Genome-Wide Identification of the TCP Gene Family and Preliminary Functional Investigation of HrTCP12 in Hippophae rhamnoides
WANG Ting, QIN Debin, AN Xinmin*
Sea buckthorn (Hippophae rhamnoides L.), as an important plant of medicinal and food origin, its fruits are highly utilised in several fields. In recent years, the improvement of branching of economic tree species is an important way to increase its fruit yield. While the TCP gene family has a key role in regulating growth and development and response to adversity, its family members have important roles in plant meristem development. In this study, the TCP gene family in sea buckthorn was systematically identified and its functional properties were resolved through bioinformatics combined with experimental validation. In this study, 29 TCP genes were identified in sea buckthorn based on genomic data. Phylogenetic analysis classified them into Class I (PCF subfamily) and Class II (CYC/TB1 and CIN subfamilies). Notably, the TCP domain’s basic region in Class II contained four additional conserved amino acids compared to Class I. Chromosomal localisation showed that the family members were unevenly distributed on chromosomes, and physicochemical analyses showed that most of the proteins of the sea buckthorn TCP family were hydrophilic and localised in the nucleus. Promoter analysis revealed that the promoters of the family members were enriched in light-responsive, hormone (e.g., ABA) and stress-related cis-elements, suggesting their involvement in multiple regulatory networks. Covariance analysis revealed extensive evolutionary conservation of the sea buckthorn TCP genes with Arabidopsis thaliana and date, and the family expansion was dominated by trans-chromosomal duplications driven by whole-genome duplication/segmental duplication. Tissuespecific expression showed that the CYC/TB1 subfamily gene HrTCP12 was highly expressed in thorns and lateral shoots, with lower expression in the rest of the site, implying its function in regulating meristem development. Subcellular localisation confirmed that HrTCP12 and HrTCP18 were predominantly localised in the nucleus, consistent with transcription factor identity. Overexpression of HrTCP12 in 84k poplar significantly inhibited the expression of the active genes PagWUS1/2 in the meristematic tissue of poplar, which preliminarily verified its conserved mechanism of regulating plant meristems by inhibiting lateral shoot growth. In this study, TCP gene family in sea buckthorn was identified at a genome-wide scale and the expression patterns of the CYC/TB1 subfamily genes were analysed. It was found that their members exhibit obvious tissue-specific expression characteristics. Additionally, HrTCP12 was found to inhibit the expression of active genes in the meristematic tissue of poplar, offering candidate genes for the improvement of meristematic characteristics in sea buckthorn using genetic approaches.
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