TITLE:
Concomitant Increases of the Developing Seed Phosphoenolpyruvate Carboxylase Ac-tivity and the Seed Protein Content of Field-Grown Wheat with Nitrogen Supply
AUTHORS:
Naoki Yamamoto, Toshio Sugimoto, Takehiro Masumura
KEYWORDS:
Nitrogen Application, Phosphoenolpyruvate Carboxylase, Seed Storage Protein, Wheat
JOURNAL NAME:
Agricultural Sciences,
Vol.5 No.14,
December
29,
2014
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.