# Genome-Wide Identification and Expression Analysis of the GRF Gene Family in Gossypium hirsutum L

## TL;DR

This study identifies and analyzes GRF genes in cotton, finding they are important for growth and stress response, and could help improve cotton breeding.

## Contribution

The study provides a genome-wide identification and expression analysis of GRF genes in Gossypium hirsutum, revealing their roles in stress response and regeneration.

## Key findings

- 34 GRF genes were identified in G. hirsutum, distributed across 19 chromosomes and categorized into four subfamilies.
- GRF genes showed higher expression in leaves and embryonic callus, with some upregulated under abiotic stress.
- Promoter analysis revealed GRF genes contain stress response elements, suggesting roles in adversity tolerance.

## Abstract

Growth Regulating Factors (GRFs) are plant-specific transcription factors that play crucial roles in regulating growth and development throughout the plant life cycle. A total of 34 Gossypium hirsutum GRF family genes were identified at the genome-wide level, which were unevenly distributed on 19 chromosomes, and were predicted to be mainly localized in the nucleus and plasma membrane. The number of GRF family genes varied greatly among different species, and they were categorized into four subfamilies (I–IV) according to their phylogenetic relationships. The G. hirsutum GRF genes possessed specific highly conserved structural domains, Trp-Arg-Cys motif (WRC) and Gln, Leu, Gln motif (QLQ), and structural analysis of the genes revealed that they contained 1–23 exons, and most of them contained UTRs. Intraspecies covariance analysis revealed that the GRF genes expanded in G. hirsutum by segmental duplication. The promoter region of the G. hirsutum GRF gene contained a large number of adversity stress response elements, as well as a small number of hormone response elements and growth and development-related response elements. Transcriptome data showed that the expression of G. hirsutum GRF genes was significantly higher in leaves than in other tissues, and some GRF genes responded to a variety of abiotic stresses. Additionally, transcriptomic sequencing revealed significantly higher expression levels of GhGRFs (e.g., GhGRF13/14/18) in embryonic callus (EC) compared to non-embryonic callus (NEC). This differential expression was validated by RT-qPCR, which confirmed that GhGRF13/14/16/20 were significantly upregulated in EC relative to NEC. These findings provide valuable candidate genes and molecular insights for improving G. hirsutum regeneration efficiency and yield-related traits through genetic manipulation, thereby accelerating the molecular breeding of elite G. hirsutum varieties.