From start to finish: amino-terminal protein modifications as degradation signals in plants

The amino- (N-) terminus (Nt) of a protein can undergo a diverse array of co- andposttranslational modifications. Many of these create degradation signals (N-degrons) thatmediate protein destruction via the N-end rule pathway of ubiquitin-mediated proteolysis. Inplants, the N-end rule pathway has emerged as a major system for regulated control of proteinstability. Nt-arginylation-dependent degradation regulates multiple growth, development andstress responses, and recently identified functions of Nt-acetylation can also be linked to effectson the in vivo half-lives of Nt-acetylated proteins. There is also increasing evidence that N-termini could act as important protein stability determinants in plastids. Here we review recentadvances in our understanding of the relationship between the nature of protein N-termini, Nt-processing events and proteolysis in plants.