Tos17 insertion in NADH-dependent glutamate synthase genes leads to an increase in grain protein content in rice

Abstract

Nutrition from cereal grains sustains human life, and the protein content of rice grains is an important source for humans. Recent forward genetics studies pointed out the significant contribution of NADH-dependent glutamate synthase (NADH-GOGAT) to increased grain protein content in durum wheat. The aim of this work was to investigate the contribution of the two NADH-GOGAT enzymes in rice, NADH-GOGAT1, and NADH-GOGAT2, to rice grain protein content, using a reverse genetics approach. The grain protein content and free amino acid concentration were determined in Tos17 insertion mutants of the structural gene of each protein. We found a significant increase in protein content in the NADH-GOGAT2 mutant and an increase in free amino acid concentration in both the NADH-GOGAT1 and the NADH-GOGAT2 mutants. These results provide the first nutritional characterization of the NADH-GOGAT mutants. Rice containing increased protein and amino acid concentrations may have potential to contribute to improved rice nutrition. Since previous field analysis had indicated a 40% yield reduction in each of the mutants, future work should focus on improving the yield of the mutants.