干旱锻炼对B73自交后代当代干旱胁迫记忆基因表达及其启动子区DNA甲基化的影响

Effects of drought hardening on contemporary expression of drought stress memory genes and DNA methylation in promoter of B73 inbred progeny

植物可能会记住已有的逆境刺激,且这种记忆可以跨代遗传。为研究G_(0)代干旱锻炼对玉米B73 G_(1)代当代干旱胁迫记忆基因表达的影响及其启动子区DNA甲基化的影响,实验用20%PEG-6000模拟干旱条件,选取在玉米和拟南芥已知的当代均具有干旱胁迫记忆特性的6个基因为研究对象,利用qRT-PCR技术分析这些基因的表达水平变化,并进一步利用重亚硫酸盐测序PCR技术分析在2个世代中表达差异最显著基因启动子区的DNA甲基化率变化规律。结果表明:干旱胁迫上调了6个当代胁迫记忆基因的表达水平,均呈+/+模式,同当代多次干旱胁迫时表达水平变化趋势一致,且G_(1)代表达水平显著高于G_(0)代;干旱胁迫降低了GRMZM2G_(0)88396基因启动子区的甲基化水平,检测区1两个世代DNA甲基化率的降低主要由CHG和CHH甲基化水平降低造成,检测区2 DNA甲基化率的降低主要是由CG和CHH甲基化水平降低造成,G_(1)代2个检测区总胞嘧啶甲基化率均显著低于G_(0)代,说明G_(0)代干旱锻炼使G_(1)代GRMZM2G_(0)88396基因启动子区的DNA甲基化修饰产生了可遗传的变异,它可能直接参与GRMZM2G_(0)88396基因的表达。

Plants may remember the existing stresses,and this memory can be passed down across generations.To study the effects of drought hardening in G_(0) generation on the contemporary drought stress memory genes’expression and DNA methylation in promoter region in G_(1) generation,20%PEG-6000 was used to simulate drought condition,qRT-PCR was used to analyze the expression level changes of six genes with drought-stressed memory function in maize and Arabidopsis.The changes of DNA methylation rates in the promoter regions of the most differentially expressed gene was analyzed by bisulfite sequencing technology.The results showed that the expression of six genes were up-regulated under drought stress in a+/+mode,and the expression level of G_(1) generation was significantly higher than that of G_(0) generation.Drought stress reduced the DNA methylation’level in the promoter region of GRMZM2G_(0)88396 gene.The reduction of methylation in the detection region 1 of two generations was mainly caused by the reduction of CHG and CHH methylation level,the decrease of methylation in the detection region 2 was mainly caused by the decrease of CG and CHH methylation level.The total cytosine methylation rate of G_(1) generation was significantly lower than that of G_(0) generation,suggesting that drought exercise in G_(0) generation resulted in heritable variation of DNA methylation in the promoter region of GRMZM2G_(0)88396 gene in G_(1) generation,which may be directly involved in the expression of GRMZM2G_(0)88396 gene.