UWCScholar :: Browsing by Author "Gokul, Arun"

Browsing by Author "Gokul, Arun"

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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.
Biocontrol Potential of Bacillus subtilis and Bacillus tequilensis against Four Fusarium Species
(MDPI, 2023) Baard, Vejonepher; Bakare, Olalekan Olanrewaju; Daniel, Augustine Innalegwu; Nkomo, Mbukeni; Gokul, Arun
The use of biological control agents as opposed to synthetic agrochemicals to control plant pathogens has gained momentum, considering their numerous advantages. The aim of this study is to investigate the biocontrol potential of plant bacterial isolates against Fusarium oxysporum, Fusarium proliferatum, Fusarium culmorum, and Fusarium verticillioides. Isolation, identification, characterization, and in vitro biocontrol antagonistic assays of these isolates against Fusarium species were carried out following standard protocols. The bacterial endophytes were isolated from Glycine max. L leaves (B1), Brassica napus. L seeds (B2), Vigna unguiculata seeds (B3), and Glycine max. L seeds (B4). The bacterial isolates were identified using 16S rRNA PCR sequencing. A phylogenetic analysis shows that the bacterial isolates are closely related to Bacillus subtilis (B1) and Bacillus tequilensis (B2–B4), with an identity score above 98%. All the bacterial isolates produced a significant amount (p < 0.05) of indole acetic acid (IAA), siderophores, and protease activity. In vitro antagonistic assays of these isolates show a significant (p < 0.05) growth inhibition of the fungal mycelia in the following order: F. proliferatum > F. culmorum > F. verticillioides > F. oxysporum, compared to the control. The results suggest that these bacterial isolates are good biocontrol candidates against the selected Fusarium species
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.
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.
Impact of vanadium stress on physiological and biochemical characteristics in heavy metal susceptible and tolerant Brassicaceae
(University of the Western Cape, 2013) Gokul, Arun; Keyster, Marshall
There is an influx in heavy metals into soils and ground water due to activities such as increased mineral mining, improper watering and the use of heavy metal contaminated fertilizers. These heavy metals are able to increase the ROS species within plants which may result in plant metabolism deterioration and tissue damage. Heavy metals may also directly damage plants by rendering important enzymes non-functional through binding in metal binding sites of enzymes. The heavy metal focused on in this study was vanadium due to South Africa being one of the primary produces of this metal. Two related Brassica napus L cultivars namely Agamax and Garnet which are economically and environmentally important to South Africa were exposed to vanadium. Physiological experiments such as cell death, chlorophyll and biomass determination were conducted to understand how these cultivars were affected by vanadium toxicity. A low cost, sensitive and robust vanadium assay was developed to estimate the amount of vanadium in samples such as water, soils and plant material. The oxidative state as well as the antioxidant profile of the two cultivars were also observed under vanadium stress. A chlorophyll assay which was conducted on the two cultivars exposed to vanadium showed a marked decrease in chlorophyll A in the suspected sensitive cultivar which was Garnet. However, the suspected tolerant cultivar Agamax fared better and the decrease in chlorophyll A was much less. A similar trend was observed for the two cultivars when the cell death assay was conducted. The vanadium assay showed that Garnet had higher concentrations of vanadium within its leaves and lower concentrations in its roots when compared to Agamax. This observation displayed that Agamax had inherent mechanisms which it used to localize vanadium in its roots and which assisted in its tolerance to the vanadium stress. The oxidative state was determined by doing assays for the specific reactive oxygen species namely hydrogen peroxide and superoxide. It was observed that vanadium treated Garnet leaves had higher reactive oxygen species (ROS) production when compared to the Agamax treated leaves. In-gel native PAGE activity gels were conducted to determine the antioxidant profile for the two cultivars which were exposed to vanadium. The antioxidant enzymes which were under investigation were ascorbate peroxide (APX), superoxide dismutase (SOD) and glutathione-dependent peroxidases (GPX-like) as these enzymes are known to be responsible for controlling the ROS produced in the plants. The GPX-like profile consisted of three isoforms. No isoforms were inhibited by vanadium treatments but one isoform had increased activity in both the Garnet and Agamax treated samples. The SOD profile for Garnet consisted of six isoforms and Agamax had seven isoforms. One isoform which was visualized in both Agamax as well as Garnet was inhibited by vanadium treatments. Agamax also had two isoforms which were up-regulated however the corresponding isoforms in Garnet showed no change. The Ascorbate peroxidase profile consisted of seven isoforms for both Garnet and Agamax. No isoforms were inhibited by vanadium treatment. Three isoforms were up-regulated in Garnet and Agamax under vanadium treatments. Here, it is illustrated that Garnet lacked certain mechanisms found in Agamax (and thus experienced more cell death, yield and chlorophyll loss) and performed worst under high vanadium concentrations. Although Garnet increased the activity of some of its antioxidant isoforms in response to increasing ROS levels it was not adequate to maintain a normal oxidative homeostasis. This disruption in oxidative homeostasis lead to plant damage. Agamax was observed to produce less ROS than Garnet and was able to control the ROS produced more effectively than Garnet and thus less damage was observed in Agamax.
Inhibition of NOS- like activity in maize alters the expression of genes involved in H2O2 scavenging and glycine betaine biosynthesis
(Nature Publishing Group, 2018) Phillips, Kyle; Majola, Anelisa; Gokul, Arun; Keyster, Marshall; Ludidi, Ndiko; Egbichi, Ifeanyi
Nitric oxide synthase-like activity contributes to the production of nitric oxide in plants, which controls plant responses to stress. This study investigates if changes in ascorbate peroxidase enzymatic activity and glycine betaine content in response to inhibition of nitric oxide synthase-like activity are associated with transcriptional regulation by analyzing transcript levels of genes (betaine aldehyde dehydrogenase) involved in glycine betaine biosynthesis and those encoding antioxidant enzymes (ascorbate peroxidase and catalase) in leaves of maize seedlings treated with an inhibitor of nitric oxide synthase-like activity. In seedlings treated with a nitric oxide synthase inhibitor, transcript levels of betaine aldehyde dehydrogenase were decreased. In plants treated with the nitric oxide synthase inhibitor, the transcript levels of ascorbate peroxidase-encoding genes were down-regulated. We thus conclude that inhibition of nitric oxide synthase-like activity suppresses the expression of ascorbate peroxidase and betaine aldehyde dehydrogenase genes in maize leaves. Furthermore, catalase activity was suppressed in leaves of plants treated with nitric oxide synthase inhibitor; and this corresponded with the suppression of the expression of catalase genes. We further conclude that inhibition of nitric oxide synthase-like activity, which suppresses ascorbate peroxidase and catalase enzymatic activities, results in increased H2O2 content.
Piperonylic acid alters growth, mineral content accumulation and reactive oxygen species-scavenging capacity in chia seedlings
(Oxford University Press, 2022) Nkomo, Mbukeni; Gokul, Arun; Ndimba, Roya
p-Coumaric acid synthesis in plants involves the conversion of phenylalanine to trans-cinnamic acid via phenylalanine ammonia-lyase (PAL), which is then hydroxylated at the para-position under the action of trans-cinnamic acid 4-hydroxylase. Alternatively, some PAL enzymes accept tyrosine as an alternative substrate and convert tyrosine directly to p-coumaric acid without the intermediary of trans-cinnamic acid. In recent years, the contrasting roles of p-coumaric acid in regulating the growth and development of plants have been well-documented. To understand the contribution of trans-cinnamic acid 4-hydroxylase activity in p-coumaric acid-mediated plant growth, mineral content accumulation and the regulation of reactive oxygen species (ROS), we investigated the effect of piperonylic acid (a trans-cinnamic acid 4-hydroxylase inhibitor) on plant growth, essential macroelements, osmolyte content, ROS-induced oxidative damage, antioxidant enzyme activities and phytohormone levels in chia seedlings. Piperonylic acid restricted chia seedling growth by reducing shoot length, fresh weight, leaf area measurements and p-coumaric acid content. Apart from sodium, piperonylic acid signifcantly reduced the accumulation of other essential macroelements (such as K, P, Ca and Mg) relative to the untreated control. Enhanced proline, superoxide, hydrogen peroxide and malondialdehyde contents were observed. The inhibition of trans-cinnamic acid 4-hydroxylase activity signifcantly increased the enzymatic activities of ROS-scavenging enzymes such as superoxide dismutase, ascorbate peroxidase, catalase and guaiacol peroxidase. In addition, piperonylic acid caused a reduction in indole-3-acetic acid and salicylic acid content. In conclusion, the reduction in chia seedling growth in response to piperonylic acid may be attributed to a reduction in p-coumaric acid content coupled with elevated ROS-induced oxidative damage, and restricted mineral and phytohormone (indole-3-acetic acid and salicylic) levels.
Plant antimicrobial peptides (pamps): Features, applications, production, expression and challenges
(MDPI, 2022) Bakare, Olalekan Olanrewaju; Gokul, Arun; Fadaka, Adewale Oluwaseun
The quest for an extraordinary array of defense strategies is imperative to reduce the challenges of microbial attacks on plants and animals. Plant antimicrobial peptides (PAMPs) are a subset of antimicrobial peptides (AMPs). PAMPs elicit defense against microbial attacks and prevent drug resistance of pathogens given their wide spectrum activity, excellent structural stability, and diverse mechanism of action. This review aimed to identify the applications, features, production, expression, and challenges of PAMPs using its structure–activity relationship. The discovery techniques used to identify these peptides were also explored to provide insight into their significance in genomics, transcriptomics, proteomics, and their expression against disease-causing pathogens.
PR-1-Like Protein as a Potential Target for the Identification of Fusarium oxysporum: An In Silico Approach
(BioTech, 2021-07) Bakare, Olalekan Olanrewaju; Gokul, Arun; Keyser, Marshall
Fusarium oxysporum remains one of the leading causes of economic losses and poor crop yields; its detection is strained due to its presentation in various morphological and physiological forms. This research work sought to identify novel biomarkers for the detection of Fusarium oxys porum using in silico approaches. Experimentally validated anti-Fusarium oxysporum antimicrobial peptides (AMPs) were used to construct a profile against Fusarium oxysporum. The performance and physicochemical parameters of these peptides were predicted. The gene for the Fusarium oxysporum receptor protein PR-1-like Protein, Fpr1, was identified and translated. The resulting protein model from the translation was then validated. The anti Fusarium oxysporum AMPs and Fusarium oxysporum receptor protein 3-D structures were characterized, and their docking interaction analyses were carried out. The HMMER in silico tool identified novel anti-Fusarium oxysporum antimicrobial peptides with good performance in terms of accuracy, sensitivity, and specificity. These AMPs also displayed good physicochemical properties and bound with greater affinity to Fusarium oxysporum protein receptor PR-1-like Protein. The tendency of these AMPs to precisely detect Fusarium oxysporum PR-1-like Protein, Fpr1, would justify their use for the identification of the fungus. This study would enhance and facilitate the identification of Fusarium oxysporum to reduce problems associated with poor crop yield, economic losses, and decreased nutritional values of plants to keep up with the growing population.
The Relationship between Cadmium Toxicity and the Modulation of Epigenetic Traits in Plants
(International Journal of Molecular Sciences, 2021-06) Niekerk, Lee- Ann; Bakare, Olalekan Olanrewaju; Carelse, Mogamat Fahiem; Keyser, Marshall; Mavumengwana, Vuyo; Gokul, Arun
Elevated concentrations of heavy metals such as cadmium (Cd) have a negative impact on staple crop production due to their ability to elicit cytotoxic and genotoxic effects on plants. In order to understand the relationship between Cd stress and plants in an effort to improve Cd tolerance, studies have identified genetic mechanisms which could be important for conferring stress tolerance. In recent years epigenetic studies have garnered much attention and hold great potential in both improving the understanding of Cd stress in plants as well as revealing candidate mechanisms for future work. This review describes some of the main epigenetic mechanisms involved in Cd stress responses. We summarize recent literature and data pertaining to chromatin remodeling, DNA methylation, histone acetylation and miRNAs in order to understand the role these epigenetic traits play in cadmium tolerance. The review aims to provide the framework for future studies where these epigenetic traits may be used in plant breeding and molecular studies in order to improve Cd tolerance.
Sustainable agriculture through the enhancement of microbial biocontrol agents: Current challenges and new perspectives
(MDPI, 2023) Gokul, Arun; Mabaso, Jabulani; Klein, Ashwil
The future of pesticide usage in agriculture is uncertain due to its unsustainability, adverse environmental impacts, and its association in enhanced phytopathogen resistance. Hence, this situation urges the development of new sustainable practices in agriculture. A promising approach involves endophytes, which are non-pathogenic microorganisms inhabiting the interior parts of plants. However, due to the vast diversity and complexity of plant microbiomes, a major gap has formed with regards to endophytic research and its application in phytopathogen biocontrol. The gap has mainly been increasing due to the difficulty of isolating underrepresented endophytes and due to limitation of previous genetic tools availability to further research and understand plant-microbe interaction, endophytic biocontrol capabilities and their biocontrol compounds.
Using biochemical and nutrient analysis to understand the role of methylglyoxal signalling in soybean exposed to zirconium
(University of the Western Cape, 2017) Ndlovu, L.E.G; Keyster, Marshall; Gokul, Arun
Soybean have been listed as a priority commodity crop in South Africa (SA) and provide a good source of protein to the population. Therefore, soybean has been earmarked as an important food security crop and strategies are currently being discussed at governmental level to increase and sustain soybean production.

Browsing by Author "Gokul, Arun"

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