Accepts the ubiquitin-like protein NEDD8/RUB1 from the ECR1-AXR1 E1 complex and catalyzes its covalent attachment to other proteins. Protein modification; protein neddylation. Interacts with RBX1. Expressed in shoot, root and floral meristems, and in vascular tissues of leaves. Reduction in RCE1 levels leads to reduced organ length and defects in gravitropism. May be due to intron retention. Belongs to the ubiquitin-conjugating enzyme family. UBC12 subfamily.