MicroRNA evolution in the genus Arabidopsis.Comments Comment on: Plant Cell. 2010 Apr;22(4):1090-103; PMID: 20407023, Comment on: Plant Cell. 2010 Apr;22(4):1074-89; PMID: 20407027

摘要

MicroRNAs (miRNAs), a plentiful class of small RNAs in plants, are processed from single-stranded RNA precursors that form imperfect stem-loop foldback structures (reviewed in Voinnet, 2009; see figure). The resulting 20- to 24-nucleotide miRNAs are involved in posttranscriptional downregulation of genes whose transcripts are targeted based on sequence complementarity. MIRNA genes, the loci that encode the RNA precursors, fall into two main categories in plants (reviewed in Axtell and Bowman, 2008; Axtell, 2008). The first includes several MIRNA families that are deeply conserved among plant lineages and are highly expressed. miRNAs from this category participate in processes ranging from development to responding to biotic and abiotic stresses. By contrast, MIRNAs in the much larger, second category are not broadly conserved and, in general, are expressed at much lower levels. What roles, if any, most miRNAs from this category play in plants are not clear (reviewed in Axtell, 2008).