Endogenous TasiRNAs mediate non-cell autonomous effects on gene regulation in Arabidopsis thaliana.
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.


RESULTS
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
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.
Schwab
Rebecca
R
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America.
Maizel
Alexis
A
Ruiz-Ferrer
Virginia
V
Garcia
Damien
D
Bayer
Martin
M
Crespi
Martin
M
Voinnet
Olivier
O
Martienssen
Robert A
RA
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D035683:MicroRNAs / Q000378:metabolism*; D018613:Microscopy, Confocal; D008957:Models, Genetic; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D034741:RNA, Small Interfering / Q000378:metabolism*; D015533:Transcriptional Activation
D029681:Arabidopsis Proteins; D035683:MicroRNAs; D034741:RNA, Small Interfering