Browsing by Author "Harjeet, Khanna"

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    Golden bananas in the field: elevated fruit pro-vitamin A from the expression of a single banana transgene
    (Plant Biotechnology Journal, 2017) Jean-Yves, Paul; Harjeet, Khanna; Kleidon, Jennifer; Hoang, Phuong; Geijskes, Jason; Daniells, Jeff; Zaplin, Ella; Rosenberg, Yvonne; James, Anthony; Bulukani, Mlalazi; Pradeep, Deo; Arinaitwe, Geofrey; Namanya, Priver; Becker, Douglas; Tindamanyire, James; Tushemereirwe, Wilberforce; Harding, Robert; Dale, James
    Vitamin A deficiency remains one of the world's major public health problems despite food fortification and supplements strategies. Biofortification of staple crops with enhanced levels of pro-vitamin A (PVA) offers a sustainable alternative strategy to both food fortification and supplementation. As a proof of concept, PVA-biofortified transgenic Cavendish bananas were generated and field trialed in Australia with the aim of achieving a target level of 20 μg/g of dry weight (dw) β-carotene equivalent (β-CE) in the fruit. Expression of a Fe'i banana-derived phytoene synthase 2a (MtPsy2a) gene resulted in the generation of lines with PVA levels exceeding the target level with one line reaching 55 μg/g dw β-CE. Expression of the maize phytoene synthase 1 (ZmPsy1) gene, used to develop ‘Golden Rice 2’, also resulted in increased fruit PVA levels although many lines displayed undesirable phenotypes. Constitutive expression of either transgene with the maize polyubiquitin promoter increased PVA accumulation from the earliest stage of fruit development. In contrast, PVA accumulation was restricted to the late stages of fruit development when either the banana 1-aminocyclopropane-1-carboxylate oxidase or the expansin 1 promoters were used to drive the same transgenes. Wild-type plants with the longest fruit development time had also the highest fruit PVA concentrations. The results from this study suggest that early activation of the rate-limiting enzyme in the carotenoid biosynthetic pathway and extended fruit maturation time are essential factors to achieve optimal PVA concentrations in banana fruit.
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    Inhibition of cell death as an approach for development of transgenic resistance against Fusarium wilt disease
    (African Journal of Biotechnology, 2016) Magambo, Betty; Harjeet, Khanna; Arinaitwe, Geofrey; Tendo, Sali; Arinaitwe, Ivan Kabiita; Kubiriba, Jerome; Tushemereirwe, Wilberforce; Dale, James
    Fusarium oxysporum f. sp. cubense (Foc) is one of the major threats to dessert banana (Musa spp.) production. In Uganda, ‘Sukali Ndiizi’ is one of the most popular dessert banana cultivars and it is highly susceptible to Fusarium wilt. Development of resistant cultivars through transgenic approaches has shown to offer one of the most effective control options for most diseases. The transgenic approaches for providing plant disease resistance have mainly been through either enzymatic destruction of pathogen structures, neutralization of pathogen and its products or production of metabolites that eventually kill the pathogen. However in recent years, methods that prevent cell death of host plant after infection especially for necrotrophic pathogens like F. oxysporum have registered success in providing resistance in several crops. We investigated whether the transgenic expression of a programmed cell death inhibition gene in Sukali Ndiizi could be used to confer Fusarium resistance to Foc race 1. Embryogenic cell suspensions of cv. ‘Sukali Ndiizi, were stably transformed with a synthetic, plant-codon optimise mCed-9 gene. Twenty-eight independently transformed plant lines were regenerated. The lines were inoculated with Foc race 1 and observed for 13 weeks in small-plant glasshouse. Three transgenic lines showed significantly lower internal and external disease symptoms than the wild-type susceptible ‘Sukali Ndiizi’ banana plants used as controls. This is the first report from Africa on the generation of Fusarium wilt tolerant transgenic ‘Sukali Ndiizi’, a very popular but rapidly diminishing African dessert banana.