Genome editing toward biofortified soybean with minimal trade-off between low phytic acid and yield

Phytic acid (PA) in grain seeds reduces the bioavailability of nutrient elements in monogastric animals, and an important objective for crop seed biofortification is to decrease the seed PA content. Here, we employed CRISPR/Cas9 to generate a PA mutant population targeting PA biosynthesis and transport genes, including two multi-drug-resistant protein 5 (MRP5) and three inositol pentose-phosphate kinases (IPK1). We characterized a variety of lines containing mutations on multiple IPK and MRP5 genes. The seed PA was more significantly decreased in higher-order mutant lines with multiplex mutations. However, such mutants also exhibited poor agronomic performance. In the population, we identified  two lines carrying single mutations in ipk1b and ipk1c, respectively. These mutants exhibited moderately reduced PA content, and regular agronomic performance compared to the wild type. Our study indicates that moderately decreasing PA by targeting single GmIPK1 genes, rather than multiplex mutagenesis toward ultra-low PA, is an optimal strategy for low-PA soybean with a minimal trade-off in yield performance.