Comprehensive Analyses of the PfGRF Transcription Factor Family and Its Response to Biotic and Abiotic Stresses

Growth regulatory factor (GRF) genes play a crucial role in plant growth and development, reproduction, metabolism, and stress resistance. In this study, we conducted a genome-wide integrated analysis of transcriptome and miRNA expression profiles in Paulownia fortunei challenged by phytoplasma infection, with a specific focus on elucidating the functional landscape of the PfGRF transcription factor (TF) family. A comprehensive investigation was conducted on the PfGRF TF family. A total of 16 PfGRF genes were identified in this study, among which 13 were located on the chromosomes of P. fortunei. They were divided into six groups based on amino acid sequences. Notably, proteins within the same subgroup exhibited remarkable structural conservation, whereas significant inter-subgroup divergence was observed, suggesting functional specialization. Evolutionary expansion of the PfGRF family was primarily driven by segmental duplication events, highlighting a key mechanism underlying genetic redundancy and functional diversification in this lineage. Segmental duplication was the main mechanism of PfGRF family expansion. Cis-acting elements responsive to phytohormones and abiotic stresses were detected in the promoter regions of the PfGRFs. Yeast two-hybrid and bimolecular fluorescence complementation technology confirmed the interaction between PfGRF14 and PfGIPa. This work lays a foundation for future research into the functions of the PfGRF TF family, and provides a reference for studies of the mechanism of Paulownia Witches’ broom (PaWB) development.