Transgenically expressed viral RNA silencing suppressors interfere with microRNA methylation in Arabidopsis.
HEN1-dependent methylation of the 3'-terminal nucleotide is a crucial step in plant microRNA (miRNA) biogenesis. Here we report that several viral RNA silencing suppressors (P1/HC-Pro, p21 and p19) inhibit miRNA methylation. These suppressors have distinct effects on different miRNAs. We also show that miRNA* is methylated in vivo in a suppressor-sensitive manner, suggesting that the viral proteins interfere with miRNA/miRNA* duplexes. p19 and p21 bind both methylated and unmethylated miRNA/miRNA* duplexes in vivo. These findings suggest miRNA/miRNA* as the in vivo substrates for the HEN1 miRNA methyltransferase and raise intriguing possibilities regarding the cellular location of miRNA methylation.
Yu
Bin
B
Department of Botany and Plant Sciences and Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
Chapman
Elisabeth J
EJ
Yang
Zhiyong
Z
Carrington
James C
JC
Chen
Xuemei
X