Abstract: 【Objective】To provide more information for breeding, the gene Flowering Promoting Factor1-like Protein 5 (GhFLP5), a member of the flowering promoting factor family in Gossypium hirsutum L., was cloned, and then its expression patterns were studied to characterize its functions in flowering process. 【Method】According to the sequences on NCBI , specific primers were designed by Oligo7 and GhFLP5 was cloned from cDNA of cultivar CCRI50. The protein properties were predicted via ExPASy. FPFs of other species were retrieved from NCBI. ClustalX2 was used for multiple sequence alignment and phylogenetic tree was constructed by MEGA6. The samples of different stages and different tissues of early maturity variety CCRI50 and later maturity variety Lu28 were used to study the spatial and temporal expression profiles of GhFLP5. A 1 500 bp fragment upstream the start codon was taken from the genomic database, then the cis-acting elements were analysed with PlantCARE. Based on the predictions, several phytohormones were selected to explore the responses of GhFLP5. pBI121-GhFLP5, a recombinant expression plasmid was constructed and transformed into Arabidopsis. The homozygous overexpression lines were observed and expression profiles were performed with quantitative real-time PCR (qRT-PCR). 【Result】With a 300 bp coding frame, GhFLP5 encoded a 11.4 kD protein. There were three pretty conserved domains, which reveals that GhFLP5 has a close relationship with those of Glycine max, Medicago truncatula and Polulus trichocarpa. Spatial expression patterns showed that it expressed predominantly in leaves. And GhFLP5 was transcribed at a higher level in early maturity variety CCRI50 than in later maturity variety Lu28. Temporal expression patterns showed that it hit a peak at three-true-leaf stage in CCRI50 but at four-true-leaf stage in Lu28. There were mainly two kinds of cis-acting elements in promoter region: one was light-response elements and circadian elements, and the other was stress-response elements. According to the elements' distributions and functions, salicylic acid (SA), abscisic acid (ABA) and jasmonic acid (JA) were selected to treat cotton seedlings. As a result, GhFLP5 was activated by SA and ABA, while it was suppressed by JA. The overexpression plants bolted about 9 days and flowered about 7 days earlier than the wild type. Meanwhile, the rosette leaves decreased, and all the differences were extremely significant. Quantitative analysis showed that the genes promoting flowering such as LEAFY (AtLFY), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS (AtSOC1), FLOWERING LOCUS T (AtFT), APETALA1 (AtAP1)and FRUITFULL (AtFUL) were up-regulated in 35S::GhFLP5 lines, while the gene AtFLC, delaying flowering, was down-regulated. Moreover, the auxin-responsive genes SMALL AUXIN UPREGULATED 20 (AtSAUR20) and SMALL AUXIN UPREGULATED 22 (AtSAUR22) were induced in transgenic Arabidopsis lines. GIBBERELLIN 20-OXIDASE 1 (GA20OX1), a gene involved in gibberellin (GA) biosynthesis, was also up-regulated more than two folds. 【Conclusion】The Arabidopsis thaliana lines over-expressing GhFLP5 performed an obvious early-flowering phenotype. Moreover, the gene expression profiles indicated that GhFLP5 may play dual roles in the transition to flowering via both GA and IAA signaling pathways.

Key words: upland cotton, flowering time, GhFLP5, expression patterns, gene functions