# Phylogenomic Reconstruction and Functional Divergence of the PARP Gene Family Illuminate Its Role in Plant Terrestrialization

## TL;DR

This study explores how the PARP gene family evolved in plants to help them adapt to life on land by improving DNA repair and stress responses.

## Contribution

The study reveals the early evolutionary origins and functional diversification of the PARP gene family in plants.

## Key findings

- PARP evolution began during the bryophyte radiation, expanding into three subfamilies from a single algal gene.
- Structural innovations in DNA-binding domains and transcriptional rewiring enabled PARPs to respond to terrestrial stressors.
- Functional analysis shows PARP proteins in Syntrichia caninervis protect against UV, heat, and genotoxic agents.

## Abstract

The evolution of robust DNA repair mechanisms was a prerequisite for the conquest of land by plants, a transition that exposed them to harsh new environmental stressors. The poly (ADP-ribose) polymerase (PARP) family is central to this adaptation, as it orchestrates DNA repair and stress signaling pathways essential for coping with the elevated UV radiation and desiccation of terrestrial environments. Yet its early evolutionary origins are unknown. Here, we present a comprehensive reconstruction of the PARP family’s history across the plant kingdom. Our phylogenomic analysis reveals that PARP evolution ignited during the bryophyte radiation, expanding from a single ancestral algal gene into three distinct subfamilies (PARP1, PARP2, and PARP3). This diversification was driven by structural innovations in DNA-binding domains and a rewiring of transcriptional networks to respond to terrestrial challenges. We provide direct experimental support for this hypothesis through functional analysis of PARPs from the extremotolerant moss Syntrichia caninervis. We show that its PARP proteins provide multifaceted protection against UV radiation, heat, and genotoxic agents, and that recently duplicated PARP2 genes are already diverging in function. Our work pinpoints the molecular adaptations in a key DNA repair family that enabled the greening of Earth and uncovers novel genetic targets for enhancing crop resilience.