LEAFY1 and 2 are required for floral organ development in soybean

The transition from vegetative to reproductive growth is a vital step for the reproductive success of plants. In Arabidopsis thaliana, LEAFY (LFY) plays crucial roles in inflorescence primordium and floral organ development, but little is known about the roles of its homologs in crop plants such as soybean (Glycine max). Here, we investigated the expression patterns and functions of the two LFY genes (LFY1 and LFY2) in soybean. Both genes were predominantly expressed in unopened flowers and the shoot apical meristem, with LFY2 having the higher transcript abundance. In an in situ hybridization assay, LFY genes produced strong signals in the floral meristem. We next generated lfy1 and lfy2 knockout lines. The lfy2 mutants showed obvious changes in floral organ morphology, but the lfy1 mutants showed no obvious changes in floral organ morphology or pod development. The lfy1 lfy2 double mutants displayed more serious defects in floral organ development than lfy2, resulting in complete sterility. Gene expression analysis revealed differences in expression of the A-class APETALA (AP) genes AP1a and AP1b in the double mutant lines. These results suggest that LFY2 plays an important role in floral organ formation in soybean by regulating the expression of homeotic genes. Our findings increase the understanding of floral development, which could be useful for flower designs during hybrid soybean breeding.