Journal
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Volume 23, Issue 9, Pages -Publisher
MDPI
DOI: 10.3390/ijms23094977
Keywords
RNA silencing; suppressor; G-U wobble; RNA virus; plant; RNA-protein interaction
Funding
- Deutsche Forschungsgemeinschaft, DFG [CRC648, RTG1591]
- Academic Exchange programs DAAD (German Academic Exchange Service program)
- STMCNR (Italy)
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Plant viruses can produce suppressor proteins that inhibit RNA silencing, a mechanism of antiviral plant immunity. These proteins can bind to virus-derived siRNAs and miRNAs, influencing cellular gene expression. The study found that a specific viral suppressor protein, p19, can bind to different miRNAs with varying affinities due to specific features in the RNA and protein molecules. These findings provide important insights into the efficiency and adaptability of the plant antiviral immune response.
Many plant viruses express suppressor proteins (VSRs) that can inhibit RNA silencing, a central component of antiviral plant immunity. The most common activity of VSRs is the high-affinity binding of virus-derived siRNAs and thus their sequestration from the silencing process. Since siRNAs share large homologies with miRNAs, VSRs like the Tombusvirus p19 may also bind miRNAs and in this way modulate cellular gene expression at the post-transcriptional level. Interestingly, the binding affinity of p19 varies considerably between different miRNAs, and the molecular determinants affecting this property have not yet been adequately characterized. Addressing this, we analyzed the binding of p19 to the miRNAs 162 and 168, which regulate the expression of the important RNA silencing constituents Dicer-like 1 (DCL1) and Argonaute 1 (AGO1), respectively. p19 binds miRNA162 with similar high affinity as siRNA, whereas the affinity for miRNA168 is significantly lower. We show that specific molecular features, such as mismatches and 'G-U wobbles' on the RNA side and defined amino acid residues on the VSR side, mediate this property. Our observations highlight the remarkable adaptation of VSR binding affinities to achieve differential effects on host miRNA activities. Moreover, they show that even minimal changes, i.e., a single base pair in a miRNA duplex, can have significant effects on the efficiency of the plant antiviral immune response.
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