Plasma membrane-association of SAUL1-type plant U-box armadillo repeat proteins is conserved in land plants

Abstract

Post-translational protein modification plays a pivotal role in the regulation and specific turnover of proteins. One of these important modifications is the ubiquitination of target proteins, which can occur at distinct cellular compartments. At the plasma membrane, ubiquitination regulates the internalization and thus trafficking of membrane proteins such as receptors and channels. The Arabidopsis plant U-box (PUB) armadillo repeat (PUB-ARM) ubiquitin ligase SAUL1 (SENESCENCE-ASSOCIATED UBIQUITIN LIGASE1) is part of the ubiquitination machinery at the plasma membrane. In contrast to most other PUB-ARM proteins, SAUL1 carries additional C-terminal ARM repeats responsible for plasma membrane-association. Here, we demonstrated that the C-terminal ARM repeat domain is also essential and sufficient to mediate plasma membrane-association of the closest Arabidopis paralog AtPUB43. We investigated targeting of PUB-ARM ubiquitin ligases of different plant species to find out whether plasma membrane-association of SAUL1-type PUB-ARM proteins is conserved. Phylogenetic analysis identified orthologs of SAUL1 in these plant species. Intracellular localization of transiently expressed GFP fusion proteins revealed that indeed plasma membrane-association due to additional C-terminal ARM repeats represents a conserved feature of SAUL1-type proteins. Analyses of transgenic Arabidopsis plants overexpressing N-terminally masked or truncated proteins revealed that interfering with the function of SAUL1-type proteins resulted in severe growth defects. Our results suggest an ancient origin of ubiquitination at the plasma membrane in the evolution of land plants.

NORE1/SAUL1 integrates temperature‐dependent defense programs involving SGT1b and PAD4 pathways and leaf senescence in Arabidopsis

“…The enhanced resistance was more pronounced in the saul1‐1/nore1‐2 , possibly because of the effect of allelic variation. It was previously known that ARM repeats in NORE1, which are responsible for protein–protein interaction, are critical for regulating premature senescence (Vogelmann et al ). The fact that nore1‐1 contains a missense mutation at the 665th threonine residue in ARM repeats further provides information on the importance of this residue in controlling defense and senescence processes.…”

Genome-Wide Survey and Expression Analysis of Chlamydomonas reinhardtii U-box E3 Ubiquitin Ligases (CrPUBs) Reveal a Functional Lipid Metabolism Module

“…reinhardtii [ 58 ]. The arm domain present in AtPUB and OsPUB is necessary for substrate conjugation during ubiquitination and plasma membrane association [ 59 ]. Arm repeat proteins also exist in C .…”

Semi-dwarf barley (Hordeum vulgare L.) brh2 and ari-l mutants are deficient in a U-box E3 ubiquitin ligase

“…Below the DNA sequence is the polypeptide sequence of 460 amino-acid residues. The postulated U-box domain and a domain with an armadillo-like fold are marked in light grey (amino-acid residues 65-139) and dark grey (171-440), respectively (Groves and Barford 1999;Hu et al 2013;Vogelmann et al 2014). (Du et al 2009;Smalle and Vierstra 2004).…”