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2004 World Technology Awards Winners & Finalists
Please describe the work that you are doing that you consider to be the most innovative and of the greatest likely long-term significance.
Maize is the staple diet of many Africans, often being eaten three times a day. Two of the greatest scourges of maize in sub-Saharan Africa are the African endemic Maize streak virus (MSV), and abiotic stresses such as drought and heat. We are developing transgenic maize that are resistant to the virus, which can lead to up to 100% crop losses, and tolerant to drought and other abiotic stresses. As MSV is a DNA virus, unlike most plant viruses which have RNA as their genetic material, previously successful approaches such as the use of the viral coat protein gene, have proven to be ineffective. Our approach has been to use a highly mutated, truncated version of the viral replication-associated protein (Rep) gene and make transgenic plants using as a promoter the highly efficient monocot ubiquitin promoter. A variety of constructs were first tested in tissue culture and those that inhibited MSV replication transformed into a model monocot grass, Digitaria sanguinalis, which is easier to transform and grow in the laboratory than maize. Those that conferred virus resistance on these plants were then transformed into maize. These were tested by an extremely severe test using agroinfection of 3-day old seedlings. Resistant T0 plants were self pollinated and the resultant T1 offspring tested again. The resistant lines are now in a breeding programme to introduce the gene into commercially viable, elite lines of maize. Some of these have been bred for MSV resistance and the effect of the transgene on these plants will be determined.
In the development of maize tolerant to drought and other abiotic stresses we are using genes from the South African indigenous resurrection plant, Xerophyta viscosa. This plant, which grows in cracks in rocks in mountainous regions, can withstand desiccation to 5% relative water content (RWC). Differential display cDNA libraries were used to determine which genes were up- or down-regulated during dehydration. Approximately 30 up- and 30 down-regulated genes were identified. Many of them were sequenced and the data compared with sequences in international gene banks. Among the genes identified were those coding for antioxidants, membrane proteins, osmoprotectants, LEA (late embyogenesis abundant) proteins, transcription factors, signalling proteins, proton ATPase subunits etc. We have chosen a number of these to concentrate on. We first established that the genes were, indeed, expressed during dehydration and which other stresses induced them. This was done at the RNA level, and where we have raised antibodies to the proteins, at the protein level. We have made transgenic plants with genes encoding a membrane protein and an antioxidant (peroxiredoxin) - the latter is localized to the nucleus and binds DNA to protect it from damage, especially due to high light intensity. The former transgenics showed increased resistance to dehydration, heat and salt treatment. Analysis of the latter are underway. In this project we also first test the genes in D. sanguinalis and then in maize. Abiotic stress tolerant maize plants will, as above, be introduced into commercial elite lines.
BSc in Zoology from University of Cape Town (SA),MA in Genetics from Cambridge (UK), PhD in Microbiology from Rhodes University (SA), post-doctoral fellow at Harvard Medical School (USA), visiting fellow at MIT (USA). Lecturer to Assoc. Prof., Genetics Dept, University of the Witwatersrand. Director Laboratory for Molecular and Cell Biology, Council for Scientific and Industrial Research. Head of Microbiology Dept, University of Cape Town (12 years), currently Prof. in Dept Molecular and Cell Biology, UCT. Winner of L'Oreal/UNESCO prize for leading woman scientist in Africa, 2004; Fellow Royal Society of SA., Chair of Board of AATF (African Agricultural Technology Foundation); Board member of ISAAA (Intl Service for Acquisition Agribiotech Applications); past Vice-President SA Academy of Science; winner of FOYSA award (Four Outstanding Young South Africans); member task fource of Interacademy Council on Science and Technology strategies for Improved Agriculture and Food Security in Africa (for the UN). International speaker on GMOs including World Economic Forum, Davos; United Nations as guest of Secretary General Kofi Annan; OECD; European Commission. Author of Genes for Africa, genetically modified crops in the developing world published by UCT Press. Graduated 19 PhD students, most of whom are still working in science.
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