OTS1‐dependent deSUMOylation increases tolerance to high copper levels in Arabidopsis

Abstract

The conjugation of SUMO (small ubiquitin-like modifier) to protein substrates is a reversible process (SUMOylation/deSUMOylation) that regulates plant development and stress responses. The essential metal copper (Cu) is required for normal plant growth, but excess amounts are toxic. The SUMO E3 ligase, SIZ1, and SIZ1-mediated SUMOylation function in plant tolerance to excess Cu. It is unknown whether deSUMOylation also contributes to Cu tolerance in plants. Here, we report that OTS1, a protease that cleaves SUMO from its substrate proteins, participates in Cu tolerance in Arabidopsis thaliana (Arabidopsis). OTS1 loss-of-function mutants (ots1-2 and ots1-3) displayed increased sensitivity to excess Cu. Redox homeostasis and the balance between SUMOylation and deSUMOylation were disrupted in the ots1-3 mutant under excess Cu conditions. The ots1-3 mutant accumulated higher levels of Cu in both shoots and roots compared to wild type. Specific Cu-related metal transporter genes were upregulated due to the loss-of-function of OTS1, which might explain the high Cu levels in ots1-3. These results suggest that the SUMOylation/deSUMOylation machinery is activated in response to excess Cu, and modulates Cu homeostasis and tolerance by regulating both Cu uptake and detoxification. Together, our findings provide insight into the biological function and regulatory role of SUMOylation/deSUMOylation in plant tolerance to Cu.

Insights into the transcriptional and post-transcriptional regulation of the rice SUMOylation machinery and into the role of two rice SUMO proteases

“…The current view is that ESD4 proteins are important for development and flowering time, with the exception of AtELS1 (the only cytoplasmic member) whose KO only shows slightly reduced growth [35]; OsFUG1 KO also significantly impacts development and fertility (Fig. 7); the SPF-family proteins regulate embryo development [78], and the knockout shows late flowering, increased seed size and fertility defects [73]; the OTS family is involved in salt response [48], drought [47], and copper sensitivity [86].…”

Dealing With Stress: A Review of Plant SUMO Proteases

“…However, ots1-2 plants have a constantly high level of SUMOylated proteins that does not show much of a response to the high levels of copper. OTS1 was shown to function in copper uptake and distribution; in the ots1-2 mutant, more copper was detected in seedlings shoots and roots compared to WT; additionally, these knockout plants had greater expression of genes responding to high copper when placed on excess copper media than WT (Zhan et al, 2018).…”

OsMSR3, a Small Heat Shock Protein, Confers Enhanced Tolerance to Copper Stress in Arabidopsis thaliana

“…One of the earliest and most obvious symptoms of Cu stress is inhibition of primary root elongation [15,16,17], while its prominent manifestations are decreased proliferation of root meristem cells [18], impaired cell integrity [19], and cell death [20]. Excessive accumulation of Cu in plants leads to the production of reactive oxygen species (ROS), which are toxic owing to their high redox activity [21].…”