Abstract
Wheat seed storage protein is of great importance for human food. To increase the contents of storage proteins effectively, nitrogen fertilizer at flowering stages is commonly applied. In our previous study, rice phosphoenolpyruvate carboxylase (PEPCase) activity in developing seeds was observed in response to nitrogen application at a flowering stage and was positively correlated to the response of the protein content in seeds of six cultivars. This observation might indicate that the seeds have a biological system for accepting nitrogen in seeds by using PEPCase. To test whether this physiological event occurs in wheat, we examined the PEPCase activity and protein content in field-grown wheat seeds under different nitrogen supply conditions. With only basal dressing, seeds showed lower PEPCase activity and protein content (both 0.90-fold) compared to seeds without basal fertilizer. With ammonium sulfate application at 8.3 and 25 g/m2 at a flowering stage, seeds showed higher PEPCase activity (1.08- and 1.17-fold, respectively) and protein content (1.15- and 1.42-fold, respectively), depending on the nitrogen level. We investigated the relationship between PEPCase activity and protein content in the seeds among four conditions. The effect of the nitrogen supply on PEPCase activity during grain-filling stages was validated by the results of a hydroponic culture experiment. Together the results demonstrate that our hypothesis seems to apply to field-grown wheat.
Highlights
Wheat seeds are an excellent food source
The activities per grain showed a different trend (Figure 1(b)), namely, the activities in the No-basal and Low-N plots were quite similar, increased activity according to the nitrogen supply at the flowering stage was seen. These results showed that the application of nitrogen fertilization at the flowering stage was an effective strategy to induce an increase in phosphoenolpyruvate carboxylase (PEPCase) activity
We tested the relationship between the PEPCase activity and protein content in wheat seeds under the four different growth conditions
Summary
Wheat seeds are an excellent food source. The seeds contain storage proteins, gliadins and glutenins, which have the unique properties and play important roles during the food processing of wheat flour [1]. Wheat flour can be used in a wide range of foods such as bread and noodles. The proteins are the most critical component in the determination of flour quality [2]. The composition and content of the storage proteins have been targeted in wheat cultivation and breeding [3]. Genetic breeding research regarding protein composition and the environmental modulation of the protein content has led to the efficient production of agronomically valuable wheat seeds [1] [4] [5]
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