Rep and V2 Suppress Post-Transcriptional Gene Silencing via Distinct Modes of Action.

(BCTIV) is a yield-limiting geminivirus belonging to the genus. The genome organization of BCTIV is unique such that the complementary strand of BCTIV resembles , whereas the virion strand organization is similar to the genus. Geminiviruses are known to avoid the plant defense system by suppressing the RNA interference mechanisms both at the transcriptional gene silencing (TGS) and post-transcriptional gene silencing (PTGS) levels.

High-Pressure-Sprayed Double Stranded RNA Does Not Induce RNA Interference of a Reporter Gene.

In plants, RNA interference (RNAi) is an effective defense mechanism against pathogens and pests. RNAi mainly involves the micro RNA and the small interfering RNA (siRNA) pathways. The latter pathway is generally based on the processing of long double stranded RNAs (dsRNA) into siRNAs by DICER-LIKE endonucleases (DCLs).

Transient expression of intron-containing transgenes generates non-spliced aberrant pre-mRNAs that are processed into siRNAs.

In this study, we show that aberrant pre-mRNAs from non-spliced and non-polyadenylated intron-containing transgenes are channelled to the RNA silencing pathway. In plants, improperly processed transcripts are called aberrant RNAs (ab-RNAs) and are eliminated by either RNA silencing or RNA decay mechanisms. Ab-RNAs transcribed from intronless genes are copied by RNA-directed RNA polymerases (RDRs) into double-stranded RNAs which are subsequently cleaved by DICER-LIKE endonucleases into small RNAs (sRNAs).

Delivery of Hairpin RNAs and Small RNAs Into Woody and Herbaceous Plants by Trunk Injection and Petiole Absorption.

Since its discovery, RNA interference has been widely used in crop protection. Recently, transgene-free procedures that were based on exogenous application of RNA molecules having the capacity to trigger RNAi have been reported. Yet, efficient delivery of such RNA molecules to plants and particularly to trees poses major technical challenges.

Replicating Potato spindle tuber viroid mediates de novo methylation of an intronic viroid sequence but no cleavage of the corresponding pre-mRNA.

In plants, Potato spindle tuber viroid (PSTVd) replication triggers post-transcriptional gene silencing (PTGS) and RNA-directed DNA methylation (RdDM) of homologous RNA and DNA sequences, respectively. PTGS predominantly occurs in the cytoplasm, but nuclear PTGS has been also reported. In this study, we investigated whether the nuclear replicating PSTVd is able to trigger nuclear PTGS.

Mapping of the exchangeable and dispensable domains of the RNA 2-encoded 2A(HP) protein of arabis mosaic nepovirus.

The N-terminal domains of the RNA 2-encoded 2A(HP) proteins of the arabis mosaic (ArMV) and grapevine fanleaf (GFLV) nepoviruses were shown to be highly variable and a hotspot for intra- and inter-species recombination events. Chimeric ArMV-NW clones in which the N-terminal domain of 2A(HP) or the entire 2A(HP) of GFLV isolates replaced the corresponding domains of ArMV retained their infectivity, showing that the 2A(HP) proteins of ArMV-NW and GFLV are exchangeable. ArMN-NW clones with deletions of the N-terminal, core, or C-terminal domains of the ArMV-NW 2A(HP) were infectious in Chenopodium quinoa although viral RNA (especially RNA 2) accumulated at reduced levels.

In vitro and in vivo evidence for differences in the protease activity of two arabis mosaic nepovirus isolates and their impact on the infectivity of chimeric cDNA clones.

Regulated processing of nepovirus polyproteins allows the release of mature proteins and intermediate polyproteins. Infectious cDNA clones of the mild NW isolate of arabis mosaic virus (ArMV) and chimeric clones incorporating RNA1 segments of Lv, a severe isolate, were generated. Clones containing the Lv X2-NTB cleavage site were not infectious unless the Lv protease was present.

Real-time multiplex RT-PCR for the simultaneous detection of the five main grapevine viruses.

A real-time multiplex RT-PCR has been developed for the simultaneous detection and identification of the major RNA viruses that infect grapevines (Grapevine fanleaf virus, Arabis mosaic virus, Grapevine leafroll-associated virus 1, Grapevine leafroll-associated virus 3 and Grapevine fleck virus). Serial dilutions of infected plant extracts were tested using the new method, and the results were compared with those obtained using a commercially available ELISA and real-time singleplex RT-PCR. The two real-time RT-PCR versions detected up to the same level of dilution and were at least 10,000 times more sensitive than the ELISA.

Characterization of proteinase cleavage sites in the N-terminal region of the RNA1-encoded polyprotein from Arabis mosaic virus (subgroup A nepovirus).

Arabis mosaic virus is a subgroup A nepovirus. The RNA1-encoded polyprotein (P1) contains the domains for the NTP-binding protein (NTB), VPg, proteinase (Pro) and polymerase at its C-terminus. Putative cleavage sites delineating these domains have been proposed.