RING finger protein RGLG1 and RGLG2 negatively modulate MAPKKK18 mediated drought stress tolerance in Arabidopsis

Abstract Mitogen activated protein kinase kinase kinase 18 (MAPKKK18) mediated signaling cascade plays important roles in Arabidopsis drought stress tolerance. However, the post‐translational modulation patterns of MAPKKK18 are not characterized. In this study, we found that the protein level of MAPKKK18 was tightly controlled by the 26S proteasome. Ubiquitin ligases RGLG1 and RGLG2 ubiquitinated MAPKKK18 at lysine residue K32 and K154, and promoted its degradation. Deletion of RGLG1 and RGLG2 stabilized MAPKKK18 and further enhanced the drought stress tolerance of MAPKKK18 ‐overexpression plants. Our data demonstrate that RGLG1 and RGLG2 negatively regulate MAPKKK18‐mediated drought stress tolerance in Arabidopsis .