growth of crop plants, mechanisms have to be identified to increase growth under vanadium stress. One method to increase growth is the use of exogenously applied signalling molecules. In this study, one such compound 3,3' Diindolylmethane (DIM) was investigated to identify whether it had growth promoting properties.
3,3'-diindolylmethane improves drought tolerance of Zea mays through enhancing antioxidant activity
(University of the Western Cape, 2018) Basson, Gerhard Leroy; Ludidi, Ndiko; Keyster, Marshall; Gokul, Arun
Maize is one of the most abundantly produced cereals and contributes to about 40% of the global cereal production. This figure will have to increase in order to feed the ever-growing human population. One of the major environmental constraints that impact maize production is drought. Plants use antioxidant defences to cope with drought stress. Understanding and improving these defence mechanisms will be important to improve overall drought tolerance. A previous study done by Gokul and authors in 2016 showed that 3,3’-diindolylmethane (DIM) improves both seed germination and seedling shoot growth in Brassica napus. Plants belonging to the Brassicaceae family have the metabolic machinery to synthesize glucosinolates such as DIM, which play vital roles in physiological and stress responses. These responses have not been investigated in plants such as maize, which lack the machinery to produce DIM. Therefore, this study investigated the effects of exogenously applied DIM on the physiological and biochemical responses of maize under drought stress. Physiological parameters such as relative water content, chlorophyll content and lipid peroxidation, were determined in order to understand how drought and DIM , as separate or combined treatments, affected the plants. Additionally, proline accumulation was also assessed because free proline plays a role as an osmoprotectant during stress. The accumulation of ROS, namely hydrogen peroxide, was measured using spectrophotometric assays to determine how the above treatments affect ROS accumulation in maize. As a result of changes in the ROS content in due to the treatments, it would only be natural to investigate the changes in antioxidants as well. Given that hydrogen peroxide was the ROS to be measured, we therefore investigated the antioxidant enzymatic activities responsible for hydrogen peroxide scavenging. Therefore, changes in Ascorbate peroxidase (APX) and catalase (CAT) were assessed. An improved drought response was observed in maize plants treated with DIM as these plants had better ability to maintain their water status than when no DIM was applied. This is indicated by water-deprived plants treated with DIM having a higher RWC than water-deprived plant without DIM.
Analytical studies of antimicrobial peptides as diagnostic biomarkers for the detection of bacterial and viral Pneumonia
(MDPI, 2022) Bakare, Olalekan Olanrewaju; Gokul, Arun; Keyster, Marshall
Pneumonia remains one of the leading causes of infectious mortality and significant economic losses among our growing population. The lack of specific biomarkers for correct and timely diagnosis to detect patients’ status is a bane towards initiating a proper treatment plan for the disease; thus, current biomarkers cannot distinguish between pneumonia and other associated conditions such as atherosclerotic plaques and human immunodeficiency virus (HIV). Antimicrobial peptides (AMPs) are potential candidates for detecting numerous illnesses due to their compensatory roles as theranostic molecules. This research sought to generate specific data for parental AMPs to identify viral and bacterial pneumonia pathogens using in silico technology.
Biomedical Relevance of Novel Anticancer Peptides in the Sensitive Treatment of Cancer
(MDPI, 2021) Bakare, Olalekan; Gokul, Arun; Keyster, Marshall
The global increase in cancer mortality and economic losses necessitates the cautious quest for therapeutic agents with compensatory advantages over conventional therapies. Anticancer peptides (ACPs) are a subset of host defense peptides, also known as antimicrobial peptides, which have emerged as therapeutic and diagnostic candidates due to several compensatory advantages over the non-specificity of the current treatment regimens. This review aimed to highlight the ravaging incidence of cancer, the use of ACPs in cancer treatment with their mechanisms, ACP discovery and delivery methods, and the limitations for their use. This would create awareness for identifying more ACPs with better specificity, accuracy and sensitivity towards the disease. It would also promote their efficacious utilization in biotechnology, medical sciences and molecular biology to ease the severity of the disease and enable the patients living with these conditions to develop an accommodating lifestyle.
Building HMM and molecular docking analysis for the sensitive detection of anti-viral pneumonia antimicrobial peptides (AMPs)
(Nature Research, 2021) Bakare, Olalekan Olanrewaju; Keyster, Marshall; Pretorius, Ashley
Pneumonia is the main reason for mortality among children under five years, causing 1.6 million deaths every year; late research has exhibited that mortality is increasing in the elderly. A few biomarkers used for its diagnosis need specificity and precision, as they are related to different infections, for example, pulmonary tuberculosis and Human Immunodeficiency Virus. There is a quest for new biomarkers worldwide to diagnose the disease to defeat these previously mentioned constraints. Antimicrobial peptides (AMPs) are promising indicative specialists against infection. This research work used AMPs as biomarkers to detect viral pneumonia pathogens, for example, Respiratory syncytial virus, Influenza A and B viruses utilizing in silico technologies, such as Hidden Markov Model (HMMER). HMMER was used to distinguish putative anti-viral pneumonia AMPs against the recognized receptor proteins of Respiratory syncytial virus, Influenza A, and B viruses. The physicochemical parameters of these putative AMPs were analyzed, and their 3-D structures were determined utilizing I-TASSER. Molecular docking interaction of these AMPs against the recognized viral pneumonia proteins was carried out using the PATCHDOCK and HDock servers. The results demonstrated 27 anti-viral AMPs ranked based on their E values with significant physicochemical parameters in similarity with known experimentally approved AMPs. The AMPs additionally had a high anticipated binding potential to the pneumonia receptors of these microorganisms sensitively. The tendency of the putative anti-viral AMPs to bind pneumonia proteins showed that they would be promising applicant biomarkers to identify these viral microorganisms in the point-of-care (POC) pneumonia diagnostics. The high precision observed for the AMPs legitimizes HMM’s utilization in the disease diagnostics’ discovery process
Capacity to control oxidative stress-induced caspase-like activity determines the level of tolerance to salt stress in two contrasting maize genotypes
(Springer, 2013) Keyster, Marshall; Klein, Ashwil; Du Plessis, Morné; Jacobs, Alex; Kappo, Abidemi; Kocsy, Gábor; Galiba, Gábor; Ludidi, Ndiko
The response of two maize (Zea mays L.) genotypes, named GR (salt-tolerant) and SK (salt-sensitive), to salt stress (150 mM NaCl) was investigated under controlled environmental growth conditions. Genotype SK experienced more oxidative damage than the GR genotype when subjected to salt stress, which corresponded to higher O2- production rate and H2O2 content in the SK genotype than the GR genotype. Induction of caspase-like activity in response to salt stress was stronger in the SK genotype than in the GR genotype. On the other hand, induction of antioxidant enzyme activity to scavenge O2- and H2O2 in response to salt stress was weaker in the SK genotype than in the GR genotype. Consequently, the higher level of oxidative damage in the SK genotype in response to salt stress was manifested as more extensive cell death and biomass reduction in the SK genotype than it was in the GR genotype. Our results suggest that a direct relationship exists between salt stress-induced oxidative damage and cell death-inducing caspase-like activity, with tolerance to the salt stress being controlled by the efficiency of the plantantioxidant enzymes in limiting salt stress-induced oxidative damage and thus limiting cell death-inducing caspase-like activity.
Characterisation of a novel soybean candidate glutathione peroxidase/thioredoxin-dependent peroxidase in soybean exposed to osmotic/drought stress
(University of the Western Cape, 2012) Phillips, Kyle; Ludidi, Ndiko; Keyster, Marshall
Drought stress is a major contributor to reduced soybean crop yield and quality, this can however be mitigated by the plant’s antioxidant defence mechanisms. One group of antioxidant enzymes that are active in these defence mechanisms are glutathione peroxidases (GPXs). GPXs are antioxidant proteins which are able to reduce H2O2, a toxic reactive oxygen species which accumulates under stress conditions. This study aims at isolating the protein encoded by Glyma01g42840 and determining if it has Phospholipid hydroperoxidase glutathione peroxidase (PHGPX) and/or Thioredoxin dependent peroxidase (TRX-PX) activity as well as assaying the effect of Drought stress on the expression of this putative GPX . This will be accomplished by molecular cloning, sequencing as well as the expression of the isolated protein to assay it enzymatic activity. It was found that the enzyme encoded by Glyma01g42840 is able to use glutathione and thioredoxin as electron donors for the detoxification peroxides, however enzymatic activity is more efficient when using glutathione as an electron donor. In conclusion it was found that glyma01g42840 encodes an enzyme which is able to utilise more than one electron donor and as glutathione produces the greatest amount of enzymatic activity it can be said that glyma01g42840 encodes a GPX.
Characterization of a novel soybean candidate glutathione peroxidase/thioredoxin-dependent peroxidase under salt stress
(2012) Adams, Ruqaiyah; Ludidi, N. N.; Keyster, Marshall
The production of reactive oxygen species (ROS) is prominent in all aerobic metabolisms including plants. For this reason, the redox homeostasis of the production and scavenging of these intermediates is imperative for growth, development and survival during unfavourable conditions. In this study, a putative glutathione peroxidase gene (Glyma17g34110) from Glycine max (soybean) was identified and analyzed. The successful characterisation of Glyma17g34110 provided evidence of it being a glutathione peroxidase using glutathione as its preferred electron donor and substrate. Furthermore, it is known that antioxidant enzymes such as GPX exist in various tissues, performing a diverse set of functions. By a bioinformatic analysis of Glyma17g34110 and its promoter region, it was indicated that Glyma17g34110 could be a putative chloroplast protein that could play an important role in photosynthesis.One of the major factors affecting plant growth and development worldwide is abiotic stresses such as salinity. In the presence of salinity the production of harmful ROS is increased, resulting in detrimental reactions with important biological features (DNA, protein and lipid membranes), leading to cell death. The analysis of Glyma17g34110 under salt stress revealed that it is a salt sensitive gene and thus, the down-regulation of Glyma17g34110 could be due to the lack of known defence and response cis-acting elements present in the promoter region. Furthermore, it was proven in previous studies that the application of exogenous nitric oxide (NO) increases the activity of antioxidant enzymes. In this thesis it was observed that the presence of exogenously applied NO increased the expression of Glyma17g34110 tremendously in all soybean tissues (leaves, roots and nodules) investigated.Studies have found numerous cis-acting elements to be NO responsive, however, none of these elements were found in the promoter region upstream of glyma17g34110. This suggests that novel cis-acting elements could be present in the promoter region of Glyma17g34110.Thus, increasing the expression of Glyma17g34110 during salinity in the presence of NO, as well as the identification of these novel cis-acting elements, could lead to the enhancement of the defence mechanisms against ROS, which could lead to increasing plant tolerance to stress.
Comparative analysis of 3, 3'- diindolylmethane and indole-3-carbinol respective treatments in Brassica napus L.
(University of the Western Cape, 2017) Carelse, Mogamat Fahiem; Keyster, Marshall
Lately, there has been serious contamination of soils and ground water caused by mineral mining and environmental pollution leading to heavy metal accumulation within soils and over time rendering the soil infertile. The contaminated soil affects crop; yield, germination percentage and leads to seed dormancy. Additionally, as plants are sessile organisms, exposure to environmental stress involves different defense cycles and signalling molecules. Oxidative stress, increases the production of reactive oxygen species (ROS) at greater rates than that of the metabolism. Moreover, oxidative damage leads to the loss in cellular function and eventually death. Nonetheless, plants have adapted ROS-scavenging systems driven by reduction-oxidation reactions as defense mechanisms. In this way, cellular homeostasis is an essential defending process and finding means to optimize these reactions would benefit in the development of plants. Hence, environmentally friendly solutions are being reported such as using glucosinolates, a secondary plant metabolite found in relatively high concentrations within crucifers such as Brassica napus L.
Decoding heavy metal stress signalling in plants: Towards improved food security and safety
(MDPI, 2020) Keyster, Marshall; Niekerk, Lee Ann; Basson, Gerhard
The mining of heavy metals from the environment leads to an increase in soil pollution, leading to the uptake of heavy metals into plant tissue. The build-up of toxic metals in plant cells often leads to cellular damage and senescence. Therefore, it is of utmost importance to produce plants with improved tolerance to heavy metals for food security, as well as to limit heavy metal uptake for improved food safety purposes. To achieve this goal, our understanding of the signaling mechanisms which regulate toxic heavy metal uptake and tolerance in plants requires extensive improvement. In this review, we summarize recent literature and data on heavy metal toxicity (oral reference doses) and the impact of the metals on food safety and food security. Furthermore, we discuss some of the key events (reception, transduction, and response) in the heavy metal signaling cascades in the cell wall, plasma membrane, and cytoplasm. Our future perspectives provide an outlook of the exciting advances that will shape the plant heavy metal signaling field in the near future.
Effects of exogenous myristic acid on growth and germination of Brassica napus L. under zirconium toxicity
(University of the Western Cape, 2016) Addinall, Riyaad; Keyster, Marshall
Lipids when exogenously applied are known to cause various changes in ROS levels produced within plants. They can either be beneficial to the plant when not stimulating the overproduction of ROS thus resulting in improved germination and development or on the contrary, increasing the level of ROS produced, causing oxidative stress and thus leading to cell death of the plant. In this study, we report that a saturated fatty acid known as MA increased the germination percentages of Brassica napus L. seedlings when applied at a low concentration. When applied at higher concentrations, it was shown that elevated levels of ROS within the seedlings occurred therefore leading to a decrease in germination percentage as well as stunting of seedling growth. Physiological experiments such as biomass and cell death determination were conducted to further elucidate the effects of MA on the seedlings. Biochemical assays were performed to determine the oxidative state of specific ROS such as superoxide (O2-) and hydrogen peroxide (H2O2).
Efficient superoxide scavenging and metal immobilization in roots determines the level of tolerance to vanadium stress in two contrasting Brassica napus genotypes
(Elsevier, 2018) Gokul, Arun; Cyster, Lilburne F.; Keyster, Marshall
Brassica napus also known as Rapeseed is a member of the Brassicaceae family which is mainly cultivated for its oil-rich seeds. Indeed, B. napus is ranked the third-largest source of vegetable oil in the world. Brassica napus growth, development and yield are negatively affected by heavy metals. Vanadium is a heavy metal and presence in high concentrations impact plant growth and development negatively. However, the impact of Vanadium on B. napus growth and development is unknown. Therefore, in this study we assessed the effects of Vanadium stress on leaf physiology and biochemistry response of two B. napus cultivars (namely Agamax and AV Garnet). A randomised pot-experiment under controlled conditions was used to grow B. napus cultivars under control (dis- tilled water) and Vanadium (350 μM NaVO3) treatments. Results showed that Vanadium caused yellowing of AV Garnet leaves but not Agamax leaves. Furthermore, Vanadium stress caused a more severe decrease in leaf dry and fresh weight of AV Garnet as compared to the decrease in leaf dry and fresh weight of Agamax.
Exogenous p-coumaric acid improves salvia hispanica l. Seedling shoot growth
(MDPI Open Access Journals, 2019) Nkomo, Mbukeni; Gokul, Arun; Keyster, Marshall; Klein, Ashwil
p-Coumaric acid (p-CA) belongs to a family of natural esters of hydroxycinnamic acid compounds that have been shown to modulate plant growth and metabolism. In this study, we investigated the effect of exogenous p-CA on plant growth, reactive oxygen species (ROS)-induced oxidative damage, photosynthetic metabolism, osmolyte content and changes in superoxide dismutase (SOD) enzymatic activity.
Farmers’ Knowledge, Perceptions and Attitudes on Crop-Dairy Goat Integration Farming System in Elgeyo Marakwet County
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Keyster, Marshall; Cheboi, Juliana; Greathead, Henry
Several interventions have been promoted in dry areas to improve food and nutrition insecurity. However, studies on the key drivers influencing adoption and uptake are limited. Therefore, research was undertaken to investigate farmers’ knowledge, perceptions and attitudes on an integrated crop–dairy goat farming system in Elgeyo Marakwet. A cross-sectional study entailing a household survey of 201 respondents, six key informant interviews and eight focus group discussions was undertaken. This study utilized a multi-stage sampling procedure to sample the farmers and calculated the sample size using Krejcie and Morgan tables. Quantitative data were subjected to descriptive and inferential statistics using SPSS software version 22, while qualitative data were analysed using N-vivo software version 10 through the Framework Analysis method. The findings show that drought (84.6%), change in rainfall pattern (77.6%), farm size (57.2%), unavailability of quality seeds (52.2%), fodder acreage (58.7%), diseases (69.7%) and pest severity (68.7%) are the principal drivers for adoption of the integrated crop–dairy goat farming system. Dairy goats are associated with women in this community since they are regarded as small animals and have no monetary value, hence increasing the participation of women in the access, control and decision making of agricultural resources. To increase adoption, strategies focusing on improving water supply, quality seeds, agro-veterinary services and production are advocated.
Gallic acid modulates salt stress tolerance in soybean plants by regulating antioxidant capacity
(University of the Western Cape, 2017) Menzi, Pateka; Klein, Ashwil; Keyster, Marshall
Soybean [Glycine max L (mer)] is one of the top commodity crops in the world including South Africa (de Beer and Prinsloo, 2013). These small yet important podded legumes are a great source of protein and are used in many forms.
Heavy metal stress and mitogen activated kinase transcription factors in plants: Exploring heavy metal-ros influences on plant signalling pathways
(John Wiley and Sons Inc, 2024) Niekerk, Lee-Ann; Basson, Gerhard; Klein, Ashwil; Keyster, Marshall
Due to their stationary nature, plants are exposed to a diverse range of biotic and abiotic stresses, of which heavy metal (HM) stress poses one of the most detrimental abiotic stresses, targeting diverse plant processes. HMs instigate the overproduction of reactive oxygen species (ROS), and to mitigate the adverse effects of ROS, plants induce multiple defence mechanisms. Besides the negative implications of overproduction of ROS, these molecules play a multitude of signalling roles in plants, acting as a central player in the complex signalling network of cells. One of the ROS-associated signalling mechanisms is the mitogen-activated protein kinase (MAPK) cascade, a signalling pathway which transduces extracellular stimuli into intracellular responses. Plant MAPKs have been implicated in signalling involved in stress response, phytohormone regulation, and cell cycle cues. However, the influence of various HMs on MAPK activation has not been well documented. In this review, we address and summarise several aspects related to various HM-induced ROS signalling. Additionally, we touch on how these signals activate the MAPK cascade and the downstream transcription factors that influence plant responses to HMs. Moreover, we propose a workflow that could characterise genes associated with MAPKs and their roles during plant HM stress responses.
Identification and characterisation of potential virulence genes of Salmonella from rooibos tea
(University of the Western Cape, 2015) Johannes, Nashleen Shereen; Keyster, Marshall; Gouws, Pieter
The aim of this study was to investigate the presence of Salmonella in the tea processing environment, to identify and detect potential virulence genes isolated from Salmonella in the tea, and to determine the antibiotic resistance levels of Salmonella isolated from fermented Rooibos.
Identification and Molecular validation of Biomarkers for the accurate and sensitive diagnosis of bacterial and viral Pneumonia
(University of Western Cape, 2019) Bakare, Olalekan Olanrewaju; Pretorius, Ashley; Keyster, Marshall
Pneumonia remains the major cause of death in children and the elderly and several efforts have been intensified to reduce the rate of pneumonia infection. The major breakthrough has been the discovery of certain biomarkers for the diagnosis of pneumonia through immunogenic techniques.
Identification of biomarkers for the accurate and sensitive diagnosis of three bacterial pneumonia pathogens using in silico approaches
(Springer Nature, 2020) Bakare, Olalekan Olanrewaju; Keyster, Marshall; Pretorius, Ashley
: Pneumonia ranks as one of the main infectious sources of mortality among kids under 5 years of age, killing 2500 a day; late research has additionally demonstrated that mortality is higher in the elderly. A few biomarkers, which up to this point have been distinguished for its determination lack specificity, as these biomarkers fail to build up a differentiation between pneumonia and other related diseases, for example, pulmonary tuberculosis and Human Immunodeficiency Infection (HIV). There is an inclusive global consensus of an improved comprehension of the utilization of new biomarkers, which are delivered in light of pneumonia infection for precision identification to defeat these previously mentioned constraints. Antimicrobial peptides (AMPs) have been demonstrated to be promising remedial specialists against numerous illnesses. This research work sought to identify AMPs as biomarkers for three bacterial pneumonia pathogens such as Streptococcus pneumoniae, Klebsiella pneumoniae, Acinetobacter baumannii using in silico technology. Hidden Markov Models (HMMER) was used to identify putative anti-bacterial pneumonia AMPs against the identified receptor proteins of Streptococcus pneumoniae, Klebsiella pneumoniae, and Acinetobacter baumannii. The physicochemical parameters of these putative AMPs were computed and their 3-D structures were predicted using I-TASSER. These AMPs were subsequently subjected to docking interaction analysis against the identified bacterial pneumonia pathogen proteins using PATCHDOCK.
Identification of candidate plant growth promoting endophytes from Echium plantagineum roots
(University of the Western Cape, 2018) Wu, Ruomou; Keyster, Marshall
The yearly increase of global population will result in a greater demand for crop production, but with the climates changes and a lack of available agricultural land it will become increasingly more difficult to provide sufficient crops to feed everyone adequately. Application of the PGPE has proven over the past researches to be able enhance growth of plants via various growth promoting mechanisms. To identify suitable growth promoting bacteria candidate, E. plantagineum plant was used to isolate endophytes from the root after surface sterilization. The isolates bacteria were used to inoculate Brassica napus L seeds. The effects of isolate's ability to promote growth were evaluated based on the certain growth parameters after 42 days in the green house. Isolate CP5 produced highest results in all growth parameter. Isolates CP5 was selected as potential candidate as significant improvement was shown by this isolate. This isolate was tested for the ability to produce ACC deaminase, solubilize phosphate, synthesize IAA and siderophore production. Furthermore isolate CP5 growth promotion abilities was tested on Brassica napus L under antimony stress.

Browsing by Author "Keyster, Marshall"

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