# Genome-wide analysis of DC1 domain proteins in Ipomoea species reveals IbCHR10 as a positive regulator of salt tolerance in sweet potato

## TL;DR

This study identifies IbCHR10 as a gene that helps sweet potato tolerate salt stress, offering a potential tool for breeding more resilient crops.

## Contribution

The study identifies IbCHR10 as a novel positive regulator of salt tolerance in sweet potato through genome-wide and functional analyses.

## Key findings

- Twelve CHR genes were identified in I. batatas and I. triloba, with conserved structures and syntenic relationships.
- IbCHR10 was strongly induced by salt stress and its overexpression improved salt tolerance in sweet potato.
- Overexpression of IbCHR10 reduced oxidative damage and increased antioxidant activity under salt stress.

## Abstract

Sweet potato (Ipomoea batatas (L.) Lam.) is an important food, feed, and industrial crop with high tolerance to marginal environments, yet its complex hexaploid genome limits molecular understanding of stress tolerance mechanisms. DC1 domain proteins, characterized by cysteine/histidine-rich (CHR) zinc-binding motifs, have been implicated in diverse regulatory processes in plants, but their evolutionary features and biological functions remain largely unknown in sweet potato.

We conducted a genome-wide analysis of the CHR gene family in cultivated sweet potato and its two diploid relatives, Ipomoea trifida and Ipomoea triloba, including phylogenetic, structural, synteny, promoter cis-element, and expression analyses (transcriptome and qRT-PCR). We further performed functional validation of a candidate gene by overexpression in sweet potato and assessed growth and physiological responses under salt stress.

Twelve CHR genes were identified in I. batatas and I. triloba, and eleven in I. trifida. These genes showed conserved gene structures, motif compositions, and syntenic relationships, with segmental duplication contributing to family expansion. Promoter analysis revealed abundant cis-acting elements related to hormone signaling and abiotic stress. Expression analyses demonstrated tissue-specific patterns and strong responses to salt, drought, ABA, and JA treatments. IbCHR10 was rapidly and strongly induced by salt stress, particularly in a salt-tolerant cultivar. Overexpression of IbCHR10 enhanced salt tolerance, evidenced by improved growth, reduced oxidative damage, increased antioxidant enzyme activity, enhanced osmotic adjustment, and elevated ABA and JA accumulation under salt stress.

This study provides a systematic characterization of DC1 domain (CHR) proteins in Ipomoea species and identifies IbCHR10 as an important regulator associated with salt stress tolerance, offering valuable genetic resources for developing stress-resilient sweet potato cultivars.