# Systematic Analysis of the Maize CAD Gene Family and Identification of an Elite Drought-Tolerant Haplotype of ZmCAD6

## TL;DR

This study identifies a specific gene variant in maize that improves drought tolerance, offering a useful tool for breeding more resilient crops.

## Contribution

The first comprehensive analysis of the maize ZmCAD gene family and identification of a drought-tolerant ZmCAD6 haplotype.

## Key findings

- Nine ZmCAD genes were identified with distinct evolutionary and expression patterns.
- ZmCAD6 is strongly induced by drought stress and has a haplotype (H3) associated with improved drought tolerance.
- The ZmCAD6-H3 haplotype is proposed as a target for molecular breeding in maize.

## Abstract

Drought and salt stresses are major abiotic factors limiting maize yield. Lignin, a key cell wall component, plays a crucial role in boosting plant stress resistance. Cinnamyl alcohol dehydrogenase (CAD) is a vital enzyme at the late stage of lignin biosynthesis; however, a systematic study of its functions in abiotic stress responses and its potential for genetic improvement in maize remains lacking. In this study, we conducted the first comprehensive, multi-dimensional analysis of the maize ZmCAD gene family, including gene identification, evolutionary relationships, protein interaction networks, and stress-responsive expression patterns. We identified 9 ZmCAD members that showed significant functional divergence in evolution, structure, and expression patterns. Expression analysis revealed complex, tissue-specific responses of ZmCAD genes to drought and salt stress, with ZmCAD6 strongly induced by drought. Importantly, through haplotype analysis of 157 waxy maize inbred lines, we successfully identified an elite haplotype (H3) of ZmCAD6 that is significantly associated with improved drought tolerance in maize. This study not only clarifies the functional differentiation mechanisms of the ZmCAD gene family but also provides the identified elite ZmCAD6-H3 haplotype as a valuable genetic resource and precise target for molecular breeding aimed at enhancing drought tolerance in maize.