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

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 <i>Gossypium hirsutum GRF</i> 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 <i>GRF</i> family genes varied greatly among different species, and they were categorized into four subfamilies (I-IV) according to their phylogenetic relationships. The <i>G. hirsutum GRF</i> 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 <i>GRF</i> genes expanded in <i>G. hirsutum</i> by segmental duplication. The promoter region of the <i>G. hirsutum GRF</i> 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 <i>G. hirsutum GRF</i> genes was significantly higher in leaves than in other tissues, and some <i>GRF</i> genes responded to a variety of abiotic stresses. Additionally, transcriptomic sequencing revealed significantly higher expression levels of <i>GhGRFs</i> (e.g., <i>GhGRF13/14/18</i>) in embryonic callus (EC) compared to non-embryonic callus (NEC). This differential expression was validated by RT-qPCR, which confirmed that <i>GhGRF13/14/16/20</i> were significantly upregulated in EC relative to NEC. These findings provide valuable candidate genes and molecular insights for improving <i>G. hirsutum</i> regeneration efficiency and yield-related traits through genetic manipulation, thereby accelerating the molecular breeding of elite <i>G. hirsutum</i> varieties.