Search

Soybean (Glycine max (L.) Merr.) oil is an important source of vegetable oil for supporting the human diet. However, the high level of polyunsaturated fatty acids in natural soybean oil renders the oil unstable and thus susceptible to the development of unpalatable flavors and trans fatty acids. Therefore, reducing the content of polyunsaturated fatty acids and increasing the content of monounsaturated fatty acids is a longstanding and important target for soybean breeding. However, soybean varieties with a high oleic acid content are rare in soybean germplasm resources, which introduces substantial difficulties in the cultivation of high-oleic-acid soybeans. In this study, CRISPR/Cas9-mediated gene-editing technology was used to create targeted knockout of the soybean fatty acid desaturase encoding genes GmFAD2-1A and GmFAD2-1B that contribute to the formation of polyunsaturated fatty acids. We obtained fad2-1a, fad2-1b, and fad2-1a/fad2-1b homozygous mutants using two sgRNAs. We found that the oleic acid content increased from 11% to 40-50% in the fad2-1a and fad2-1b mutants and to 85% in the fad2-1a/fad2-1b mutants. We also generated transgene-free double mutants that conferred higher oleic acid, and the fad2-1a/fad2-1b mutant had no adverse phenotyping compared with the wild type. Our study provided new materials for the selection and breeding of high-oleic-acid soybean varieties. [ABSTRACT FROM AUTHOR]

Photoperiodic flowering is an important agronomic trait that determines adaptability and yield in soybean and is strongly influenced by FLOWERING LOCUS T (FT) genes. Due to the presence of multiple FT homologs in the genome, their functions in soybean are not fully understood. Here, we show that GmFT3b exhibits functional redundancy in regulating soybean photoperiodic flowering. Bioinformatic analysis revealed that GmFT3b is a typical floral inducer FT homolog and that the protein is localized to the nucleus. Moreover, GmFT3b expression was induced by photoperiod and circadian rhythm and was more responsive to long-day (LD) conditions. We generated a homozygous ft3b knockout and three GmFT3b-overexpressing soybean lines for evaluation under different photoperiods. There were no significant differences in flowering time between the wild-type, the GmFT3b overexpressors, and the ft3b knockouts under natural long-day, short-day, or LD conditions. Although the downstream flowering-related genes GmFUL1 (a, b), GmAP1d, and GmLFY1 were slightly down-regulated in ft3b plants, the floral inducers GmFT5a and GmFT5b were highly expressed, indicating potential compensation for the loss of GmFT3b. We suggest that GmFT3b acts redundantly in flowering time regulation and may be compensated by other FT homologs in soybean. [ABSTRACT FROM AUTHOR]

The flowering time of soybean is a highly important agronomic characteristic, which affects the adaptability and yield. AtMRF1 , a MORN-repeat motif gene, acts as a floral promoter in Arabidopsis , its functions in soybean are not yet understood. Here, we employed qRT-PCR to analyze the tissue expression patten of MRF1 homologs in soybean and determined that the GmMRF2 gene, containing a MORN-motif, highly expressed in the shoot and responded to photoperiod. GmMRF2 overexpression soybean lines exhibited earlier flowering time under long-day (LD) conditions, and increased plant height under both LD and short-day (SD) conditions compared to wild-type (WT) plants. The expression levels of gibberellic acid (GA) pathway genes that positively regulate plant height genes and flowering-promoting genes were up-regulated in the GmMRF2 overexpression lines, were up-regulated in the GmMRF2 overexpression lines. Further study revealed that Gm MRF2 interacted with GmTCP15 to co-induce the expression of GmSOC1b. Together, our results preliminarily reveal the functions and mechanisms of GmMRF2 in regulating flowering time and plant height, provide a new promising gene for soybean crop improvement. • GmMRF2 overexpression promoted flowering and increased plant height in soybean. • The expression level of GA pathway and flowering related genes was alerted in the GmMRF2 overexpression lines. • GmMRF2 interacted with GmTCP15 to co-induce the expression of GmSOC1b to accelerate soybean flowering. [ABSTRACT FROM AUTHOR]