Cloning And Charaterization Of Transcription Factor Gene CmbHLH1from Chrysanthemum Morifolium

Chrysanthemum（Chrysanthemum morifolium） is one of the ten most famous flowers in China, holding a major share of the cut flower and flowering pot plant market worldwide because of its valuable ornamental character. The growth and development of chrysanthemum as evoluted dicotyledonous, regulated by plenty of transcription factors, must be more complicated and sophisticated than others. bHLH transcription factor, named after its specific HLH domain, controls many prosesses including ion intake, photomorphogenesis, abiotic stress response et al. and has important functions in cell. Here we report a bHLH transcription fator gene called CmbHLHl, which regulates the absorption of irons. The main results are as follows:In this study, a full length cDNA of bHLH transcription fator gene called CmbHLHl was isolated from Chrysanthemum via RT-PCR and RACE. The full length cDNA of CmbHLHl was987bp, and the ORF was630bp that encoded a putitive polypeptide of210amino acids residues. Sequence analysis indicated that CmbHLHl contained HLH typical domain. bHLH domain class transcription factor （ADL36593） came from Malus x domestica was the most similar sequence with CmbHLHl, and the identity was62.98%. Phylogenetic tree analysis showed that CmbHLHl and ILR3（NP₂00279.1） from Arabidopsis thaliana were grouped into the same branch.Quantitive real-time PCR （qRT-PCR） showed that CmbHLHl transcript abundance increased obviously in response to iron deficiency after12h and reached the peak around48h. Hormone treatments indicated CmbHLHl expression was reached a high stable level induced by100mg/1ABA, but repressed by0.5mmol/1SA. CmbHLHl expression level was increased slightly within2h and then reduced gradually to a relative level below WT’s within24h under the treatments of abiotic stresses and MeJA.Plant expression vectors for CmbHLHl gene pCAMBIA1301-（+/-）-Cm6HLH1were also constructed in this report, which were introduced into Chrysanthemum cultivar’Jinba’ via an Agrobacterium tumefaciens EHA105-mediated leaf dish transformation method. Two each of independent transgenic lines of CmbHLHl overexpressed or under-repressed were selected for further investigations and contrasted to wild-type’Jinba’. Under iron deficiency, the roots of35S::（+）CmbHLH1-1and35S::（+）CmbHLH1-2lines contained more irons and stronger acidification response than WT, which indicated that transcription factor CmbHLH1regulated the absorption of irons.