Discovery
The presence of ta-siRNAs was originally detected in 2004 by two different lab groups researching the flowering plant arabidopsis. Both papers were published in October within days of each other. One lab group (Peragine et al.) was investigating the Argonaute protein ZIPPY (ZIP), and the other (Vazquez et al.) was trying to identify a specific small interfering RNA (siRNA) pathway. Despite starting at different points, both research groups found their projects involving the plant specific protein, suppressor of gene silencing 3 (SGS3), and the enzyme RNA-dependant RNA polymerase 6 (RDR6). Both groups found that SGS3 and RDR6 are important in the generation of a specific group of small RNAs (sRNAs) termed ta-siRNAs.
Because of key differences that set them apart from other sRNAs, Ta-siRNAs were a new discovery despite sharing similarities with both siRNAs and microRNAs (miRNAs). Unlike miRNAs, it was found that ta-siRNAs are derived from long double-stranded RNA (dsRNA), and their generation is RDR6 dependant. Ta-siRNAs differ from siRNAs because they direct cleavage of transcripts which are not identical. In this way ta-siRNAs are more functionally similar to miRNAs, but are produced in the same manner as siRNAs.
Read more about this topic: Trans-acting Si RNA
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