# Genome-Wide Characterization of the PbeDof Gene Family Reveals PbeDof9.1 as a Key Regulator of Salt Tolerance via Enhancing Antioxidant Capacity in Pyrus betulifolia

## TL;DR

This study identifies a gene, PbeDof9.1, in Pyrus betulifolia that helps plants tolerate salt stress by improving antioxidant defenses.

## Contribution

The study reveals PbeDof9.1 as a novel key regulator of salt tolerance in pear rootstocks through enhanced antioxidant capacity.

## Key findings

- PbeDof9.1 is strongly induced by salt stress and is predominantly expressed in roots.
- Overexpression of PbeDof9.1 in Arabidopsis improves root system architecture under salt stress.
- PbeDof9.1 reduces oxidative damage by increasing antioxidant enzyme activities in pear calli.

## Abstract

Soil salinization severely restricts the sustainable development of the pear industry. Pyrus betulifolia, a vital native salt-tolerant rootstock in China, holds great significance for investigating stress resistance mechanisms. Plant-specific DNA-binding One Zinc Finger (Dof) transcription factors act as pivotal regulators in stress adaptation. However, their functions in P. betulifolia remain largely unexplored. In this study, we identified 43 PbeDof members within the P. betulifolia genome and classified them into eight subfamilies via phylogenetic analysis. Gene structure and conserved motif analyses revealed that PbeDof members within the same subfamily share similar exon-intron organizations and protein architecture, suggesting evolutionary conservation. Promoter analysis indicated that PbeDof genes are rich in cis-acting elements related to light, phytohormones (especially ABA and MeJA), and stress responses, implying their potential roles in diverse biological processes. Chromosomal localization and collinearity analyses revealed that segmental duplication was the primary driver of this family’s expansion. Combined transcriptomic profiling and qRT-PCR assays demonstrated that PbeDof9.1 is predominantly expressed in roots and is strongly induced by salt stress. Subcellular localization confirmed that PbeDof9.1 targets the nucleus. Functional characterization indicated that heterologous overexpression of PbeDof9.1 in Arabidopsis thaliana significantly enhances salt tolerance at germination and seedling stages. Notably, under 175 mM NaCl stress, the transgenic lines exhibited a superior root system architecture, with primary root length and lateral root numbers being approximately 1.5-fold higher than those of the wild type. Furthermore, homologous overexpression in pear calli confirmed that PbeDof9.1 mitigates oxidative damage by boosting the activities of peroxidase (POD) and catalase (CAT) to scavenge reactive oxygen species (ROS), thereby reducing malondialdehyde (MDA) accumulation. Collectively, this study characterizes the PbeDof family and establishes PbeDof9.1 as a key candidate gene for the genetic improvement of salt tolerance in pear rootstocks.