Isolation and functional characterization of a novel FLOWERING LOCUS T homolog (NtFT5) in Nicotiana tabacum

Abstract The phosphatidyl ethanolamine-binding proteins (PEBPs) function primarily in regulating flowering in plants. Here, we report a genome-wide identification of PEBPs and functional characterization of a novel FLOWERING LOCUS T homolog ( NtFT5 ) in tobacco, Nicotiana tabacum . Seven new PEBPs were identified by a genome-wide analysis from N. tabacum . Expression profile showed that NtFT5 was mainly expressed in flowers. Overexpression of NtFT5 conferred an early flowering phenotype. By optimizing rooting medium, heritable short life-cycle tobacco lines were obtained by overexpression of NtFT5. Several orthologs of flowering genes downstream of FT gene were up-regulated in the NtFT5 -overexpression transgenic plant lines. The NtFT5 -overexpressing tobaccos formed fewer flowers and seeds per capsule compared with wild type. The seed-to-seed life cycle of NtFT5 overexpressing tobacco lines was about 2.5 months. Gene identification was effectively undertaken in the short life-cycle tobacco line by a second transformation via a gusA reporter gene and transient expression of Ros1 via PVX (Potato Virus X)system. Our findings indicate that NtFT5 is a novel FT homolog that has potential to induce flowering, which will improve our understanding of the mechanism underlying flowering control in N. tabacum . In addition, the results show that the generated heritable short life-cycle transgenic tobacco line is an effective and stable host system to accelerate gene function study, which promises to provide a better tobacco research model for plants.