CRISPR/Cas9-mediated knockout of E4 gene promotes maturation in soybean

Soybean is a broadly popular and extensively cultivated crop, however, many high-yield and high-quality varieties require specific growth conditions, restricting their widespread adoption. The appropriate light conditions and photoperiod must be attained for these varieties to thrive in new environments. In this study, we employed CRISPR/Cas9 to design two sgRNAs aimed at knocking out the maturity-related gene E4 in a major American soybean variety called ''Jack'', which belongs to maturity group MGII. E4 gene is primarily involved in the photoperiodic flowering and maturity in soybean, making it an ideal candidate for genetic manipulation. We successfully obtained 1 homozygous E4-SG1 mutant type with 1-bp insertion, and 4 homozygous E4-SG2 mutants type with 2-bp deletion, 7-bp deletion, 61-bp deletion, and 1-bp insertion, respectively. The homozygous e4 mutant plants contained early termination codons devoid of transgenic elements. Additionally, no potential off-target sites of the E4 gene were detected. A comparative analysis revealed that, unlike the wild-type, the maturity time of homozygous e4 mutants was early under both short-day and long-day conditions. These mutants offer novel germplasm resources that may be used to modify the photoperiod sensitivity and maturity of soybean, enhancing its adaptability to high-latitude regions.