Study On Genetic Regulation Of Flowering Time In Chrysanthemum Induced By AtLEAFY

Chrysanthemum (Dendranthema morifolium), one of the ten traditional famous flowers in China, is Asteraceae perennial herb plant. Moreover, it is regarded as the city flower in lots of cities, such as Taiyuan, Kaifeng, and Wuhu. According to time of flowering, chrysanthemum was divided into early and late flowering chrysanthemum. The flowering time of early chrysanthemums which is always in June or July is usually used for decorating street, because of the defects of single species, small flowers and low quality of ornamentation. However, the major precious chrysanthemums cultivars are short-day plant, later flowering in fall. Owing to seasonal restrictions, the commercial value of these cultivars is decreased tremendously. Although routine regulating methods of flowering time have been made a lot of research, such as gardening cultivation techniques, regulating exposure time and temperature, the process of these methods is complicate and cost a lot.With Agrobacterium-mediated leaf disc transformation method, chrysanthemum cultivar Huang Jinhu (Dendranthema morifolium (the Ramat) Kitamurd) and Y4transgenic chrysanthemum (transformation with rd29Ar.SOCl vector for Huang Jinhu) were introduced into flowering time function gene LEAFY which expression controlled by rd29A promoter. And a new chrysanthemum germplasm which can control flowering time with simple and easy method was obtained. The main results were as follows:1. Construction of plant expression vector:the floral meristem characteristics gene LEAFY was extracted and amplified from Arabidopsis mRNA. Then through digestion, ligation and other methods, LEAFY gene was inserted into the downstream of the rd29A promoter within the plant expression vector reformed pCambia2300(contains stress inducible promoter rd29A). The new vector was transferred into soil Agrobacterium tumefaciens strain LBA4404.2. Transformants obtainment:through leaf disc transformation chrysanthemum varieties Huang Jinhu and Y4strains respectively,54and49resistant shoots were obtained and using resistance roots screening media for the same number of regeneration seedings which cultured in non-selection pressure culture media,23and45root resistant seedlings were selected. And3and4positive seedlings were checked out through PCR to detect root resistant seedlings, which were named L1, L2and L3(wild type genetic background), as well as SL1, SL2, SL3and SL4(Y4genetic background). Conversion rate were2.02%and3.73%.3.NaCl-stress induced experiment:four different concentrations (50,100,150and200mmol/L) NaCl solution were selected to stress induce L1and SL2transgenic lines. The experimental results show that:under the solution treatment of150mmol/L and100mmol/L NaCl, LEAFY gene expression reached the highest levels in L1and SL2respectively. And because these two concentrations for normal growth of chrysanthemum had no significant effect, the conclusion was drawed that the two concentrations is the best stress-induced concentration.