The Function Of NFT1 In Narcissus Tazetta Var. Chinensis About Flowering And Dormancy

Narcissus tazetta var. chinensis is perennial herbaceous plants, belongs to amaryllidaceae daffodil. In its life cycle there is summer dormancy stage lasting for more than 4 months. From May to the end of July is endodormancy period, and from the end of July to the early September is ecodormancy. Flower transition is induced in three-year old of the bulb at the end of the endodormancy period. So it is critical to know the molecular mechanisms of the dormancy and flowering for the growth regulation of Chinese narcissus.The FT gene has been widely accepted for the regulation of flowering time, and this factor is also considered as the important element that controls winter dormancy. A FT homologous gene, NFT1, has been cloned from Chinese in our lab. The function of NFT1 gene in the regulation of flowering and dormancy in narcissus was mainly studied here.We got the following main results:1. Ectopic expression of NFT1 promotes blossom in Arabidopsis thaliana. Through ectopic expression of NFT1 in Arabidopsis thaliana, we studied the function of NFT1.35S::NFT1 was transfered into wild-type Col and ft deletion mutant ft-3 (Ler background), making NFT1 gene overexcessing in arabidopsis thaliana. the transformants of wild-type Col blossomed ahead of time about 7-10 days and had 5 to 7 leaves fewer than those of Col controls; Although the lines of the 35S::NFT1 construct in ft-3 flowered later than the wild type Ler plants, these lines flowered about 2-3 weeks earlier and made 3 to 10 leaves fewer than the ft-3 controls. We analyzed the transcription level of NFT1 and target of the FT gene, SOC1 in transformants through RT-PCR and qRT-PCR. The expression of NFT1 and SOC1in transformants was strongly higher, than those in their parents, which is consistent with the flowering in advance.2. The expression of NFT1 in Chinese narcissus is closely related to flower transition. We analyzed the the relationship between the expression of NFT1 and flower transition under natural conditions through the qRT-PCR methods.We found that the peak value of the expression of NFTI occurred at the end of July or early of August, that is at the moment of flower transition in three-year-old bulbs.3. High temperature and exogenous ethylene can promote flower transition in chinese narcissus via the upregulation of NFT1. High storage temperature improved the bolting rate and the expression of NFTI in two or three-year old of bulbs. The bolting rate of bulbs was increased when exogenous ethylene was applied at early August during storage and the expression of NFT1 in apices of the bulbs was also improved remarkable within a week or two after the ethylene application.These data indicated that the expression of NFT1 is close to the flowering in Chinese narcissus. Low storage temperature such as 15℃ improved the expression of NFT1, whereas such condition decreased bolting rate extremely. This suggests that other regulation factors might be needed to coordinate with NFT1 to regulate flowering in Chinese narcissus.4. The expression of NFT1 in Chinese narcissus is closely related to dormancy. The relationship between the expression of NFT1 and dormancy, flower transition was analyzed under natural conditions through qRT-PCR methods. Results for two consecutive years showed that the expression of NFT1 in apices falled when the bulbs entered dormancy, but increased gradually and reached its peak at the moment of endormancy release and flower transition.These showed that the improvement expression of NFT1 is closely related to the release of endodormancy and flower transition.The expression of NFTI in leaves rised with the increase of temperature in vegetative growth period. The relative expression of NFTI in leaves and apices were higher in vegetative growth period, then falled when bulbs entered dormancy, and it was extremely low during endodormancy.To sum up, ectopic expression NFTI promote bloom in Arabidopsis. The peak value of NFT1 expression is consistent with the time of flower transition and release of endodormancy in Chinese narcissus. High temperature promoted flower transition and exogenous ethylene improved flowering rate and release of dormancy. Both high temperature and ethylene increased the expression of NFT1 in bulbs. These results suggest that NFT1 was involved in the regulation of flower and dormancy in chinese narcissus. To further study NFT1 with other related genes in regulation flowering and dormancy is helpful to clarify the developmental mechanism of Chinese narcissus.