High-level Expression of Maize γ-zein Protein in Transgenic Soybean (Glycine max)

The γ-zein gene from maize was introduced into soybean (cultivar ‘Jack’) using the particle inflow gun and three independent, fertile transgenic lines ‘ZA’ ‘ZC’ and ‘BY’ were recovered. Molecular and genetic analyses indicated that the transgenic line ‘ZA’ contains a single copy of γ-zein gene, whereas both transgenic lines ‘ZC’ and ‘BY’ contain multiple copies of the γ-zein gene. Northern and western blot analyses suggested that transgenic seeds from the T1 and T2 progeny of ‘ZA’ and ‘ZC’ expressed γ-zein mRNA and γ-zein protein successfully. However, neither γ-zein mRNA transcripts nor γ-zein protein could be detected from transgenic seeds of ‘BY’ progeny. Transgenic seeds from the T1 and T2 progenies of ‘ZA’ and ‘ZC’ strongly expressed the γ-zein protein (from 597 to 819 ng/mg of dry seed flour), as determined by quantitative ELISA analysis. The percentage of alcohol extractable proteins in total seed proteins ranged between 2.54 and 6.49% in seeds from the transgenic lines expressing γ-zein, whereas the corresponding value in seeds from a non-transformed control line was only 0.35%. Amino acid analysis of T1 and T2 transgenic ‘ZA’ and ‘ZC’ seeds expressing γ-zein protein showed the percentage content of cysteine and methionine increased significantly (from 26.97 to 29.33% and from 15.49 to 18.57%, respectively) compared to non-transformed control seeds of the same line.