GbFT, a FLOWERING LOCUS T homolog from Ginkgo biloba, promotes flowering in transgenic Arabidopsis

Abstract Ginkgo biloba has a long juvenile phase, that prevents efficient breeding and genetic improvement. The molecular mechanism underlying the transition from vegetative to reproductive phase is currently unknown in G. biloba . FLOWERING LOCUS T ( FT ) encodes a mobile signaling protein involved in regulating flowering and other aspects of plant development. Herein, a FT homolog ( GbFT ) was isolated and characterized from G. biloba . GbFT encodes a 1091 bp gene with a predicted protein of 173 amino acids. GbFT was specifically expressed in the male and female strobili of G. biloba . GbFT expression showed a pattern of circadian rhythm and daily oscillation. Overexpression of GbFT using the CaMV 35S promoter in transgenic Arabidopsis plants caused early flowering phenotype compared with wild-type (WT) plants, indicating that GbFT promotes flowering. RNA-seq analysis of GbFT transgenic Arabidopsis plants (GbFT-OE) and WT plants screened out 227 significant differentially expressed genes (DEGs). Of these DEGs, 23 flowering-related DEGs were up-regulated in GbFT-OE compared with WT plants. In addition, RNA-seq and qRT-PCR analysis results showed that ectopic overexpression of GbFT in Arabidopsis up-regulated other endogenous genes involved in flower organ development, transcription factors and ethylene pathway, which may explain early flowering phenotype in transgenic plants. Our results lay the foundation for clarifying the molecular regulatory mechanism of flowering and for developing methods to shorten the juvenile phase of G. biloba .