The Roles of Arabidopsis CDF2 in Transcriptional and Posttranscriptional Regulation of Primary MicroRNAs. Arabidopsis thaliana

The precise regulation of microRNA (miRNA) transcription and processing is important for eukaryotic development. Plant miRNAs are first transcribed as stem-loop primary miRNAs (pri-miRNAs) by RNA polymerase II，then cleaved in the nucleus into mature miRNAs by Dicer-like 1 (DCL1). We identified a cycling DOF transcription factor, CDF2, which interacts with DCL1 and regulates the accumulation of a population of miRNAs. CDF2 binds directly to the promoters of some miRNAs and works as a transcription activator or repressor for these miRNA genes. CDF2 binds preferentially to the pri-miRNAs regulated by itself and suppresses DCL1-mediated pri-miRNA processing. Genetically, CDF2 works in the same pathway as miR156 or miR172 to control flowering. We conclude that CDF2 regulates a group of pri-miRNAs at both the transcriptional and posttranscriptional levels to maintain proper levels of their mature miRNAs to control plant development. Overall design: Examination of small RNA populations in Arabidopsis Wild Type and cdf2 mutant or Wild Type and dcl1-9 mutant

微小RNA（miRNA）的转录与加工精准调控，对真核生物的生长发育至关重要。植物miRNA首先由RNA聚合酶II转录为带有茎环结构的初级miRNA（pri-miRNA），随后在细胞核内被类Dicer 1（DCL1）切割为成熟miRNA。本研究鉴定得到一种循环DOF转录因子CDF2，其可与DCL1相互作用，并调控一类miRNA的积累水平。CDF2可直接结合部分miRNA的启动子区域，作为这些miRNA基因的转录激活因子或阻遏因子发挥功能。CDF2优先结合自身调控的pri-miRNA，并抑制DCL1介导的pri-miRNA加工过程。遗传学实验表明，CDF2与miR156或miR172处于同一通路，共同调控植物开花过程。综上，CDF2可在转录及转录后两个层面调控一类pri-miRNA的表达，以维持其成熟miRNA的适宜水平，进而控制植物生长发育。实验设计：对拟南芥野生型与cdf2突变体，以及拟南芥野生型与dcl1-9突变体的小RNA群体进行检测分析。