The Molecular Mechanism Of Leaf Color Transition In The Bolting Process Of Chinese Cabbage

Premature bolting of Chinese cabbage (Brassica rapa L. ssp. pekinensis) is a phenomenon that bolting at a improper time before its vegetative plants ripen, then the vegetable will lose value,It causes a great loss in production. It has great significance to study the Physiological and Molecular mechanism connected with bolting of Brassica.rapa,especially the genes associated with bolting and flowering in vernalization pathway.Chinese cabbage will bolting and flowering after vernalization , the leaf color changes before the bolting, stems elongate and the plant start to bud and bolt after the leaf color changes from bright green to dark grey without being shiny or lustrous .the changes of the leaf color seems to be a physiological signal of the bolting for Chinese cabbage ,the phenomenon is particularly acute for the weak winterness cultivars, so we speculate that the changes of leaf color is relevant with the bolting and flowering process. the genes and protein expression varies before and after leaf color changes. In present study, we used four cultivars of Chinese cabbage that were different in winter to study the molecular mechanism of reproductive development by testing the related genes and proteins expression. We took samples of fresh young leaves in six development stages for hormone levels Determination and 2-D electrophoresis,which are before and after vernalization, floral bud differentiation period,stem differentiation period,the period of leaf color transition and the stem elongation period. Then we took samples at root,dwarf stem, fresh leaves at growing point, proximal leaves, distal leaves in the period of leaf color transition for FT and LFY RT-PCR all together with the samples mentioned above. Main results were as follows:1. It turns out that the hormone content is associated with the leaf color changes in the bolting process, different winterness varieties get content peaks of IAA and GA3 in the period of leaf color transition respectively in bolting process. The stems begin to elongate after this stage.The changes of leaf color is a physiological signal in cabbage bolting.2 . FT gene expresses stronger in weak winterness cultivars than in strong winterness cultivars; It doesn't express or express very weak in the whole vegetative growth stage, it expresses stronger and stronger after the bud differentiation stage, and expresses very strongly in the leaf color transition period and stems elongation period .FT gene doesn't express in roots and dwarf stems, it expresses in the fresh leaves at growing point, proximal leaves and distal leaves. FT expresses strongly in proximal leaves and very weak in distal leaves in weak winterness cultivars, however, in strong winterness cultivars,FT expresses both strongly in proximal leaves and distal leaves .3. LFY gene doesn't express before vernalization,expresses strongly in the bud differentiation period,the leaf color transition period and stems elongation period,most strongly in the fresh leaves at growing point.it expresses strongly in proximal leaves and distal leaves,it doesn't express in roots ,and express very weak in dwarf stems.4. We found 18 new proteins espresses after leaf color changes,and 17 proteins don't espresses anymore after this transition, There are also 21 proteins are up-regulation of experssion and 29 are down-regulation of experssion according to analysis and comparation.5. 17 protein spots were identified using MS.and 16 of them are successfully identified. 1 of them is related with transcriptional regulation, 2 of them are related with signal or energy transmission,6 proteins participate in cell growth and metabolism,and the last one is structural protein.