破坏光敏色素A改变生长素反应因子8的表达谱

拟南芥生长素反应因子8（auxin response factor8，ARF8）受光诱导表达，涉及光信号转导。为阐明光信号通过光受体传递给ARF8的过程和机理，首先利用半定量RT-PCR分析发现，PhyA的突变促进幼苗中ARF8的表达，而PhyB、Cry1和Cry2的突变对ARF8的表达没有明显影响。进而，利用GUS染色以及半定量和定量RT-PCR方法，系统分析PhyA基因的突变对ARF8基因表达的影响。结果表明，在黑暗、白光和远红光条件下，PhyA突变均明显提高拟南芥（Arabidopsis thaliana）幼苗子叶和叶片中ARF8的表达水平，并且明显降低其在幼苗下胚轴、茎尖和根尖中的表达水平。上述结果说明，PhyA基因的突变组成型地改变了ARF8基因的表达谱。然而，ARF8的突变并未明显改变PhyA的表达。说明在远红光信号通路中，ARF8位于PhyA的下游。

Disruption of Phytochrome A Changes Expression Pattern of Auxin Response Factor 8

The expression of Arabidopsis auxin response factor 8 （ARF8） can be promoted by light and is involved in light signaling. However, little is known about the pathway and mechanism underlying signal transduction from photoreceptors to ARF8.Semi-quantitative RT-PCR analysis revealed that mutation of PhyA elevated the expression of ARF8, but that of PhyB, Cry1 or Cry2 did not change the expression of ARF8 markedly. GUS staining, semi-quantitative RT-PCR and real-time RT-PCR were used to analyze how PhyA systemically affected the expression of ARF8. GUS staining in related GUS lines suggested that mutation of PhyA affects the mRNA expression of ARF8 in an organ-specific manner. In cotyledons, PARFs：GUS showed weak staining but phyA-209 PARF8：GUS showed strong staining. In the shoot apical meristem, hypocotyl and root tip, phyA-209 PARF8：GUS showed weaker staining than did PARF8：GUS. The same expression patterns of ARF8 resulting from disruption of PhyA were observed in dark, white light and far-red light conditions. This expression pattern was further confirmed by semi-quantitative and real-time RT- PCR analysis. However, the expression of PhyA in arf8-1 was almost the same as in the wild type, which suggests that disruption of ARF8 does not change the expression of PhyA. Our results suggest that ARF8 acts downstream of PhyA in far-red light signaling.