TasiRNA
TasiRNA, short for trans-acting small interfering RNA, is a class of plant small interfering RNAs derived from transcripts of noncoding TAS genes. TasiRNA production is initiated by a microRNA (miRNA) trigger that binds to a TAS transcript, with TAS3 being the best characterized example in Arabidopsis. In TAS3, miR390 guides an AGO protein to two miR390 target sites; cleavage occurs at one site by the AGO-miRNA complex, while the other site remains non-cleaved. The resulting fragment is converted into double-stranded RNA by RNA-dependent RNA polymerase 6 (RDR6) in a SGS3-dependent manner. Dicer-like enzymes, primarily DCL4, process the dsRNA into 21-nt tasiRNAs in a defined phasing relative to the initial miRNA-guided cleavage site.
The mature tasiRNAs are incorporated into Argonaute-containing silencing complexes and act in trans to regulate other
TAS gene families also include TAS1, TAS2, and TAS4, which generate additional tasiRNAs with distinct targets
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