Background: Fully intrinsically disordered plant dehydrin ERD14 can protect enzymes via its chaperone-like activity, but it was not formally linked with enzymes of the plant redox system yet. This is of particular interest, as the level of H2O2 in Arabidopsis plants increases during osmotic stress, which can be counteracted by overexpression of ERD14.

Methods: The proteomic mass-spectrometry analysis of stressed plants was performed to find the candidates affected by ERD14. With cross-linking, microscale thermophoresis, and active-site titration kinetics, the interaction and influence of ERD14 on the function of two target proteins: glutathione transferase Phi9 and catalase was examined.

Results: Under osmotic stress, redox enzymes, specifically the glutathione transferase Phi enzymes, are upregulated. Using microscale thermophoresis, we showed that ERD14 directly interacts with GSTF9 with a KD of ~25 μM. ERD14 activates the inactive GSTF9 molecules, protects GSTF9 from oxidation, and can also increases the activity of the enzyme. Aside from GSTF9, we found that ERD14 can also interact with catalase, an important cellular H2O2 scavenging enzyme, with a KD of ~0.13 μM, and protects it from dehydration-induced loss of activity.

Conclusions: We propose that fully intrinsically disordered dehydrin ERD14 might protect and even activate redox enzymes, helping plants to survive oxidative stress under dehydration conditions.

General significance: ERD14 has a direct effect on the activity of redox enzymes.