Genome-Wide Identification and Characterization of the Growth-Regulating Factor Gene Family Responsive to Abiotic Stresses and Phytohormone Treatments in Populus ussuriensis

As a unique class of plant-specific transcription factors, the GROWTH-REGULATING FACTORs (GRFs) play pivotal roles in regulating plant growth, development, and stress responses. In this study, the woody plant <i>Populus ussuriensis</i> was taken as the research object. Nineteen <i>PuGRFs</i> were identified and classified into six clades, and their potential evolutionary relationships were analyzed. The possible biological functions of <i>PuGRFs</i> were speculated through bioinformatics analysis. Combining real-time fluorescence quantitative PCR, <i>PuGRFs</i> were determined to be actively expressed in young tissues, and there are distinct tissue-specific expressions in the mature tissues of woody plants. We also conducted RT-qPCR of PuGRFs under different abiotic stresses and phytohormone treatments, most of the family members were induced under the treatments of methyl jasmonate (MEJA) and salicylic acid (SA), and we also found that 4 of 19 PuGRFs might participate in abscisic acid (ABA)-mediated osmotic stress in roots. Protein-protein interaction prediction analysis showed that six <i>PuGRFs</i> can interact with two types of growth-regulating interaction factors (GIFs). Further prediction and verification revealed that <i>PuGRF1/2c</i> and <i>PuGRF1/2d</i>, which belong to the same clade and have highly similar sequences, exhibited divergent interaction capabilities with GIFs, indicating evolutionary fine-tuning and functional redundancy within the GRF family. These findings lay a foundation for studying the molecular mechanisms of <i>PuGRFs</i> in <i>P. ussuriensis</i>, suggest that <i>PuGRFs</i> play important roles in responding to hormones and environmental changes, and the potential interaction relationships are worthy of exploration.