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.

植物特异性TCP转录因子（TCP transcription factors）在植物生长发育过程中发挥至关重要的作用，可调控叶片卷曲、花对称性以及次生代谢产物的合成。银杏叶中的类黄酮（flavonoids）是一类主要的药用生物活性化合物，对人体具有药理学活性与健康裨益。本研究共从银杏（G. biloba）中鉴定得到13个TCP基因，经系统发育分析（phylogenetic analysis），其中5个归属于PCF进化枝（GbTCP03、GbTCP07、GbTCP05、GbTCP13、GbTCP02），剩余8个归属于CIN进化枝（GbTCP01、GbTCP04、GbTCP06、GbTCP08、GbTCP09、GbTCP10、GbTCP11、GbTCP12）。通过顺式元件分析（cis-element analysis），研究人员在这些基因的启动子区域预测到大量与各类生物、非生物信号相关的顺式作用元件（cis-acting elements），提示GbTCP基因的表达可能受多种信号协同调控。转录丰度（transcript abundance）分析结果显示，多数GbTCP基因可响应多种植物激素（phytohormones）；其中，GbTCP06、GbTCP11与GbTCP13的相对表达水平可显著受外源施加的脱落酸（Abscisic acid, ABA）、水杨酸（Salicylic acid, SA）及茉莉酸甲酯（Methyl jasmonate, MeJA）调控。此外，本研究共预测到126个微小RNA（miRNA）靶向调控9个TCP基因，涵盖GbTCP01、GbTCP02、GbTCP04、GbTCP05、GbTCP06、GbTCP08、GbTCP11、GbTCP12、GbTCP13。对GbTCP基因表达水平与类黄酮含量的相关性分析表明，GbTCP03、GbTCP04、GbTCP07可能参与银杏的类黄酮生物合成途径。综上，本研究为深入理解TCP转录因子在银杏中的潜在功能提供了坚实的理论基础。