Abstract
The major storage protein of rice seeds is glutelin, which comprises various subunits. Changes in the subunit composition of glutelin can greatly affect the nutritional quality of rice. Even though our previous studies demonstrated that the subunit composition was changed by altered nitrogen and sulfur metabolism using transgenic plants expressing a sulfur-rich protein and a detached ear culture method, the response of intact plants was unknown. In this report, intact rice plants were analyzed and found to change their subunit composition following high levels of nitrogen fertilization using conventional sandy soil and hydroponic culture systems. The excess nitrogen treatment in the sandy soil culture reduced GluA subunits and increased GluB subunits, which contain more lysine. And thus the excess nitrogen treatment was estimated to increase the lysine content by 7% compared to the standard treatment. The effect of sulfur metabolism on the subunit composition was uncertain in this study. In consequence, the subunit composition modified by the nitrogen metabolism control was crucial for the nutritional quality improvement of the seeds of intact rice plants.
