# Arabidopsis thaliana FANCONI ANAEMIA I (FANCI) has roles in the repair of interstrand crosslinks and CRISPR‐Cas9 induced DNA double strand breaks

## TL;DR

This study shows that the FANCI protein in Arabidopsis helps repair DNA damage, including crosslinks and CRISPR-induced breaks, which is important for plant survival.

## Contribution

The study reveals new roles of FANCI in plant DNA repair, including its involvement in CRISPR-induced double strand break repair.

## Key findings

- FANCI forms a complex with FANCD2 in plant cells, similar to mammals.
- FANCI is important for repairing DNA crosslinks and influences CRISPR-induced break repair patterns.
- FANCI mutations combined with MUS81 mutations increase programmed cell death in plants.

## Abstract

DNA repair is crucial for genome stability, in particular for plants which are exposed to high levels of damage arising from UV irradiation, soil pollutants and reactive oxygen species. Damage that affects both strands of the DNA duplex is harder to repair due to both the lack of a template strand and the potential for physical separation of fragmented chromosomes. As such, DNA double‐strand breaks (DSBs) and interstrand DNA crosslinks (ICL) are particularly cytotoxic forms of damage. Here we report the functions of FANCONI ANAEMIA I (FANCI), an Arabidopsis thaliana homologue of the mammalian ICL repair protein. We show that in plant cells, as in mammals, FANCI forms a nuclear localised complex with FANCD2. Genetic analysis of plants lacking FANCI displays significant hypersensitivity to the DNA crosslinking reagent mitomycin C. Furthermore, mutation of FANCI in combination with mutations in a second ICL repair factor, METHYL METHANESULFONATE AND UV‐SENSITIVE PROTEIN 81 (MUS81), results in increased levels of programmed cell death compared to the corresponding single mutants, revealing roles in maintaining plant genome stability. Sequence analysis of mutational repair of CRISPR‐Cas9‐induced DSBs revealed that FANCI promotes single nucleotide insertions and reduces longer deletions. This pattern of mutations may reflect roles for FA proteins in replication‐coupled repair of a subset of DSBs. Taken together, this analysis finds evidence for multiple roles for FANCI in the maintenance of plant genome stability.

DNA repair is essential for plant growth and development. However, the pathways for interstrand DNA crosslink (ICL) repair are not fully characterised in plants. Here we report that a factor important for ICL repair in mammals has similar functions in plants but finds additional roles influencing the repair of DNA double strand breaks. These findings advance our understanding of plant DNA damage responses, important for crop yields and plant survival under changing climates.