Biogenesis and Biological Activity of Secondary siRNAs in Plants
Cascades involving TAS1 and TAS2 processing in Arabidopsis. The results rely on the use of CaMV infected plants of which the suppressor TAV interferes with the DCL4/DRB4 activity. The dsRNA intermediates generated by RDR6 accumulating in CaMV infected plants were analyzed. For TAS1c, three main dsRNAs accumulated. The largest and minor one corresponds to a single cut of TAS1c RNA by the AGO1::mir173 RISC, the second one from a double hit by AGO1::miR173 and AGO1::, and the third one by AGO1::miR173 and AGO1(2)::. and are siRNAs at positions 6 and 10 derived from the antisense strand of the dsRNA intermediate. exists as a 21nt 5′A form likely bound to AGO2 and a 22nt 5′U form bound to AGO1. Notably, RISCs can also target TAS1a, TAS1b, and TAS2 RNAs. On the right, a gel ss showed separating single and double-stranded ta-siRNA precursors (S sense RNAs, AS, antisense RNAs).