Engineering sulfur storage in maize seed proteins without apparent yield loss

Area of Science:

• Agricultural Biotechnology
• Plant Molecular Biology
• Nutritional Biochemistry

Background:

• Sulfur assimilation is crucial for amino acid synthesis, impacting protein quality in crops.
• Methionine and cysteine are essential amino acids often limiting in maize zein proteins.
• Genetic strategies can enhance sulfur assimilation pathways to improve crop nutritional profiles.

Purpose of the Study:

• To investigate if deregulating sulfate reduction capacity in maize can increase methionine accumulation in seeds.
• To assess the impact of enhanced sulfur assimilation on zein protein expression and overall seed protein sulfur content.
• To evaluate the nutritional benefits of modified maize in animal feeding trials.

Main Methods:

• Development of transgenic maize expressing Escherichia coli 3'-phosphoadenosine-5'-phosphosulfate reductase (EcPAPR) for enhanced sulfate reduction.
• Analysis of methionine and total protein sulfur content in transgenic kernels.
• Evaluation of 10-kDa δ-zein and other zein protein expression levels.
• Conducting chick feeding trials to compare weight gain on transgenic versus nontransgenic maize.

Main Results:

• Transgenic maize exhibited deregulated sulfate reduction capacity with significantly higher methionine accumulation in seeds (up to 57.6% increase).
• Increased expression of methionine-rich 10-kDa δ-zein and elevated total protein sulfur were observed without negatively affecting other zeins.
• Chick feeding trials showed significant weight gain in birds fed with PE5 transgenic maize compared to controls.
• No apparent yield loss was observed in the transgenic maize lines.

Conclusions:

• Enhanced sulfur assimilation via EcPAPR expression effectively increases methionine content in maize seeds.
• This genetic modification improves the nutritional value of maize, particularly for sulfur-containing amino acids.
• The findings suggest a viable strategy to enhance crop nutritional quality and reduce reliance on costly feed supplements in animal agriculture.