GmDFB1, an ARM-repeat Superfamily Protein, Regulates Floral Organ Identity Through Repressing Sirna- and Mirna-Mediated Gene Silencing in Soybean

The development of flowers in soybean (Glycine max) is essential for determining the yield potential of the plant. Gene silencing pathways are involved in modulating flower development, but their full elucidation is still incomplete. Here, we conducted a forward genetic screen and identified an abnormal flower mutant, deformed floral bud1-1 (Gmdfb1-1), in soybean. We mapped and identified the causal gene, which encodes a member of the armadillo (ARM)-repeat superfamily. Using small RNA sequencing (sRNA-seq), we found an abnormal accumulation of small interfering RNAs (siRNAs) and microRNA (miRNAs) in the Gmdfb1 mutants. We further demonstrated that GmDFB1 interacts with the RNA exosome cofactor SUPER KILLER7 (GmSKI7). Additionally, GmDFB1 interacts with the PIWI domain of ARGONAUTE 1 (GmAGO1) to inhibit the cleavage efficiency on the target genes of sRNAs. The enhanced gene silencing mediated by siRNA and miRNA in the Gmdfb1 mutants leads to the downregulation of their target genes associated with flower development. This study revealed the crucial role of GmDFB1 in regulating floral organ identity in soybean probably by participating in two distinct gene silencing pathways.