A selectively terminable transgenic rice line expressing human lactoferrin.

Human lactoferrin (hLF) is a multifunctional milk protein which could be utilized for promoting human health. Transgenic rice has been used as a bioreactor for mass production of recombinant hLF. However, one major concern over such transgenic rice is the risk of its unintended spreading into environment and into our food supplies. Here we report the development of selectively terminable transgenic rice expressing human lactoferrin in seeds. These transgenic rice plants could be selectively terminated by bentazon, a common herbicide used for rice weed control. The hLF expression cassette was constructed into a T-DNA containing the RNA interference cassette suppressing the expression of the rice gene CYP81A6 which detoxifies herbicide bentazon, and the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) cassette which confers to glyphosate tolerance. A transgenic line, named as G281, was identified for its high sensitivity to bentazon, high tolerance to glyphosate, and high expression of hLF. Southern analysis suggested G281 is a single copy insertion event. Field tests demonstrated that G281 plants can be completely killed by a single spray of bentazon at 1000 mg/L, which is safe to regular rice and represents only half of the dose recommended by manufacturer for rice field weed control. Therefore, any G281 contaminations in regular rice could be selectively terminated to make sure it will not enter food or feed supplies.