The ubiquitin-dependent Arg/N-degron pathway relates the stability of a substrate protein to the nature of its N-terminal amino acid residue or its biochemical modifications, with some N-terminal residues being recognized by specific E3 ubiquitin ligases, resulting in the ubiquitylation and degradation of the substrate protein. Work in the model plant Arabidopsis thaliana has shown that the Arg/N-degron pathway is a key regulator of plant responses to hypoxia, which can be either physiological or a stress in the context of waterlogging or submergence. The role of the Arg/N-degron pathway in hypoxia response is mediated via the oxygen-dependent degradation of group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factors, which act as the master regulators of the hypoxia response program in plants. Analysis of Arabidopsis mutants for different enzymatic components of the Arg/N-degron pathway has also revealed its roles in the regulation of responses to other abiotic stresses (e.g. salt stress), as well as to pathogens. Although much has been learned from studies in Arabidopsis about the functions of the Arg/N-degron pathway, very little is known about this pathway in crops, including in Brassica crops such as oilseed rape, cabbage or turnip. To determine functional similarities and divergence of the Arg/N-degron pathway between Arabidopsis and Brassica crops, we isolated and characterized the first Arg/N-degron pathway mutants in Brassica rapa (turnip, pak choi), a diploid Brassica crop closely related to oilseed rape. We focused on two enzymatic components, namely the arginine-transferases ( ATE s) and the E3 ubiquitin ligase PROTEOLYSIS6 ( PRT6 ). Our results show both similarities and divergence of function for these Arg/N-degron pathway components in B. rapa compared to Arabidopsis. Specifically, ATE mutants in B. rapa arrest their development at the seedling stage, which contrasts with the mild phenotypic defects of the equivalent Arabidopsis mutants. Double mutant lines for two of the three PRT6 genes in B. rapa indicated a constitutive activation of hypoxia response genes at the transcriptional level, as shown in the single prt6 mutant in Arabidopsis. However, contrary to Arabidopsis, the B. rapa double mutants were more sensitive to waterlogging and hypoxia, and did not show differential response to salt stress or to biotic stress compared to the wild type. The functional divergence identified likely reflects variability in each species in the substrate repertoire and/or in the regulation of pathways or targets downstream of Arg/N-degron pathway substrates. Such differences could be driven by direct selective pressures at N-termini (e.g. gain or loss of a destabilizing N-terminal residue), or by species-specific proteases that may generate destabilizing neo-N-termini after cleavage. These similarities and differences highlight the difficulties in translating research findings from Arabidopsis to crops, even within the same plant family (Brassicaceae) and highlight the need to study pathways in crops. ### Competing Interest Statement The authors have declared no competing interest. Science Foundation Ireland, https://ror.org/0271asj38, 13/IA/1870, 20/FFP-P/8433 Irish Research Council, https://ror.org/051xex213, GOIPG/2017/2

Protein biogenesis requires the ribosome to collaborate with a diverse set of cotranslational factors that shape the fate of nascent chains. These int…

Cells depend on early protein modifications for proper function. Here, the authors show that when Src-family signaling kinases lack their typical myristoylation, an alternative acetylated start is det...

NAC enables cotranslational N-terminal processing of histones H2A and H4 by recruiting MetAP1 and NatD at the ribosomal tunnel.

Huntingtin-interacting protein K (HYPK) promotes the activity of N-terminal acetyltransferase A (NatA), which cotranslationally acetylates 40% of the eukaryotic proteome. Kinetic and in-cell measurements revealed that HYPK acts as a ribosome exchange factor for NatA, enabling its access to and acetylation of the translatome.

Welcome to the lab website of Professor Daniel Gibbs @ University of Birmingham

Genome-wide CRISPR/Cas9 screening identifies the N-terminal acetyltransferase NAA60 to facilitate cis- and carboplatin drug sensitivity, most likely by neutralizing Nt acetylation of the LRRC8A/D VRAC subunits regulating substrate permeability.

In two recent papers in Cell, Zhu et al. and Luo et al. use selective ribosome profiling to identify the substrates and timing of co-translational protein targeting to mitochondria. The results sugges...