Genome-Wide Identification of the TCP Gene Family in Broussonetia papyrifera and Functional Analysis of BpTCP8, 14 and 19 in Shoot Branching

The plant-specific TCP family proteins play an important role in the processes of plant growth and development. Broussonetia papyrifera is a versatile perennial deciduous tree, and its genome data have been published. However, no comprehensive analysis of the TCP gene family in B. papyrifera has been undertaken. In this study, 20 BpTCP genes (BpTCPs) were identified in the B. papyrifera genome. Phylogenetic analysis divided BpTCPs into three subclades, the PCF subclade, the CIN subclade and the CYC/TB1 subclade. Gene structure analysis displayed that all BpTCPs except BpTCP19 contained one coding region. Conserved motif analysis showed that BpTCP proteins in the same subclade possessed similar motif structures. Segmental duplication was the primary driving force for the expansion of BpTCPs. Expression patterns showed that BpTCPs may play diverse biological functions in organ or tissue development. Transcriptional activation activity analysis of BpTCP8, BpTCP14 and BpTCP19 showed that they possessed transcriptional activation ability. The ectopic expression analysis in Arabidopsis wild-type and AtBRC1 ortholog mutant showed that BpTCP8, BpTCP14 and BpTCP19 could prevent rosette branch outgrowth. Collectively, our study not only established the first genome-wide analysis of the B. papyrifera TCP gene family, but also provided valuable information for understanding the function of BpTCPs in shoot branching.