Effect Of GA On Chinese Cabbage (Brassica Campestris L.ssp Pek Inesis) Flowering Induction And Production Of Late-bolting Transgentic Chinese Cabbage Via RNA-interference Approach

Plant growth and development can be affected by genetic factors, internal and external environments. Different signal transduction pathways and their Cross-talking have been discovered in plant development. In most cases, gibberellin is involved in floral transferring process, and performs diverse function. In this paper, two ecotypes of Chinese cabbage (Brassica Campestris L,ssp pekinesis) B-17 (late-bolting) and 1039 (early-bolting) imbred lines were selected to explore the mechanism of GA and LFY gene in flowering pathway. LFY gene fragment was isolated from the bud of Chinese cabbage by RT-PCR method, and double strand RNA interference expression vector was constructed. The transgenic plants of 1039 imbred line were obtained through Agrobacterium tumefacien transformation, and their morphology, physiology and molecular biology were analyzed. The main results were as follows:(1) Both ecotypes of Chinese cabbage showed earlier flowering with GA treatment, which changed in the substance of metabolism, enzyme activities, DNA methyl level and endogenous GA content. With GA concentration increased, the contents of total soluble sugar, sucrose, starch, soluble protein and endogenous GA increased as well as the activities of POD , a -amlyse activities, but the activities of esterase changed little, DNA methyl level is then reduced. Under the same GA treatment, 1039 line flower earlier than B-17.(2) The relationship between GA concentration and LFY gene expression were analyzed in seed, seedling and bud of Chinese cabbage by Northern blot and relatively quantitative PCR (RQRT-PCR). The result showed that the amount of LFY -mRNA expression was positively correlated with the concentration of GA treatment. GA treatment promoting plants to bloom was probably due to increase expression of LFY gene in different development stage.(3) Through changing pH value and agarose concentration of culture medium, we developed a method for embryo and adventitious bud induction. The MS medium supplemented with 6-BA 5mg.L-1, NAA 0.5mgL-1, pH 6.0-6.2, agrose 0.8-0.9% was found to be optimum for embryo inducing in 1039 imbred line, and the frequency of induction was about 1.0%. While pH 5.7-5.8, agrose 1.0-1.2% was found to be optimum for adventitious...