# Chemical Genetics with SP600125 Reveals That Mps1 Protein Kinase Works as a Regulatory Element in Post-embryonic Development of the Arabidopsis thaliana Root SystemAn Insight into Plant Cell Cycle Control

## TL;DR

This study shows that the Mps1 protein kinase, known for its role in cell division, is important for root development in Arabidopsis and can be inhibited by SP600125.

## Contribution

The study reveals that Mps1 functions in post-embryonic plant development and is inhibited similarly in plants and humans by SP600125.

## Key findings

- Arabidopsis Mps1 has a catalytic structure similar to human Mps1.
- SP600125 inhibits Mps1 activity and affects postgerminative development in Arabidopsis.
- Mps1 activity is essential for cell proliferation and development in plants.

## Abstract

The “spindle assembly checkpoint” (SAC)
is a regulatory
pathway that monitors the correct anchoring of the mitotic spindle
microtubules to chromosomes during the metaphase–anaphase transition.
The protein kinase monopolar spindle 1 (Mps1) is a key SAC component
and is considered a promising target for antitumor drugs. This has
led to the development of different inhibitory molecules that have
helped to elucidate the Mps1 functions in the cell cycle. However,
in plants, the catalytic mechanisms and roles of Mps1 during cell
proliferation remain unknown. Here, we show that Arabidopsis
thaliana’s Mps1 (AtMps1) has a similar catalytic
structure to that observed in humans (Homo sapiens’ Mps1HsMps1) and that its inhibition by SP600125
hinders postgerminative development. Further, our computational docking
studies strongly suggest that both HsMps1 and AtMps1 interact with
SP600125 in a similar manner and that plant proteins have topologically
conserved protein–protein interaction motifs in their kinase
domains. Furthermore, using A. thaliana as an experimental model demonstrates that Mps1 activity is essential
for cell proliferation and postgerminative development and that SP600125
effects are reversible. Our experiments open new possibilities for
understanding the mechanisms of the Mps1 protein using plants as experimental
models. They also show that chemical genetics is a robust alternative
for studies of plant development.