An Analysis Of DNA Methylation & Related Gene Expression In Chrysanthemum Flowering Process By Short Daylight Treatment

This study respectively on Chrysanthemum cultivar "he hua xian zi", "qiu shui chang liu" and "nan nong hong xiu" of short day treatment, observation records of plant height and flowering time. To understand the DNA methylation features of Chrysanthemum during its flowering process, we employed the techniques of methylation sensitive amplification polymorphism(MSAP) and high performance liquid chromatography(HPLC) to detect the DNA methylation level of Chrysanthemum, in the process of flowering. The techniques of real-time fluorescence quantitative PCR were conducted to detect the expression of flowering gene FT and related genes of DNA methylation and demethylation of the Chrysanthemum cultivar "nan nong hong xiu". The results were as follows:(1) Effect of short days on plant height: After 43 days of short day treatment, the Plant height of treatment group was significantly lower than the control. While for late flowering varieties after short day treatment on 28 d, compared with control group, there was no significant difference. That showed that it is more sensitive for early flowering varieties to short-day treatment, and their reproductive growth demanded relatively a short day induced time.(2) Effect of SD on flowering: The time to capituium bud appearance and early blooming from the date of planting were significantly shorter than those of the control for both early and late-flowering cultivar. Capituium development of the early- flowering cultivar significantly accelerated compared with that of the control, which was different with the late-flowering cultivar.(3) DNA methylation changes during flowering under SD treatment: DNA methylation percentage changed dynamically during flower development. For the early-flowering cultivar, DNA methylation was 42.2%-51.3% before capituium bud appearance and 30.5%-44.5% after capituium bud appearance. The respective DNA methylation percentages for the late-flowering cultivar were 43.5%-56.0% and 37.2%-44.9%.(4) DNA methylation changes at early flowering stage following SD treatment: Percentage of DNA methylation of Chrysanthemum decreased significantly during floral development. The decline in DNA methylation was elevated in the early-flowering cultivar compared with that of the late-flowering cultivar.(5) The expression of CmFT in chrysanthemum flowering under short day treatment: The expression of CmFT was significantly increased from squaring, and the treatment group in the period of budding and flowering period was higher than the control.(6) The expression of genes related to DNA methylation and demethylation in chrysanthemum flowering under short day treatment: The expression of CmMET1 and CmCMT3 were decreased in the process of the short-day treatment on Chrysanthemum flowers, and the short day treatment group decreased greater. The expression of CmDRM2 rose in the process of the short-day treatment on Chrysanthemum flowers, the vegetative period and floral bud emergence period of the control group has little change during the first three period. The expression of CmDME has little change in first three periods, and increased in the flowering period.