Abstract
SummaryConjugation of the small ubiquitin‐related modifier (SUMO) to protein substrates has an impact on stress responses and on development. We analyzed the proteome and phosphoproteome of mutants in this pathway. The mutants chosen had defects in SUMO ligase SIZ1, which catalyzes attachment of single SUMO moieties onto substrates, and in ligases PIAL1 and PIAL2, which are known to form SUMO chains. A total of 2657 proteins and 550 phosphopeptides were identified and quantified. Approximately 40% of the proteins and 20% of the phosphopeptides showed differences in abundance in at least one of the analyzed genotypes, demonstrating the influence of SUMO conjugation on protein abundance and phosphorylation. The data show that PIAL1 and PIAL2 are integral parts of the SUMO conjugation system with an impact on stress response, and confirm the involvement of SIZ1 in plant defense. We find a high abundance of predicted SUMO attachment sites in phosphoproteins (70% versus 40% in the total proteome), suggesting convergence of phosphorylation and sumoylation signals onto a set of common targets.
Highlights
Post-translational modification (PTM) of proteins can cause changes in stability, activity, interaction or subcellular localization
Sumoylation is mediated by the heterodimeric small ubiquitin-related modifier (SUMO)-activating enzyme, by SUMO-conjugating enzyme (SCE1 in Arabidopsis) and by SUMO E3 and E4 ligases (SIZ1, HPY2, PIAL1 and PIAL2 in Arabidopsis) (Miura et al, 2005; Huang et al, 2009; Ishida et al, 2009; Tomanov et al, 2014)
Proteins were extracted from plant samples comprising the whole aerial part of Col-0 WT, pial1 pial2, siz1 and pial1 pial2 siz1 mutants
Summary
Post-translational modification (PTM) of proteins can cause changes in stability, activity, interaction or subcellular localization. Its reversible and highly dynamic occurrence is coordinated by protein kinases and phosphatases. Another PTM is sumoylation, the covalent attachment of small ubiquitin-related modifier (SUMO) protein to lysine (Lys) residues of target proteins (Novatchkova et al, 2004, 2012; Castro et al, 2012; Xu and Yang, 2013; Elrouby, 2015). Sumoylation is mediated by the heterodimeric SUMO-activating enzyme (subunits SAE1 and SAE2 in Arabidopsis), by SUMO-conjugating enzyme (SCE1 in Arabidopsis) and by SUMO E3 and E4 ligases (SIZ1, HPY2, PIAL1 and PIAL2 in Arabidopsis) (Miura et al, 2005; Huang et al, 2009; Ishida et al, 2009; Tomanov et al, 2014). Activated SUMO is transferred to SUMO-conjugating enzyme SCE, which can link SUMO to e-amino groups of Lys residues in the substrate. A typical sumoylation substrate carries a single SUMO moiety, but chains of SUMOs have been observed
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