Browsing by Author "Jean-Yves Paul"

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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, 1016-12-15) Jean-Yves Paul; Harjeet Khanna; Jennifer Kleidon; Phuong Hoang; Jason Geijskes; Jeff Daniells; Ella Zaplin; Yvonne Rosenberg; Anthony James; Bulukani Mlalazi; Pradeep Deo; Geofrey Arinaitwe; Priver Namanya; Douglas Becker; James Tindamanyire; Wilberforce Tushemereirwe; Robert Harding; James Dale
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 lg/g of dry weight (dw) b-carotene equivalent (b-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 lg/g dw b-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.
Inhibition of Agrobacterium-Induced Cell Death by Antiapoptotic Gene Expression Leads to Very High Transformation Efficiency of Banana
(Molecular Plant-Microbe Interactions, 2007-06-09) Harjeet K. Khanna; Jean-Yves Paul; Robert M. Harding; Martin B. Dickman; James L. Dale
The death of plant cells in culture following exposure to Agrobacterium tumefaciens remains a major obstacle in de- veloping Agrobacterium-mediated transformation into a highly efficient genotype-independent technology. Here, we present evidence that A. tumefaciens exposure induces cell death in banana cell suspensions. More than 90% of em- bryogenic banana cells died after exposure to A. tumefaciens and cell death was accompanied by a subset of features associated with apoptosis in mammalian cells, including DNA laddering, fragmentation, and formation of apoptotic- like bodies. Importantly, these cellular responses were inhibited in cells expressing the animal antiapoptosis genes Bcl-xL, Bcl-2 3′ untranslated region, and CED-9. Inhibition of cell death resulted in up to 90% of cell clumps trans- formed with Bcl-xL, a 100-fold enhancement over vector controls, approaching the transformation and regeneration of every “transformable” cell. Similar results using sugar- cane, a crop plant known for recalcitrance to Agrobacterium transformation, suggest that antiapoptosis genes may inhibit these phenomena and increase the transformation frequency of many recalcitrant plant species, including the major monocot cereal crop plants. Evidence of inhibition of plant cell death by cross-kingdom antiapoptotic genes also contributes to the growing evidence that genes for con- trol of programmed cell death are conserved across wide evolutionary distances, even though these mechanisms are not well understood in plants.