Abstract
Cell type-specific expression of microRNAs (miRNAs) plays important roles in development of multicellular organisms. It is reported that the spatial restriction of miRNA, miR165 and/or miR166 (miR165/166) of Arabidopsis thaliana, plays a critical role in the polarity-dependent leaf development along the adaxial (central)-abaxial (peripheral) axis. miRNAs are transcribed as long precursors and progressively processed by the factors including Dicer-family protein. However, the cell type-specific regulatory mechanism of miRNA is poorly understood. Here, we show several lines of evidence that ASYMMETRIC LEAVES2 (AS2), ASYMMETRIC LEAVES1 HDT1/HD2A and HDT2/HD2B control the distribution of miR165/166 in Arabidopsis. The combination of the as2 mutation and the inhibition of histone deacetylase(s) led plants to form abaxialized leaves through the altered distribution pattern of miR165/166. Ectopic and/or over-production of AS2 reduced the accumulation level of miR165/166. This negative regulation of the accumulation of miR165/166 by AS2 required endogenous AS1.
