Identification and Expression Analysis of TCP Transcription Factors Under Abiotic Stress in Phoebe bournei

The <i>TCP</i> gene family encodes plant transcription factors crucial for regulating growth and development. While <i>TCP</i> genes have been identified in various species, they have not been studied in <i>Phoebe bournei</i> (Hemsl.). This study identified 29 <i>TCP</i> genes in the <i>P. bournei</i> genome, categorizing them into Class I (PCF) and Class II (CYC/TB1 and CIN). We conducted analyses on the <i>PbTCP</i> gene at both the protein level (physicochemical properties) and the gene sequence level (subcellular localization, chromosomal distribution, phylogenetic relationships, conserved motifs, and gene structure). Most <i>P. bournei TCP</i> genes are localized in the nucleus, except <i>PbTCP9</i> in the mitochondria and <i>PbTCP8</i> in both the chloroplast and nucleus. Chromosomal mapping showed 29 <i>TCP</i> genes unevenly distributed across 10 chromosomes, except chromosome 8 and 9. We also analyzed the promoter cis-regulatory elements, which are mainly involved in plant growth and development and hormone responses. Notably, most <i>PbTCP</i> transcription factors respond highly to light. Further analysis revealed three subfamily genes expressed in five <i>P. bournei</i> tissues: leaves, root bark, root xylem, stem xylem, and stem bark, with predominant <i>PCF</i> genes. Using qRT-PCR, we examined six representative genes-<i>PbTCP16</i>, <i>PbTCP23</i>, <i>PbTCP7</i>, <i>PbTCP29</i>, <i>PbTCP14</i>, and <i>PbTCP15</i>-under stress conditions such as high temperature, drought, light exposure, and dark. <i>PbTCP14</i> and <i>PbTCP15</i> showed significantly higher expression under heat, drought, light and dark stress. We hypothesize that <i>TCP</i> transcription factors play a key role in growth under varying light conditions, possibly mediated by auxin hormones. This work provides insights into the <i>TCP</i> gene family's functional characteristics and stress resistance regulation in <i>P. bournei</i>.