# Genome-Wide Identification of GRAS Gene Family in Daylily (Hemerocallis citrina Baroni) and Its Expression Profiles in Development, Hormone and Biotic Stress Response

## TL;DR

This study identifies 78 GRAS genes in daylily and explores their roles in development, hormone response, and biotic stress adaptation.

## Contribution

The first comprehensive analysis of the GRAS gene family in Hemerocallis citrina, revealing its roles in development and stress response.

## Key findings

- 78 HcGRAS genes were identified and classified into 15 subfamilies based on chromosomal location and gene structure.
- HcGRAS genes are involved in organ development, hormone response, and defense against rust and thrips.
- HcGRAS38 interacts with SHR, SCR, and DELLA subfamily members, suggesting a central role in stress and developmental signaling.

## Abstract

This study examines the GRAS gene family in daylily, focusing on its role in flower development, hormone response and biotic stress. A total of 78 HcGRAS genes were identified and divided into 15 subfamilies. These genes encode basic, hydrophilic, unstable nuclear proteins and are distributed across 11 chromosomes, with segmental duplication driving their expansion. The transcriptome data and RT-PCR indicate that these genes are involved in organ development, hormone response, and rust and thrips response. These findings lay the groundwork for future research on the regulatory mechanisms of HcGRASs in development and response to biotic stress.

The family of GRAS transcription factors plays an essential role in the regulation of plant development, the transmission of hormonal signals, and the adaptation to environmental stresses seen in numerous species. However, a comprehensive analysis of the GRAS family of Hemerocallis citrina (daylily) is lacking, despite its potential to help understand the stress content and developmental processes of the monospecies. This study identified 78 GRAS genes (HcGRAS) in H. citrina, which were classified into 15 subfamilies based on chromosomal location, gene structure, conserved motifs, and expression patterns. An analysis of promoter regions indicated a significant presence of elements related to hormones and stress, showcasing these genes’ role in adapting to environmental pressures. The GO and KEGG analyses indicated that HcGRAS genes were engaged in pathways associated with developmental processes and responses to environmental stress. Notably, HcGRAS38 was identified as a key interacting protein for SHR, SCR, and DELLA subfamily members, which suggested its central role in coordinating stress response and developmental signaling. Comparative genomic mapping with seven representative monocot and dicot species underscored evolutionary conservation and divergence in functions of the GRAS family. The expression profiling of 22 HcGRAS genes across different daylily tissues provided insights into their tissue-specific roles. This research may promote the further exploration of the functional characteristics of HcGRAS genes.