Submitted to: Transgenic Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/30/2006
Publication Date: 1/11/2007
Citation: Scott, M.P., Peterson, J.M., Moran, D.L., Sangtong, V., Swain, L., Guillumine, P. 2007. A wheat genomic fragment functions as a gametophytic mutant to reduce pollen transmission of transgenic maize loci. Transgenic Research. 16:629-643. Interpretive Summary: Maize pollen is produced by a male flower called a tassel and is carried by wind and gravity to the female flower to produce an ear. The genes of the male plant are transmitted to the kernels produced on the female plant when this occurs. It is possible for pollen to be blown or carried into neighboring fields causing genes to be inadvertantly transferred into grain where they may not be expected or desired. Genes for grain color and certain transgenes can reduce the value of grain intended for certain uses if transferred by inadvertant pollination. We have identified a gene that reduces transfer of transgene loci by pollen. In this study, we report that this gene functions by interfering with pollen development. We also demonstrate the use of this gene to reduce the pollen transmission of a herbicide resistance transgene, providing proof of concept for the idea that transmission of transgenes through pollen can be controlled by a transgene-induced gametophytic mutation. This research will benefit maize producers by providing a tool that can be used to control pollen transmission of transgenes. It will benefit consumers by increasing the quality and safety of the US corn crop.
Technical Abstract: A genomic DNA fragment from wheat carrying the Glu-1Dx5 gene exhibiting reduced pollen transmission in transgenic maize has been reported (Sangtong et al., 2002). To localize the region of the DNA fragment responsible for this reduced pollen transmission, we made transgenic plants in which the sequence 5’ of the 1Dx5 coding sequence is replaced with the maize 27 kD gamma-zein promoter. Like the Glu-1Dx5 transgene, this transgene functioned to produce 1Dx5 in maize endosperm, however, with this transgene, pollen transmission of transgene loci was normal. We conclude that the sequence 5’ of the wheat 1Dx5 coding sequence is required for abnormal pollen transmission. Pollen of Glu-1Dx5 transgenic plants with no pollen transmission of the transgene loci displayed two morphological classes. Moreover, one of these classes had reduced germination. Examination of a bulk sample of the pollen from plants with reduced pollen transmission of transgene loci revealed presence of the transgene in the pollen. A likely hypothesis for the reduction in pollen transmission is therefore that the transgene interferes with pollen development, acting as a gametophytic mutation. We demonstrate that the wheat genomic DNA fragment can be used to control pollen transmission and an herbicide resistance transgene that is genetically linked to it. The wheat genomic DNA fragment or other transgene-induced gametophytic mutations may be useful for controlling pollen transmission of transgene loci in maize grain and seed production.