Over-Expression of Soybean <i>Gm</i>SAUL1 Enhances Disease Resistance in <i>Nicotiana tabacum</i>

Abstract

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 GmSAUL1 (Senescence-Associated E3 Ubiquitin Ligase 1) homologs in soybeans. Ectopic over-expression of GmSAUL1a in Nicotiana tabacum 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 NtMPK6, but reduced activation of NtMPK4, responding to flg22 treatment, was observed in these GmSAUL1a-over-expressing tobacco lines, suggesting that over-expressing GmSAUL1a activates immune signaling through activating NtMPK6, but suppressing NtMPK4 kinase activity. Collectively, these results demonstrated that GmSAUL1 plays a positive and pivotal role in soybean immunity that is likely governed by NLR proteins.

Keywords

• E3 ligase
• <i>Glycine max</i>
• cell death
• immune responses
• MAPK