Role of O-acetyl-l-serine in the coordinated regulation of the expression of a soybean seed storage-protein gene by sulfur and nitrogen nutrition |
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Authors: | Hoyeun Kim Masami Yokota Hirai Hiroaki Hayashi Mitsuo Chino Satoshi Naito Toru Fujiwara |
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Institution: | (1) Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan, JP;(2) Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan, JP |
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Abstract: | The composition of seed storage proteins is regulated by sulfur and nitrogen supplies. Under conditions of a low sulfur-to-nitrogen
ratio, accumulation of the β-subunit of β-conglycinin, a sulfur-poor seed storage protein of soybean (Glycine max L.] Merr.), is elevated, whereas that of glycinin, a sulfur-rich storage protein, is reduced. Using transgenic Arabidopsis thaliana L.] Heynh., it was found that the promoter from the gene encoding the β-subunit of β-conglycinin up-regulates gene expression
under sulfur deficiency and down-regulates gene expression under nitrogen deficiency. To obtain an insight into the metabolic
control of this regulation, the concentrations of metabolites related to the sulfur assimilation pathway were determined.
Among the metabolites, O-acetyl-l-serine (OAS), one of the precursors of cysteine biosynthesis, accumulated to higher levels under low-sulfur and high-nitrogen
conditions in siliques of transgenic A. thaliana. The pattern of OAS accumulation in response to various levels of sulfur and nitrogen was similar to that of gene expression
driven by the β-subunit promoter. Elevated levels of OAS accumulation were also observed in soybean cotyledons cultured under
sulfur deficiency. Moreover, OAS applied to in-vitro cultures of immature soybean cotyledons under normal sulfate conditions
resulted in a high accumulation of the β-subunit mRNA and protein, whereas the accumulation of glycinin was reduced. These
changes were very similar to the responses observed under conditions of sulfur deficiency. Our results suggest that the level
of free OAS mediates sulfur- and nitrogen-regulation of soybean seed storage-protein composition.
Received: 6 February 1999 / Accepted: 16 March 1999 |
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Keywords: | O-Acetyl-l-serine Arabidopsis (transgenic) β -Conglycinin (β -subunit) Glycine (storage protein) Storage protein Sulfur deficiency |
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