Controlling transgene escape in genetically modified grasses

Luo, Hong (A) Hu, Qian (A) Nelson-Vasilchik, Kim (A) Longo, Chip (A) Kausch, Albert P. (A)
Affiliations: (A): HybriGene Inc.

Trait improvement of turfgrass through genetic engineering is important to the turfgrass industry and the environment. New genes can be introduced into turf that confer desirable traits such as, drought and stress tolerance, insect and pest resistance as well as environmental qualities such as phyto-remediation. However, The possibility for transgene escape to wild and non-transformed species raises commercial and ecological concerns. Male sterility provides a method for the prevention of transgene escape. We have designed and synthesized chimeric gene constructs consisting of a rice tapetum-specific promoter (TAP) fused to either a ribonuclease gene barnase, or the antisense of a rice tapetum-specific gene rts. Both constructs were linked to the bar gene for selection by resistance to the herbicide bialaphos. Using Agrobacterium, we have successfully introduced those gene constructs into creeping bentgrass, producing a total of 221 stably transformed individual events. Tapetum-specific expression of barnase and antisense genes did not affect the vegetative phenotype compared with the control plants, and male-sterile flowers were obtained with both constructs. Microscopic studies confirmed the failure of mature pollen formation in male-sterile transgenics. Mendelian segregation of herbicide resistance and male-sterility has been observed in T1 generation plants derived from crosses with wild type plants. Similar results have also been obtained for perennial ryegrass, tall fescue and bluegrass. The success in producing male-sterile transgenic grasses provides an effective way to measure and control transgene escape from genetically modified plants and should facilitate the production of environmentally responsible grasses with enhanced traits.