Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2001
Publication Date: 2/1/2002
Citation: YANG, S., MORAN, D.L., JIA, H.W., BICAR, E.H., LEE, M., SCOTT, M.P. EXPRESSION OF A SYNTHETIC PORCINE ALPHA-LACTALBUMIN GENE IN THE KERNELS OF TRANSGENIC MAIZE. TRANSGENIC RESEARCH. 2002. v. 11. p. 11-20. Interpretive Summary: Most livestock feed is based on corn, but corn does not provide complete nutrition to animals. This situation is currently remedied by the addition of expensive supplements to feed to create a nutritious diet. The cost of animal feed could be greatly reduced by increasing the nutritional value of corn so that less supplementation is required. One way of making corn more enutritious is to genetically engineer it so that highly nutritious proteins accumulate in the grain. We have constructed two synthetic genes designed to cause a highly nutritious protein from sow's milk called alpha lactalbumin to accumulate in corn grain. We have produced transgenic plants containing these genes and compare the function of these genes in the transgenic plants. Alpha lactalbumin accumulates in the grain of some of these plants. These results indicate that this may be a viable approach to improving the nutritional quality of corn. Ultimately, this research will add value to corn that can be passed on to corn and livestoc producers in the form of increased profits and to consumers in the form of reduced costs for meat products.
Technical Abstract: About 80% of the maize produced in the U.S. and Europe is used for animal feed. The main nutritional limitation of maize used for feed is the content of protein that is digestible, bioavailable and contains an amino acid balance that matches the requirements of animals. In contrast, milk protein has good digestibility, bioavailability and amino acid balance. As san initial effort to create maize optimized as a source of swine nutrition a codon-adjusted version of a gene encoding the milk protein porcine a- lactalbumin was synthesized. Maize expression vectors containing this gene under the control of the Ubi-1 promoter and nos 3' terminator were constructed. These vectors were used to transform maize callus lines that were regenerated into fertile plants. The lactalbumin transgenes were transmitted through meiosis to the sexual progeny of the regenerated plants. Accumulation of porcine a-lactalbumin was detected in callus and kernels from transgenic maize lines that were transformed by pUbi/z- sig/Lactal, a plant expression vector that contains 27 kDa maize gamma-zein signal sequence at the 5' end of the synthetic porcine a-lactalbumin coding sequence. Expression was not observed in kernels or callus from transgenic maize lines that were transformed by pUbi/Lactal, a plant expression vector that does not contains an exogenous protein-targeting signal. This suggests that the signal eptide might play an important role in porcine a- lactalbumin accumulation in transgenic maize kernels.