两个水稻品种镉积累相关基因表达及其分子调控机制

Comparison of Cadmium-Accumulation-Associated Genes Expression and Molecular Regulation Mechanism between Two Rice Cultivars(Oryza sativa L.subspecies japonica)

内源小干扰RNAs(small interfering RNAs,siRNAs)和DNA甲基化在植物生长发育和适应环境胁迫中调控基因的表达。对于植物来说,镉(Cadmium,Cd)是一种非必需且具有毒性的元素。为研究DNA甲基化和siRNAs在水稻(Oryza sativa L.)Cd积累相关基因表达调控方面的作用,比较了Cd高积累品种(秀水110)和Cd低积累品种(秀水11)中Cd积累相关基因的表达情况。结果表明,在秀水110和秀水11叶片中,除植物Cd抗性蛋白(plant cadmium resistance protein,PCR)基因家族成员OsPCR1的表达水平呈现出显著的差异外,其他Cd积累相关基因的表达水平不存在显著的差异。说明OsPCR1基因可能参与调控水稻体内Cd的积累。利用荧光实时定量PCR(qRT-PCR)技术研究了水稻叶片中siRNA表达水平在水稻5个不同生长发育期中的变化情况。数据显示水稻叶片中与OsPCR1基因外显子2匹配的siRNA的丰度和OsPCR1基因的表达水平呈负相关。进一步利用McrBC-qRT-PCR技术研究OsPCR1基因外显子2甲基化水平在水稻5个不同生长发育期中的变化情况表明,在Cd处理条件下水稻叶片中OsPCR1基因外显子2甲基化水平和该基因的表达水平也呈负相关。说明,在水稻体内Cd积累的过程中,该siRNA和OsPCR1基因外显子2甲基化可能参与调控OsPCR1基因的表达。这些结果对于研究OsPCR1基因的功能和培育Cd低积累水稻品种具有重要的理论指导意义。

In plants, as in other eukaryotes, endogenous small interfering RNAs （siRNAs）, a class of small non-coding RNAs, and DNA methylation regulate gene expression in developmental processes and adaptating to environmental stresses, including Cd stress. Cadmium （Cd） is a non-essential heavy metal and highly toxic to plants. To investigate the regulatory role of siRNAs and DNA methylation on genes involved in heavy metals transport, we compared these genes＇ expression profiles between a high Cd-accumulating rice （Oryza sativa L. subspecies japonica） cultivar （Xiushui 11） and a low Cd-accumulating rice cultivar （Xiushui 110）. At five rice development stages investigated, the difference of these genes expression level between the two rice cultivars was not significant except OsPCR1, indicating OsPCR1 may be important in Cd transport in rice. Furthermore, quantitative real time PCR （qRT-PCR） was performed to examine the expression level of a siRNA matched OsPCR1 second exon. Results indicated that the expression level of the siRNA negatively correlated with OsPCR1 expression level at the five stages. In addition, McrBC-qRT-PCR technology was used to determine DNA methylation level, showing that OsPCR1 expression level also nega- tively correlated with OsPCR1 second exon methylation level. These results of regulatory roles of siRNA and DNA methylation on OsPCR1 expression will contribute to the studies on OsPCR1 fimction and rice breeding for low Cd accumulation.