Temporary Application of Nitrate to Nitrogen-Deficient Soybean Plants at the Mid-to Late-Stages of Seed Development Increased the Accumulation of the β-Subunit of β-Conglycinin, a Major Seed Storage Protein

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The accumulation of the β-subunit of β-conglycinin, a major soybean storage protein, in seeds is controlled by the nitrogen (N) status of the plant. When non-nodulating soybean mutants (T201) were hydroponically cultivated under N-sufficient conditions (supply of 5 mM NaNO_3 to the medium), β-subunit accumulation was first detected at 30 d after flowering (DAF). In N-deficient plants (supply of 1 mM NaNO_3), the accumulation of the β-subunit was strongly inhibited. When 5 mM ^<15>N-labeled NO_3^-was supplied for 1 week to N-deficient T201 plants before 28 DAF, the β-subunit protein did not accumulate, but the application of 5 mM NO_3^-after 28 DAF, led to a substantial accumulation of the β-subunit. The total ^<15>N percentage in mature seeds was similar, irrespective of the time of feeding, regardless of the accumulation of the β-subunit. The 7 S (mostly composed of β-conglycinin) and 11 S globulins (mostly glycinin, which was another major component of storage protein) contained N from 5 mM ^<15>5NO_3^-at a similar level, about 60% of total N. These results indicate that a) the temporary supply of a high level of NO_3^-effectively promoted β-subunit accumulation in N-deficient plants when feeding was carried out after 28 DAF, and b) incorporation of fed NO_3^-was similar between 7 S and 11 S globulins.
社団法人日本土壌肥料学会の論文