Endogenous TasiRNAs mediate non-cell autonomous effects on gene regulation in Arabidopsis thaliana
6 páginas, 3 figuras ; Background Different classes of small RNAs (sRNAs) refine the expression of numerous genes in higher eukaryotes by directing protein partners to complementary nucleic acids, where they mediate gene silencing. Plants encode a unique class of sRNAs, called trans-acting small interfering RNAs (tasiRNAs), which post-transcriptionally regulate protein-coding transcripts, as do microRNAs (miRNAs), and both sRNA classes control development through their targets. TasiRNA biogenesis requires multiple components of the siRNA pathway and also miRNAs. But while 21mer siRNAs originating from transgenes can mediate silencing across several cell layers, miRNA action seems spatially restricted to the producing or closely surrounding cells. Principal Findings We have previously described the isolation of a genetrap reporter line for TAS3a, the major locus producing AUXIN RESPONS FACTOR (ARF)-regulating tasiRNAs in the Arabidopsis shoot. Its activity is limited to the adaxial (upper) side of leaf primordia, thus spatially isolated from ARF-activities, which are located in the abaxial (lower) side. We show here by in situ hybridization and reporter fusions that the silencing activities of ARF-regulating tasiRNAs are indeed manifested non-cell autonomously to spatially control ARF activities. Conclusions/Significance Endogenous tasiRNAs are thus mediators of a mobile developmental signal and might provide effective gene silencing at a distance beyond the reach of most miRNAs ; This work was supported by grants from the National Science Foundation (DBI-0421604) and the Robertson Research Fund to R.M.; a starting grant from the European Research Council (ERC, Frontiers of RNAi, 210890) to O.V.; an ANR grant (ANR06 GPLA 011) to A.M. and M.C.; a grant from the European Union integrated project SIROCCO (Silencing RNAs: Organisers and Coordinators of Complexity in Eukaryotic Organisms; LSHG-CT-2006-037900) to D.G; an EMBO long-term fellowship (ALTF 864-2005) and a postdoctoral fellowship from DuPont to R.S.; a European Union Marie Curie fellowship (041419) to V.R.F.; and a research fellowship from the DFG to M.B. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript ; Peer reviewed