Differential response of methionine metabolism in two grain legumes, soybean and azuki bean, expressing a mutated form of Arabidopsis cystathionine ¦Ã-synthase

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• 作者：Moemen S. Hanafy^a ; ¹ ; Shaikh M. Rahman^b ; ² ; Yumi Nakamoto^a ; Toru Fujiwara^c ; Satoshi Naito^d ; Kyo Wakasa^e ; Masao Ishimoto^a ; ^f ; ^{ishimoto@affrc.go.jp}
• 关键词：Azuki bean ; Cystathionine ¦Ã-synthase ; Methionine biosynthesis ; Soybean ; Transgenic plant
• 刊名：Journal of Plant Physiology
• 出版年：2013
• 出版时间：15 February, 2013
• 年：2013
• 卷：170
• 期：3
• 页码：338-345
• 全文大小：526 K

文摘

Methionine (Met) is a sulfur-containing amino acid that is essential in mammals and whose low abundance limits the nutritional value of grain legumes. Cystathionine ¦Ã-synthase (CGS) catalyzes the first committed step of Met biosynthesis, and the stability of its mRNA is autoregulated by the cytosolic concentration of S-adenosyl-l-methionine (SAM), a direct metabolite of Met. The mto1-1 mutant of Arabidopsis thaliana harbors a mutation in the AtCGS1 gene that renders the mRNA resistant to SAM-dependent degradation and therefore results in the accumulation of free Met to high levels in young leaves. To manipulate Met biosynthesis in soybean and azuki bean, we introduced the AtCGS1 mto1-1 gene into the two grain legumes under the control of a seed-specific glycinin gene promoter. Transgenic seeds of both species accumulated soluble Met to levels at least twice those apparent in control seeds. However, the increase in free Met did not result in an increase in total Met content of the transgenic seeds. In transgenic azuki bean seeds, the amount of cystathionine, the direct product of CGS, was markedly increased whereas the total content of Met was significantly decreased compared with control seeds. Similar changes were not detected in soybean. Our data suggest that the regulation of Met biosynthesis differs between soybean and azuki bean, and that the expression of AtCGS1 mto1-1 differentially affects the metabolic stability of sulfur amino acids and their metabolites in the two grain legumes.