非编码核酸TAS1干扰植物抗热基因的分子机制

在模式植物拟南芥中，非编码核酸TAS1沉默抗热基因HTT1。但是，来源于TAS1的ta-siRNAs在热激条件下却没有这种沉默作用。我们推测，热激改变了ta-siRNA对靶基因的干扰作用。本课题将分析TAS1和ta-RNA干扰抗热基因的遗传机制。我们将选择小RNA生成有缺陷的突变体，通过TAS1的过量表达，了解TAS1和ta-siRNA在热激条件下对抗热基因表达和植株抗热性的影响；利用依赖RNA的甲基化突变体，考察内源TAS1或ta-siRNA对抗热基因甲基化的影响；在体内外测定TAS1或小RNA与靶基因mRNA在高温下形成双链RNA的效率，了解高温和极端高温影响TAS1或小RNA活性的原理；对TAS1基因进行缺失和定点突变，发现那些在TAS1和ta-siRNAs序列上对抗热基因表达起关键作用的区域或核苷酸，明确TAS1干扰抗热基因的机制，为发展RNA干扰和植物抗热性的理论提供科学依据。

In the model plant Arabidopsis, non-coding nucleotide TAS1 silence thermotolerance gene HTT1. However, the ta-siRNAs derived from TAS1 do not show such silenceing under heat shock. We suppose that heat shock changes RNA interference of ta-siRNAs to the target genes. This proposed project will analyze genetic mechanism underlying RNA interference of thermotolerance genes. We will choose the mutants deficient in ta-siRNA biogenesis, overexpress TAS1 or ta-siRNA and examine the effects of heat shock on expression of thermotolerance gene and thermotolerance of plants.some mutants deficient in RNA-dependent methylation will be used to investigate the effects of TAS1 or ta-siRNA on methylation of thermotolerance gene. To understand the effects of high and extremely high temperature on the activities thermotolerance gene, in vivo and in vitro detection of the efficiency for double-stranded RNA production will be performed. We will mutagenize the TAS1 gene for the selection of the domains and key nucleotides that play important role in thermotolerance. We will explore the molecular mechanism underlying RNA interferance to thermotolerance, and thus advance the theory of RNA interferance and plant thermotolerance.