Pollen Sterility—A Promising Approach to Gene Confinement and Breeding for Genetically Modified Bioenergy Crops

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. OPEN ACCESSAgriculture 2012, 2 296

Transgene Bioconfinement: Don’t Flow There

“…Using this approach, barnase has been used for male sterile plant production in several monocot species including wheat (Triticum aestivum L.) [35], creeping bentgrass (Agrostis stolonifera L.) [36], and rice (Oryza sativa L.) [37]. In wheat, tapetum-specific promoters ca55 (derived from maize (Zea mays L.)), and T72 and E1 (derived from rice) were used to drive barnase expression [35].…”

“…No off-target expression was reported, and the male sterile phenotype was stably inherited in progeny when backcrossed to nontransgenic creeping bentgrass. When barnase was expressed in rice using the pollenspecific promoter Zm13 (derived from maize) [37], transgenic events were crossed to nontransgenic rice. The resulting progeny produced 50% viable nontransgenic pollen.…”

Exploiting Genic Male Sterility in Rice: From Molecular Dissection to Breeding Applications

“…Moreover, the Zm13 is a pollen-specific gene in maize that is expressed in the late stages of pollen development. Fusing the promoter of Zm13 ( Zm13pro ) with the cytotoxic BARNASE gene and transforming into japonica rice background displayed stable male sterility, which indicates the stable expression of the transgene ( Hague et al, 2012 ). Similarly, the gene BoA9 (from Brassica oleracea L.) is a tapetum-specific promoter that is responsible for male fertility.…”

Genetic use restriction technologies: a review

“…Recently, Hague et al . () demonstrated that the Zm13 promoter can drive pollen‐specific expression of the cytotoxic gene barnase in stably transformed rice, resulting in plants with pollen sterility. As it is pollen‐specific and inherited as a single Mendelian trait, pollen sterility could be an effective strategy for gametophytic transgene confinement but it would not be effective against transgene escape through seed scatter and vegetative propagation.…”