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Double-stranded RNA binding proteins DRB2 and DRB4 have an antagonistic impact on polymerase IV-dependent siRNA levels in Arabidopsis. | LitMetric

AI Article Synopsis

  • - The study investigates the roles of double-stranded RNA binding proteins DRB2 and DRB4 in the accumulation of PolIV-dependent siRNAs (p4-siRNAs) in plants, which are essential for DNA methylation processes. - Knockout of DRB2 increases p4-siRNA levels in flowers without affecting other types of small RNAs, suggesting its specific role, while DRB4 mutations lead to variable reductions in p4-siRNAs and increased levels of other siRNAs. - The research highlights the antagonistic functions of DRB2 and DRB4, as transgenic plants overexpressing DRB2 display characteristics similar to drb4 mutants, affecting p4-siRNA accumulation both in floral and vegetative tissues.

Article Abstract

Biogenesis of the vast majority of plant siRNAs depends on the activity of the plant-specific RNA polymerase IV (PolIV) enzyme. As part of the RNA-dependent DNA methylation (RdDM) process, PolIV-dependent siRNAs (p4-siRNAs) are loaded onto an ARGONAUTE4-containing complex and guide de novo DNA methyltransferases to target loci. Here we show that the double-stranded RNA binding proteins DRB2 and DRB4 are required for proper accumulation of p4-siRNAs. In flowers, loss of DRB2 results in increased accumulation of p4-siRNAs but not ta-siRNAs, inverted repeat (IR)-derived siRNAs, or miRNA. Loss of DRB2 does not impair uniparental expression of p4-dependent siRNAs in developing endosperm, indicating that p4-siRNA increased accumulation is not the result of the activation of the polIV pathway in the male gametophyte. In contrast to drb2, drb4 mutants exhibit reduced p4-siRNA levels, but the extent of this reduction is variable, according to the nature and size of the p4-siRNAs. Loss of DRB4 also leads to a spectacular increase of p4-independent IR-derived 24-nt siRNAs, suggesting a reallocation of factors from p4-dependent to p4-independent siRNA pathways in drb4. Opposite effects of drb2 and drb4 mutations on the accumulation of p4-siRNAs were also observed in vegetative tissues. Moreover, transgenic plants overexpressing DRB2 mimicked drb4 mutants at the morphological and molecular levels, confirming the antagonistic roles of DRB2 and DRB4.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153974PMC
http://dx.doi.org/10.1261/rna.2680711DOI Listing

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