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A sorghum gene SbLRR2, which is predicted to encode a simple extracellular leucine-rich repeat (LRR) protein, was previously isolated among a collection of fungal pathogen-induced sorghum cDNA clones generated by suppression subtractive hybridization. Phylogenetic analysis revealed that they are distinct from the simple extracellular LRR proteins reported previously. Subcellular localization analysis demonstrated that the SbLRR2-EYFP fusion protein was targeted to the extracellular space in tobacco leaf cells. Peptide N-Glycosidase F treatment revealed that the SbLRR2 is N-glycosylated with non-fucosylated oligosaccharides when transiently expressed in Nicotiana benthamiana leaves. Functional analysis was performed in SbLRR2 over-expression (OE) Arabidopsis plants which showed enhanced resistance against the necrotrophic pathogens Botrytis cinerea and Alternaria brassicicola. In addition, the OE lines were found to have elevated expression of several jasmonate acid (JA)-associated genes and higher endogenous JA contents. Hence, the SbLRR2-mediated defense responses in transgenic Arabidopsis are likely to be dependent on JA-signaling through increased JA production. On the other hand, the OE lines remained susceptible to Pseudomonas syringae pv. tomato as the wild type plants. Consistently, there was no up-regulation of salicylic acid (SA) defense marker gene expression or SA levels in the OE lines. Using yeast two-hybrid analysis, SbLRR2 was further shown to interact with Arabidopsis hypersensitive-induced response protein 1. Such interaction may suppress hypersensitive response which is known to enhance necrotrophic pathogen invasion. These data suggested a positive regulatory role of SbLRR2 in plant defense. Further phenotypic analysis of transgenic SbLRR2 revealed its novel role in enhancing lead [Pb(II)] tolerance in Arabidopsis. OE-lines were showed to alleviate Pb(II)-induced root inhibition, reduce the accumulation of Pb(II), and enhance transcription of AtPDR12 which was previously shown to function as a potential Pb(II) efflux pump contributing to Pb(II) detoxification. However, all the Pb(II) tolerance responses were abolished when SbLRR2 was transformed into the atpdr12 mutant. Meanwhile, the extracellular localization of SbLRR2 was shown to be essential for the enhanced Pb(II) tolerance in transgenic Arabidopsis. Together, these results indicated that SbLRR2-mediated Pb(II) tolerance was dependent on AtPDR12 via Pb(II) extrusion. Further investigations revealed the Pb(II)-induced transcriptional activation of SbLRR2 and several highly conserved AtPDR12 homologs in sorghum seedlings, suggesting the possibilities of a common molecular mechanism for Pb(II) tolerance in diverse plant species. Finally, an iTRAQ-based LC-MS/MS quantitative proteomics approach was used to investigate of lead responses in Arabidopsis. A total of 114 proteins showed significant changes in protein abundance with 58 up-regulated and 56 down-regulated proteins. Analysis of changes in the protein profile revealed that the photosynthesis, photorespiration and protein biosynthesis in Arabidopsis were inhibited under lead toxicity. On the other hand, abundances of proteins involved in the antioxidant system, glucosinolate-myrosinase system and JA biosynthesis pathway were elevated upon Pb(II) treatment. Further investigation revealed that Pb(II) stress induced a rapid increase of JA contents in Arabidopsis whereas a JA biosynthesis deficient mutant (AOS) showed hypersensitivity to Pb(II) toxicity, strongly implicating a significant role of JA in Pb(II) response. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Call number: LD2668 .T4 1955 P75 / Master of Science

published_or_final_version / abstract / Botany / Doctoral / Doctor of Philosophy

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Call number: LD2668 .T4 1986 L42 / Master of Science / Genetics Interdepartmental Program

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Thesis (M.Sc. Agric. (Crop Science)) --University of Limpopo, 2013 / The study aims to provide insights into the nature and extent of development funding provided to various poverty eradication projects by the National Development Agency (NDA) and its subsequent impact on reducing poverty in the predominantly rural communities of the Makhuduthamaga Municipality in the Limpopo Province. It examines in detail the impact made by the NDA on community development through the disbursement of funds to poverty eradication projects. It also provides insights into the total number of the NDA-funded projects and the total proportion of the NDA-funds allocated to them in the Makhuduthamaga Municipality. The study further examines the nature of the NDA support regarding the design of the interventions, relevance, participation of communities, delivery modalities and sustainability. The effectiveness of the NDA-funded projects in community development is determined using employment opportunities created, income generated, skills transferred, assets accumulated, sustainability mechanisms and community empowerment indicators. Although all of these indicators are found to be tightly linked to the NDA’s mandate of poverty eradication, the extent to which the NDA has achieved its objectives in disbursing development funding earmarked for poverty eradication and strengthening of CSOs was yet to be determined, hence the relevance of this study. The study, therefore, highlights key issues regarding the types of employment opportunities created and levels of income emanating from the NDA-funded projects. The study further highlights various areas of community empowerment, financial and sustainability measures put in place for the sustainability of the NDA-funded projects. Using a combined method of research, that is the qualitative and quantitative case study approach, the study highlights in detail insights into the impact made by the NDA on community development, particularly on Makhuduthamaga Municipality. The study highlights that while the NDA made some strides in the creation of employment opportunities, income generation, food security and community empowerment, both financial and institutional sustainability proved to be a daunting challenge for the NDA-funded projects Tailor-made and accredited training interventions coupled with the introduction of market-driven products to the NDA-funded projects as opposed to heavy reliance on donor funding will go a long way in bringing about productivity and, most probably, positive balance sheets and the maximum impact on the NDA funded projects.