| Flowering plays an important role in the life cycle of plants when the plant converts from vegetative growth to reproductive growth stage stage. Flowering regulation affects on plant biomass. During the history of China’s agricultural development, agricultural producers by topping technology control flowering of crops to improve crop yields. In this thesis, Jerusalem artichoke variety (Qinyu No.2) was conducted in soil pot experiments to study the effects of defloration (removing flower) on biomass and distribution profiles of sugar in QY-2. Studies have shown the transcription factor NF-YB are involved in photoperiod pathways to regulate flowering of plants and stress response. In this study, five HtNF-YB genes were cloned from Jerusalem artichoke (Nanyu No.1), and their tissue expression patterns were analyzed both in whole growth period and seedlings under drought, high salt conditions. Subcellular localization of HtNF-YB was examined by transiently expressing a translational fusion with green fluorescent protein (GFP) in onion epidermal cells. The major results were listed as follows:1. Defloration experiments showed that leaves mainly accumulated reducing sugar while tuber and stem mainly reserved non-reducing sugar. Total biomass of QY-2 in the flowering period reached a maximum and later the aboveground biomass started to decrease while underground biomass continued to increase. Production of tubers and content of sugar were significantly affected under defloration on QY-2, especially number and size of tubers, which increased 39.67% and 59.46% respectively. Defloration resulted in higher yield which improved 22.53% compared to the control. Defloration was observed to decrease the total soluble sugar content while play fewer role in reducing sugar in tuber. The content of 1-Kestose was raised 32.47% but other sugar ingredients were not changed.2. Five HtNF-YBs were cloned in the Jerusalem artichoke and sunflower EST database based on known NF-YB sequences that had been identified from other species. Sequence analysis indicates that the five genes possessed typical conserved domains H2A, and had high homology with known NF-YB members of Arabidopsis. HtNF-YB2 owned functional amino acid region VSR, which had been found in AtNF-YB2 and AtNF-YB3, it implied that HtNF-YB2 has the same or similar function with AtNF-YB2 and AtNF-YB3 in flowering.3.To investigate the expression pattern of five HtNF-YB genes in the roots, stems and leaves of whole growth period Jerusalem artichoke and response to PEG6000 induced drought stress and NaCl induced salt stress, RT-PCR experiments were performed. The results of RT-PCR analysis indicated that HtNF-YB2, HtNF-YB11 and HtNF-YB13 were specificly expressed in leaves while HtNF-YB8 in roots and flowers. Defloration had some effect on the expression patterns of HtNF-YB2 and HtNF-YB 10. Five HtNF-YB genes may play important role in response to salt stresses, and four HtNF-YB (HtNF-YB2, HtNF-YBlO, HtNF-YB11 and HtNF-YB13) genes were responsive to drought stesses, respectively.4. To investigate the five HtNF-YB genes function, we fused the entire encoding region of HtNF-YBs into the expression vector pCAMBIA1302, then transformed into Agrobacterium tumefaciens EHA105. The integrated vector was introduced into Arabidopsis thaliana using floral dip transformation method to gain F1 generation. The integrated vector was introduced into onion epidermal cells using a particle bombardment method to detect subcellular localization of HtNF-YB transcription factor proteins. Transformed cells were incubated for 12-24 h at 25℃ in the dark and localization of the fusion proteins was detected using Laser Scanning Microscope. The results of subcellular localization indicated that HtNF-YB2, HtNF-YB8 and HtNF-YB 13 were able to localize into the nucleus. |
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