Contents and compositions of amino acids in rice grains and their regulation: a review

: Amino acids in cereal grains are important nutrients for both human and animals. Increasing the content of amino acids in the rice grain, especially lysine and other essential amino acids, plays a very important role in improving the nutritional stan-dard of people in the countries with rice as staple food. This paper reviewed some research progresses in the contents and compositions of amino acids in the mature grain of rice and their distribution in the different parts of a grain, the synthesis and metabolism of amino acids in the grain, the role of plant hormones in regulating the synthesis and metabolism of on amino acids, and the effects of environmental factors and cultivation practices on the contents and compositions of amino acids in the grain, and dis-cussed the existing problems and key points for future research. It merits further investigating the temporal (at different filling stages) and spatial (at different parts of a grain) distribution characteristics of the contents and compositions of amino acids in a grain during the filling, their physiological and biochemical mechanism, and cultivation regulation and its principle. Such a study is expected to gain new insight into the mechanism in the formation and distributions of amino acids in a rice grain, and explore a new way to increase the contents of amino acids, especially essential amino acids such as lysine, in milled rice.