Abstract
Advanced genetic and biotechnology tools will be required to realize the full potential of food and bioenergy crops. Given current regulatory concerns, many transgenic traits might never be deregulated for commercial release without a robust gene confinement strategy in place. The potential for transgene flow from genetically modified (GM) crops is widely known. Pollen-mediated transfer is a major component of gene flow in flowering plants and therefore a potential avenue for the escape of transgenes from GM crops. One approach for preventing and/or mitigating transgene flow is the production of trait linked pollen sterility. To evaluate the feasibility of generating pollen sterility lines for gene confinement and breeding purposes we tested the utility of a promoter (Zm13Pro) from a maize pollen-specific gene (Zm13) for driving expression of the reporter gene GUS and the cytotoxic gene barnase in transgenic rice (Oryza sativa ssp. Japonica cv. Nipponbare) as a monocot proxy for bioenergy grasses. This study demonstrates that the Zm13 promoter can drive pollen-specific expression in stably transformed rice and may be useful for gametophytic transgene confinement and breeding strategies by pollen sterility in food and bioenergy crops.
Highlights
The need to improve agricultural production of food and bioenergy crops has been considered by some to be a “moral imperative” [1]
To be useful as a tool in transgene confinement and/or breeding strategies, the Zm13 promoter must be co-expressed with additional trait gene(s) of interest, stably inherited as a single Mendelian trait, and pollen specific without deleterious spurious expression
This construct is the same as the second, except hpt was replaced by bar, which confers tolerance to glufosinate ammonium herbicides, and gusA was replaced by the ribonuclease barnase (Zm13Pro::barnase)
Summary
The need to improve agricultural production of food and bioenergy crops has been considered by some to be a “moral imperative” [1]. Confinement of transgenes is an obvious regulatory and biosafety objective for the release and commercialization of transgenic bioenergy feedstocks [9,10] as the development of fertile reproductive structures in genetically modified perennial plants will result in undesirable gene flow to non-transgenic and wild plants [9,11,12,13,14,15,16]. While recombinase-mediated excision technologies are practical for removal of specific DNA insertions, the inability to use these systems for gene confinement in hybrid plant systems is evident by the lack of reports in peer reviewed and patent literature or practical application in commercial crops. 5' regulatory elements of the Zm13 gene serve as an obvious sequence of interest for creating a TC system in transgenic plants It is the development of TC/hybrid technology using a maize pollen specific promoter (Zm13Pro) that is the purpose of this investigation.
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