Are Involved in the Regulation of Lignin Synthesis and Rapid Growth in .

(1) Background: Lignin is a unique component of the secondary cell wall, which provides structural support for perennial woody plants. are the core factors of the auxin-signaling pathway, which plays an important role in promoting plant growth, but the specific relationship between auxin response factors and lignin has not been fully elucidated with regard to rapid plant growth in forest trees. (2) Objectives: This study aimed to investigate the relationship between and lignin with regard to rapid plant growth in forest trees. (3) Methods: We used bioinformatics analysis to investigate the family, find genes homologous to and in , and explore the changes in gene expression and lignin content under light treatment. (4) Results: We identified and characterized 35 based on chromosome-level genome data from . In total, we identified 92 genes in , , and , which were subsequently divided into three subgroups based on phylogenetic analysis and classified the conserved exon-intron structures and motif compositions of the into the same subgroups. Collinearity analysis suggested that segmental duplication and whole-genome duplication events were majorly responsible for the expansion of the family, and the analysis of Ka/Ks indicated that the majority of the duplicated underwent purifying selection. The analysis of cis-acting elements showed that were sensitive to light, plant hormones, and stress. We analyzed the tissue-specific transcription profiles of with transcriptional activation function and the transcription profiles of with high expression under light in the stem. We also measured the lignin content under light treatment. The data showed that the lignin content was lower, and the gene transcription profiles were more limited under red light than under white light on days 1, 7, and 14 of the light treatments. The results suggest that may be involved in the regulation of lignin synthesis, thereby promoting the rapid growth of . (5) Conclusions: Collectively, this study firstly reports that may be involved in the regulation of lignin synthesis and in promoting the rapid growth in