火龙果组培苗DNA甲基化变化及应答赤霉素效应
DNA methylation variation of in vitro pitaya shoots and its response to exogenous GA application

以火龙果优良品种‘紫红龙’组培苗为试材，利用MSAP分子标记，探讨了棱数变异现象与DNA甲基化可能存在的联系，分析了培养时间及继代次数对组培苗DNA甲基化的影响；通过在培养基中添加0（对照）、1.5、3.0、4.5及6.0 mg/L GA，处理5 d后，检测DNA甲基化变化，阐述赤霉素对DNA甲基化变化的影响。结果显示：棱数变异与DNA甲基化水平变化并不存在相关性，而与少数位点的甲基化状态有关；随培养时间的延长和继代次数的增加，组培苗DNA甲基化水平呈现出升高的趋势；随GA质量浓度的增加，外胞嘧啶半甲基化水平呈先升高后降低的趋势，与内源GA含量变化趋势一致，而内胞嘧啶全甲基化水平呈先降低后升高的趋势；外源GA影响了内源GA的积累，与对照相比，DNA甲基化变异率分别提高3.6%、4.5%、 3.1%和2.7%，表明火龙果组培苗DNA甲基化对低浓度GA敏感，而对高浓度GA敏感性降低。
Based on MSAP system,we investigated the potential relationship between genomic DNA methylation variation and arris variation of in vitro pitaya (Hylocereus undatus ‘Zihonglong’) shoots.DNA methylation levels and patterns were detected under different subculture duration and cycles using MSAP marker.Also,the relationship between exogenous GA concentration (0,1.5,3.0,4.5,and 6.0 mg/L),endogenous GA content and DNA methylation variation were illustrated.The results showed that no significant correlation was observed between arris and DNA methylation variation.DNA methylation levels of in vitro shoots increased along with the elongation of culture time and subculture cycles.The ratio of semi-methylation in external cytosine were firstly reduced,followed by an increase,which was somewhat consistent with variation of endogous GA contents (406.7,424.3,440.6,398.6 and 409.1 pg/mL).Ratio of full methylation in internal cytosine of CCGG sites demonstrated a negative correlation with the change of ratio in external cytosine,indicating that,exogenous GA might considerably influence the accumulation of endogenous GA.Furthermore,different forms of methylation patterns might be converted to each other,and thus remained the stability of total DNA methylation level.Along with the increase of the exogenous GA concentrations,the mutation rate of DNA methylation decreased (3.6%→4.5%→3.1%→2.7%),which revealed that,DNA methylation variation of pitaya was more sensitive to low GA concentration.