# Treatments with Diquat Reveal the Relationship between Protein Phosphatases (PP2A) and Oxidative Stress during Mitosis in Arabidopsis thaliana Root Meristems

## TL;DR

This study explores how oxidative stress affects mitosis in plant root cells and shows that protein phosphatase PP2A plays a key role in responding to stress.

## Contribution

The study reveals a novel link between PP2A dysfunction and oxidative stress sensitivity during mitosis in Arabidopsis root meristems.

## Key findings

- PP2A mutants show increased sensitivity to oxidative stress during mitosis.
- Diquat treatment reduces mitotic activity and alters histone H3 phosphorylation in PP2A mutants.
- Phosphatase activity is reduced only in stronger PP2A mutant genotypes after diquat treatment.

## Abstract

Reversible protein phosphorylation regulates various cellular mechanisms in eukaryotes by altering the conformation, activity, localization, and stability of substrate proteins. In Arabidopsis thaliana root meristems, histone post-translational modifications are crucial for proper cell division, and they are also involved in oxidative stress signaling. To investigate the link between reactive oxygen species (ROS) and mitosis, we treated various Arabidopsis genotypes, including wild-types and mutants showing dysfunctional PP2A, with the ROS-inducing herbicide diquat (DQ). Studying the c3c4 double catalytic subunit mutant and fass regulatory subunit mutants of PP2A provided insights into phosphorylation-dependent mitotic processes. DQ treatment reduced mitotic activity in all genotypes and caused early mitotic arrest in PP2A mutants, likely due to oxidative stress-induced damage to essential mitotic processes. DQ had a minimal effect on reversible histone H3 phosphorylation in wild-type plants but significantly decreased phospho-histone H3 levels in PP2A mutants. Following drug treatment, the phosphatase activity decreased only in the stronger phenotype mutant plants (fass-5 and c3c4). Our findings demonstrate that (i) the studied PP2A loss-of-function mutants are more sensitive to increased intracellular ROS and (ii) DQ has indirect altering effects of mitotic activities and histone H3 phosphorylation. All these findings underscore the importance of PP2A in stress responses.