Molecular Cloning And Analysis Of CONSTANS Homologs From Nicotiana Tabacum

The initiation of flowering is a critical trait of the plant transition from the vegetative stage toreproductive stage. Plants possess an extraordinarily well-adapted network of pathways to respond toenvironmental and internal signals. This network controls the flowering transition, played a decisiverole in the environmental adaptation and procreation. The photoperiod pathway inputs light, day length,and the circadian clock to promote the floral transition. CONSTANS (CO) is a key component of thispathway, triggering the production of the mobile florigen hormone FT that induces flowering. The COgene encods an transcription factor with two B-box-type zinc fingers and a CCT domain. Theexpression of CO mRNA is regulated by the daylength and the circadian clock. The level of COtranscription exhibits rhythmic expression patterns in a day. The results are as follows:(1) Genes cloning of CO homologous from Nicotiana tabacumWe designed the primers using the S. tuberosum CO gene sequence and the SOL genomics network.Three genes of CO homologous were isolated from Kutsaga Mammoth10(Nicotiana tabacum cv.Kutsaga Mammoth10) and designated NtCO1, NtCO2and NtCO3.(2) Sequence analysis of CO homologousSequence analysis through bioinformatics showed that the three of predicted proteins contain twoB-box-type zinc fingers and a CCT domain. Analysis based on amino acid sequence alignment andphylogenetic analysis showed that NtCO1, NtCO2and NtCO3protein were belonged to CO family andshowed higher identities with CO homologous from Solanum tuberosum (StCO) and Solanumlycopersicum (SlCO). NtCO1and NtCO2were blonged to subgroup I of the CO family, and NtCO3belonged to the subgroup III.(3) Expression patterns of NtCO1Semi-quantitative RT-PCR analysis showed that NtCO1was expressed specifically and strongly inleaf tissues and in stems but weakly in root tissues. And it was expressed more strongly in thereproductive stage and in the middle stage of vegetative than that in the young stage. Real time PCRanalysis showed that the expression of NtCO1mRNA exhibits rhythmic patterns, and these patterns wereregulated by the daylength.The results of this paper provide meaningful information for further studies of the functions of COfamily in tobacco, the germplasm resources innovation and molecular breeding.