rDNA copy number of WT and RNA silencing mutant strains. Quantitative PCR analysis on genomic DNA extracted from WT, silenced (6xw) and quelling defective (qde-1, qde-2, qde-3) strains. To evaluate the rDNA copy number we compared the Ct value from the rDNA locus relative to the Ct value from the actin locus. A. rDNA copy number was evaluated in different clones from each quelling defective strains and compared relative to WT and the silenced 6xw strains. The error bars represent the standard deviation of triplicates in the qPCR reaction. B. Mean of the rDNA copy number value obtained from the different clones of quelling defective strains showed in A compared to WT and 6xw strains. The error bars denote the standard deviation. Asterisk indicate significant differences using two-tailed Student's t-test of all data points, *P < 0.001.