Cloning And Function Identification Of AfSBP7 From Aechmea Fasciata

The Bromeliaceae family consists of important tropical fruit (Ananas comosus) and tropical ornamental flowers. Interestingly, the flowering induction of bromeliads by ethylene is used widespread, but the precise mechanism of it remains unknown. Aechmea fasciata, also called Pink Pineapple, is a kind of popular ornamental plants. Compared to other bromeliads, the time from vegetative growth to reproductive period of A. fasciata is relatively shorter. As a result, A. fasciata is a good candidate to investigate the flowering mechanism of bromeliads.Base on the analysis of transcriptional data, we isolated a SQUAMOSA Promoter-binding Protein-like (SPL) homolog gene, AfSBP7, from A. fasciata by using rapid amplification of cDNA ends (RACE) technology. The full cDNA length ofî–‡fSBP7 is 2438 bp, which has an open reading frame with 1194 bp length and the deduced protein of it has 398 amino acid residues. AfSBP7 has a conserved SBP domain and has the highest similarity with Arabidopsis AtSPL9 and AtSPL15.AtSPL9 and AtSPL15 mainly regulate flowering time and leaf morphogenesis. As a result, we speculated that AfSBP7 might have similar function with them.Tissue specific expression analysis of AfSBP7 using quantitative real-time PCR (qRT-PCR) shows that it has the highest expression level in adult plants prior to flowering. The expression of AfSBP7 transcripts exhibited a peak at 20:00, indicating that AfSBP7 expression responded to the natural daily light rhythm. Besides, the AfSBP7 transcripts showed a rapid increase in central leaves treated with ethylene after 6 h, indicating its response to exogenous ethylene treatment.Yeast one-hybrid experiments verify AfSBP7 has the transcriptional activation domain.In order to identify the function of AfSBP7, we constructed the CaMV35S:AfSBP7 overexpression vector and transformed it into Arabidopsis Col-0 plants by agrobacterium-mediated method. The positive Arabidopsis T2 transgenic lines were identified by RT-PCR. It was observed that the T3 transgenic plants exhibited early flowering phenotype both in short-day and long-day conditions.In this study, we provided the first report of the isolation and functional characterization of AfSBP7, one of SPL gene family members in A. fasciata. These results all support that AfSBP7, a transactivition factor, may play a pivotal role in regulating flowering time in Arabidopsis.