Production of Marker-free Transgenic Rice (Oryza sativa L.) with Improved Nutritive Quality Expressing AmA1

Background: Rice seed proteins are lacking essential amino acids (EAAs). Genetic engineering off ers a fast and sustainable method to solve this problem as it allows the specifi c expression of heterologous EAA-rich proteins. The use of selectable marker gene is essential for generation of transgenic crops, but might also lead to potential environmental and food safety problems. Therefore, the production of marker-free transgenic crops is becoming an extremely attractive alternative and could contribute to the public acceptance of transgenic crops.Objectives: The present study was conducted to examine whether AmA1 can be expressed specifi cally in rice seeds, and generate marker-free transgenic rice with improved nutritive value.Materials and Methods: AmA1 was transferred into rice using Agrobacterium-mediated co-transformation system with a twin T-DNA binary vector and its integration in rice genome was confi rmed by southern blot. Transcription of AmA1 was analyzed by Real-Time PCR and its expression was verifi ed by western analysis. Protein and amino acid content were measured by the Kjeldahl method and the high-speed amino acid analyzer, respectively.Results: Five selectable marker-free homozygous transgenic lines were obtained from the progeny. The expression ofrecombinant AmA1 was confi rmed by the observation of a 35 kDa band in SDS-PAGE and western blot. Compared to the wild-type control, the total protein contents in the seeds of fi ve homozygous lines were increased by 1.06~12.87%. In addition, the content of several EAAs, including lysine, threonine, and valine was increased signifi cantly in the best expressing line.Conclusions: The results indicated that the amino acid composition of rice grain could be improved by seed-specific expression of AmA1.