Magister Scientiae - MSc (Biotechnology)

Permanent URI for this collection

https://hdl.handle.net/10566/13204

Browse

Browsing by Subject "Abiotic stress"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Investigation of the role of AtNOGC1, a guanylyl cyclase protein in response to abiotic and biotic stress
    (University of the Western Cape, 2018) Muthevhuli, Mpho; Mulaudzi-Masuku, Takalani; Iwuoha, Emmanuel; Donaldson, Lara
    Agricultural production is one of the most important sectors which provide food for the growing world population which is estimated to reach 9.7 billion by 2050, thus there is a need to produce more food. Climate change, on the other hand, is negatively affecting major global crops such as maize, sorghum, wheat and barley. Environmental factors such as salinity, drought, high temperatures and pathogens affect plant production by oxidatively damaging the physiological processes in plants, leading to plant death. Poor irrigation used to combat drought result in salinasation, which is estimated to affect 50% of arable land by 2050. Plants have developed several mechanisms that protect them against stress and these include overexpression of stress responsive genes and altered signal transduction to change the expression of stress responsive genes, among others. Cyclic 3’5’ guanosine monophosphate (cGMP), a second messenger that is synthesised by guanylyl cyclase (GC), transmit signals to various cellular functions in plants during plant development, growth and response to abiotic and biotic stresses. Arabidopsis thaliana nitric oxide guanylyl cyclase 1 (AtNOGC1) is a guanylyl cyclase which upon activation by nitric oxide (NO) leads to the production of more cGMP. Cyclic GMP further activates protein kinases, ion gated channels and phosphodiesterase which mediate response to various stresses. In this project the role of AtNOGC1 was investigated in response to abiotic and biotic stresses through analysis of its evolutionary relationships, promoter, gene expression and functional analysis via the viability assays in Escherichia coli (E.coli). Phylogenetic tree, exon-intron structure and conserved motifs were analysed using the Molecular Evolutionary Genetics Analysis (MEGA V.7), Gene Structure Display Server 2.0 (GSDS 2.0), and Multiple Expectation Maximisation for Motif Elicitation (MEME) tools respectively. AtNOGC1’s gene expression was analysed by the Real-Time Quantitative Reverse Transcription Polymerase Reaction (qRT-PCR), whereas functional analysis was carried out using the cell viability (liquid and spot) assays to determine its ability to confer stress tolerance to E. coli.
  • Thumbnail Image
    Item
    Zirconium-induced physiological and biochemical responses in two genotypes of Brassica napus L.
    (University of the Western Cape, 2015) Braaf, Ryan; Keyster, Marshall
    South Africa is one of two countries responsible for the production of approximately 80% of the world’s Zr. The increase in mining activity has detrimental effects on the environment, especially crop plants, as more pollutants are leached into the soil. Consequently, it is necessary to understand how plants respond to this form of abiotic stress. Therefore, this study focused on determining the physiological and biochemical responses of two genotypes of Brassica napus L (Agamax and Garnet) in response to Zr stress. The levels of cell death, lipid peroxidation and ROS were higher in Garnet, whereas the chlorophyll content was higher in Agamax. Furthermore, native PAGE analysis detected seven SOD isoforms and seven APX isoforms in Agamax, compared to 6 SOD isoforms and 7 APX isoforms in Garnet. The results thus indicate that Agamax is tolerant to Zr-induced stress, whereas Garnet is sensitive. An assay for the rapid quantification of Zr within plant samples was subsequently developed, which revealed that Agamax retained the bulk of the Zr within its roots, whereas Garnet translocated most of the Zr to its leaves. The ability of Agamax to sequester Zr in its roots comes forth as one of the mechanisms which confers greater tolerance to Zr-induced stress. As a consequence, our study sought to use the optical, physical and chemical properties of quantum dots to image the uptake and translocation of Zr in B. napus genotypes. ICPOES was also performed to quantify Zr levels in various plant organs. Data from the ICPOES revealed varying patterns of uptake and translocations between Garnet and Agamax. These patterns were similarly shown in IVIS Lumina images, tracing the transport of QD/Zr conjugates. This method ultimately proved to be successful in tracing the uptake of Zr, and could essentially be a useful tool for targeting and imaging a number of other molecules.