Effects Of Light On Anthocyanin Synthesis And Coloration In Chrysanthemum (Chrysanthemum×morifolium Ramat.)

Anthocyanin is one of the most important plant pigments for flower color, and its synthesis is regulated by the developmental state of plant and the external environmental factors. Light is one of the major environmental factors that affect anthocyanin synthesis and flower coloration. In this study, by controlling the light conditions, chrysanthemum flower color variation was induced. The anthocyanin contents and different gene expression patterns were compared in different materials which were exposed to different light conditions. Promoter fragments of light-induced structural genes were analyzed, and the molecular mechanism of light regulating chrysanthemum coloration was analyzed. This study would enrich the molecular mechanism of flower development regulation, and have practical significance for light in regulation of flower color and improving the quality of flower ornamental value by controlling the light conditions. This study achieved the following results.(1) Chrysanthemum inflorescence was divided into eight different developmental stages. The synthesis and chrysanthemum coloration processes and expression pattens of key genes were closely linked to the flower development process.(2) Chrysanthemum inflorescence shading processing caused the significant decrease of anthocyanin content and inhibited the ligulate coloration. Using semi-quantitative RT-PCR method to analyze the expression patterns of structural and regulatory genes, the results showed that the expression of most genes were inhibited, MYB, DFR and ANS were completely suppressed under dark treatment. Leaf shading also inhibited coloration significantly decreased anthocyanin content, with a significant reduction in inflorescence fresh weight and content of reducing sugar in ligulate.(3) Hight light (15000-16000Lux) processing at bud stage increased the anthocyanin contents and the expression of most genes were increased in chrysanthemum ligulate. Inhibition of coloration by shading processing could be reversed by hight light processing in early flower development. But after a certain inflorescence development stage, hight light processing couldn’t reverses coloration inhibition.(4) Using Genome Walking method, two promoter fragments of DFR and a promoter fragment of ANS were cloned. The promoter software analysis showed that the three promoter fragments contain a number of important cis-acting elements involving in light response and light signal transduction pathway, and elements which were the MYB transcription factor binding sites. Transient expression results verified the function of the promoter fragment.According to these results, it could be concluded that:(1) The chrysanthemum ligulate coloration process is closely linked with the process of flower development;(2) For the normal coloratin of chrysanthemum, light is a required environmental factor which plays a key role in the early flower development;(3) Light increase or inhibit expression of anthocyanin biosynthesis genes to control chrysanthemum color;(4) Regulatory gene MYB of anthocyanin biosynthesis may interact with th promoter region of DFR and ANS gene to regulate anthocyanin biosynthesis in chrysanthemum.