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E3 ubiquitin ligases play essential roles in plant defense responses. However, their roles in other plant species have not been investigated extensively. Here, we used a gain-of-function approach to interrogate the function of <i>Gm</i>SAUL1 (Senescence-Associated E3 Ubiquitin Ligase 1) homologs in soybeans. Ectopic over-expression of <i>GmSAUL1a</i> in <i>Nicotiana tabacum</i> resulted in autoimmune responses that could be suppressed by high temperature, which is a hallmark of NLR (nucleotide-binding leucine-rich repeat protein)-mediated resistance. Interestingly, an elevated activation of <i>Nt</i>MPK6, but reduced activation of <i>Nt</i>MPK4, responding to flg22 treatment, was observed in these <i>GmSAUL1a-</i>over-expressing tobacco lines, suggesting that over-expressing <i>GmSAUL1a</i> activates immune signaling through activating <i>Nt</i>MPK6, but suppressing <i>Nt</i>MPK4 kinase activity. Collectively, these results demonstrated that <i>Gm</i>SAUL1 plays a positive and pivotal role in soybean immunity that is likely governed by NLR proteins.