# The photolyase/cryptochrome of Aspergillus nidulans senses oxidative stress and shuttles from nuclei to mitochondria

## TL;DR

A fungal protein called CryA detects oxidative stress and moves from the nucleus to mitochondria, suggesting a new role in stress response.

## Contribution

The study reveals CryA's role in sensing oxidative stress and shuttling to mitochondria, a novel function for fungal cryptochrome-like photolyases.

## Key findings

- CryA translocates from nuclei to mitochondria within one minute of hydrogen peroxide exposure.
- CryA interacts with phytochrome and AtfA to regulate stress-activated genes through negative feedback loops.
- The N-terminal extension and a cysteine in CryA are essential for its mitochondrial translocation upon oxidation.

## Abstract

Cryptochromes are photoreceptors with functions in the entrainment of circadian clocks or as proposed magnetoreceptors in birds or as light-independent regulators of stress responses in plants. Here, we show that the fungal cryptochrome-like photolyase CryA from Aspergillus nidulans is induced by light and oxidative stress and establishes negative-feedback loops for light- and stress-activated genes. The negative-feedback loops depend on CryA interaction with phytochrome and the HOG (high osmolarity glycerol) pathway transcription factor AtfA in nuclei. CryA translocated in less than one minute from nuclei to mitochondria in the presence of hydrogen peroxide suggesting mitochondrial functions and possibly mitochondrial-nuclear communication. The shuttle to mitochondria depended on the N-terminal extension and a cysteine therein, which probably induces conformational changes of CryA upon oxidation. Therefore, we propose CryA as a sensor for oxidative stress. Such an N-terminal extension is also present in other photolyases and some cryptochromes, suggesting evolutionary conservation of the mechanism.

Fungal cryptochromes are photoreceptors that regulate DNA damage, cell development, and the circadian clock. Here, Landmark et al. show that a fungal cryptochrome-like photolyase regulates light- and stress-activated genes and relocates from nuclei to mitochondria in response to oxidative stress.