Endosperm-specific accumulation of human α-lactalbumin increases seed lysine content in maize

Key message This study demonstrated high expression and accumulation of human alpha-lactalbumin in transgenic maize, and significant improvement of lysine content in maize endosperm. As a high-yield crop, lack of lysine in endosperm storage protein is a major defect of maize (Zea mays L.). Specifically expression of foreign proteins is a potential way to improve lysine content in maize endosperm. Human alpha-lactalbumin is such a protein with high lysine content and high nutritional value. In this study, the codon-optimized human lactalbumin alpha (LALBA) gene was driven by maize endosperm-specific 27 kD gamma-zein promoter, and transformed into maize. Five independent transgenic lines were obtained, and LALBA was highly expressed in endosperm in all these lines. Protein assay indicated that human alpha-lactalbumin was highly accumulated in maize endosperm. Immuno-localization assay indicated that human alpha-lactalbumin was mainly deposited into the protein body (PB). Protein interaction assay showed that human alpha-lactalbumin interacted with 16 kD gamma-zein, which might lead to its deposition to the PBs. Amino acid analysis of two independent transgenic lines showed significant increase of lysine contents in transgenic endosperm, with 47.26% and 45.15% increase to their non-transgenic seeds, respectively. We obtained transgenic maize with endosperm-specific accumulation of human alpha-lactalbumin at high level and increased the lysine content in maize endosperm. This study demonstrated an effective way to improve the nutritional value of maize seeds.

Automated summary

This study demonstrated a method to achieve high expression and accumulation of human alpha-lactalbumin in transgenic maize, resulting in a significant improvement of lysine content in maize endosperm. The findings offer an effective approach to enhance the nutritional value of maize seeds.