# Antarctic Microalga Chlamydomonas sp. ICE-L Cryptochrome CiCRY-DASH1 Mediates Efficient DNA Photorepair of UV-Induced Cyclobutane Pyrimidine Dimer and 6-4 Photoproducts

## TL;DR

This study identifies a cryptochrome in Antarctic microalgae that efficiently repairs UV-induced DNA damage, offering potential for biotech applications.

## Contribution

The discovery of CiCRY-DASH1's role in DNA photorepair and its engineered variants for biomanufacturing is novel.

## Key findings

- CiCRY-DASH1 repairs UV-induced CPD and 6-4PPs both in vivo and in vitro.
- The C-terminal loop region is crucial for photorepair activity.
- Engineered variants show high catalytic efficiency and evolutionary robustness.

## Abstract

Cryptochromes (CRYs) are a conserved class of blue light and near-ultraviolet light receptors that regulate diverse processes, including photomorphogenesis in plants. In the extreme Antarctic environment, ice algae endure intense UV radiation, prolonged darkness, and low temperatures, where cryptochromes play a vital role in light sensing and stress response. In this study, we cloned the complete open reading frame (ORF) of the cryptochrome gene CiCRY-DASH1 from the Antarctic microalga Chlamydomonas sp. ICE-L. Both in vivo and in vitro DNA photorepair assays showed that CiCRY-DASH1 effectively repairs cyclobutane pyrimidine dimer (CPD) and 6-4 photoproducts (6-4PPs) induced by UV radiation. Furthermore, deletion of the N-terminal and C-terminal loop regions, combined with activity assays, revealed that the C-terminal loop region plays a crucial role in photorepair activity. These findings elucidate the adaptive photorepair mechanisms of Antarctic microalgae and establish CiCRY-DASH1 as a valuable genetic resource. Specifically, the high catalytic efficiency and evolutionary robustness of the engineered variants position it as a promising marine bioactive agent for photoprotective therapeutics and a strategic target for constructing microbial chassis to enable sustainable drug biomanufacturing.