Genome-wide identification and expression pattern analysis of the TCP transcription factor family in Ginkgo biloba

Plant-specific TCP transcription factors play an essential role in plant growth and development. They can regulate leaf curvature, flower symmetry and the synthesis of secondary metabolites. The flavonoids in Ginkgo biloba leaf are one of the main medicinally bioactivate compounds, which have pharmacological and beneficial health effects for humans. In this study, a total of 13 TCP genes were identified in G. biloba, and 5 of them belonged to PCF subclades (GbTCP03, GbTCP07, GbTCP05, GbTCP13, GbTCP02) while others belonged to CIN (GbTCP01, GbTCP04, GbTCP06, GbTCP08, GbTCP09, GbTCP10, GbTCP11, GbTCP12) subclades according to phylogenetic analysis. Numerous cis-acting elements related to various biotic and abiotic signals were predicted on the promoters by cis-element analysis, suggesting that the expression of GbTCPs might be co-regulated by multiple signals. Transcript abundance analysis exhibited that most of GbTCPs responded to multiple phytohormones. Among them, the relative expression levels of GbTCP06, GbTCP11, and GbTCP13 were found to be significantly influenced by exogenous ABA, SA and MeJA application. In addition, a total of 126 miRNAs were predicted to target 9 TCPs (including GbTCP01, GbTCP02, GbTCP04, GbTCP05, GbTCP06, GbTCP08, GbTCP11, GbTCP12, GbTCP13). The correlation analysis between the expression level of GbTCPs and the flavonoid contents showed that GbTCP03, GbTCP04, GbTCP07 might involve in flavonoid biosynthesis in G. biloba. In short, this study mainly provided a theoretical foundation for better understanding the potential function of TCPs in G. biloba.