# ANAPHASE-PROMOTING COMPLEX/CYCLOSOME coactivators maintain AURORA 1 kinase homeostasis during meiotic chromosome segregation

## TL;DR

This study reveals how specific coactivators of the APC/C complex regulate Aurora 1 kinase levels during meiosis in plants.

## Contribution

The study identifies distinct roles of CDC20.1 and CCS52 coactivators in regulating Aurora 1 homeostasis during plant meiosis.

## Key findings

- APC/C ubiquitinates AUR1, leading to its degradation via the 26S proteasome pathway.
- CDC20.1 prevents AUR1 degradation, while CCS52A2/B promotes its ubiquitination and degradation.
- AUR1 levels and meiotic defects correlate with mutations in CDC20.1 and CCS52.

## Abstract

Faithful chromosome segregation is essential for both mitotic and meiotic cell division. The anaphase-promoting complex/cyclosome (APC/C) and its coactivators are required for meiotic chromosome segregation, but their potential targets and regulatory mechanisms remain unclear in plants. Here, we performed a ubiquitinome analysis and show that Arabidopsis thaliana Aurora 1 (AUR1) is over-ubiquitinated at lysine 102 in the coactivator Cell Division Cycle 20.1 (cdc20.1) mutants and that AUR1 overexpression can partially rescue the cdc20.1 meiotic defect. We also demonstrate that APC/C ubiquitinates AUR1, leading to its degradation through the 26S proteasome pathway. Moreover, the APC/C subunit and coactivators Cell Cycle Switch 52 A2/B (CCS52A2/B) and CDC20.1 interact with AUR1 both in vitro and in vivo. Intriguingly, CCS52A2/B promotes AUR1 ubiquitination and degradation, while CDC20.1 prevents AUR1 degradation. Consistent with this finding, AUR1 levels are lower in cdc20.1 and higher in ccs52 mutants relative to Col-0, and mutation of CCS52A2/B causes defects in meiotic spindle assembly and homologous chromosome segregation. Genetic analyses demonstrate that Arabidopsis anaphase-promoting complex/cyclosome subunit 8 (APC8), CDC20.1, CCS52 and AUR1 act in the same pathway to control meiotic spindle assembly and homologous chromosome segregation. Thus, this work provides mechanistic insight into the role of APC/C coactivators in regulating AUR1 homeostasis during meiosis in plants.

The ANAPHASE-PROMOTING COMPLEX/CYCLOSOME coactivators CDC20.1 and CCS52s play distinct roles in maintaining AURORA 1 kinase homeostasis during meiotic chromosome segregation in Arabidopsis.