Disease relevance of RDR6

• Geminivirus VIGS of endogenous genes requires SGS2/SDE1 and SGS3 and defines a new branch in the genetic pathway for silencing in plants [1].

High impact information on RDR6

• When both transcripts are present, a 24-nt siRNA is formed by a biogenesis pathway dependent on DCL2, RDR6, SGS3, and NRPD1A [2].
• These data support a model in which miRNA-guided formation of a 5' or 3' terminus within pre-ta-siRNA transcripts, followed by RDR6-dependent formation of dsRNA and Dicer-like processing, yields phased ta-siRNAs that negatively regulate other genes [3].
• Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance [4].
• The sde1 mutation was specific for posttranscriptional gene silencing induced by transgenes rather than by viruses [5].
• One of these, SDE1, is a plant homolog of QDE-1 in Neurospora crassa that encodes an RNA-dependent RNA polymerase [5].

Biological context of RDR6

• It is known that RDR6 is one of the key components in plant post-transcriptional gene silencing (PTGS), and is likely to function with other silencing components in a genetic pathway in regulating leaf patterning [6].
• Additionally, we show that CaMV infection impairs processing of endogenous RDR6-derived double-stranded RNA, while ORMV prevents HEN1-mediated methylation of small RNA duplexes, suggesting two novel viral strategies of silencing suppression [7].
• While the four DCLs are partially redundant for CaLCuV-induced mRNA degradation, DCL4 in conjunction with RDR6 and HEN1 specifically facilitates extensive virus-induced silencing in new growth [7].
• Work in sde1 background revealed a near-perfect spatial overlap between the patterns of miR171 transcription and activity, supporting the idea that plant miRNAs enable cell differentiation [8].
• These mutations defined two genetic loci, called sgs1 and sgs2 (for suppressor of gene silencing) [9].

Associations of RDR6 with chemical compounds

• RNA silencing of ribulose-1,5-bisphosphate carboxylase/oxygenase and phytoene desaturase was not associated with the spreading of RNA targeting or DNA methylation, indicating that these endogenous RNAs are not templates for SDE1/SGS2 [10].

Other interactions of RDR6

• The RDR6-SGS3-AGO7 pathway was previously identified as regulating the plant vegetative phase change [6].
• We show that plants carrying rdr6, suppressor of gene silencing3 (sgs3) or zippy (zip, also called ago7) in combination with as1 or as2 demonstrate severe morphological defects, and the double mutant plants are generally similar to one another [6].
• In addition, the RNA-DEPENDENT RNA POLYMERASE6 (RDR6) gene acts synergistically with AS1 and AS2 to specify the adaxial polarity and repress the KNOX genes in leaves [6].
• The small RNA populations in other Arabidopsis small RNA biogenesis mutants were also examined; a dcl2/3/4 triple mutant showed a similar pattern to rdr2, whereas dcl1-7 and rdr6 showed reductions in miRNAs and ta-siRNAs consistent with their activities in the biogenesis of these types of small RNAs [11].
• We show that DCL4 is the primary processor of endogenous RDR6-dependent trans-acting siRNAs (tasiRNAs) [12].
• These data suggest that AGO1 functions differentially with 21- and 22-nt miRNAs to engage the RDR6-associated amplification apparatus [13].

Analytical, diagnostic and therapeutic context of RDR6

• Newly generated inoculum from R. sativa was used for biolistic transfer to Arabidopsis thaliana wild-type and silencing-deficient mutants bearing one of sde1, sde2, and sde3 locuses [14].

References