Hibiscus chlorotic ringspot virus coat protein inhibits trans-acting small interfering RNA biogenesis in Arabidopsis

Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117545 Singapore.
Journal of General Virology (Impact Factor: 3.18). 10/2008; 89(Pt 9):2349-58. DOI: 10.1099/vir.0.2008/002170-0
Source: PubMed


Many plant and animal viruses have evolved suppressor proteins to block host RNA silencing at various stages of the RNA silencing pathways. Hibiscus chlorotic ringspot virus (HCRSV) coat protein (CP) is capable of suppressing the transiently expressed sense-RNA-induced post-transcriptional gene silencing (PTGS) in Nicotiana benthamiana. Here, constitutively expressed HCRSV CP from transgenic Arabidopsis was found to be able to rescue expression of the silenced GUS transgene. The HCRSV CP-transgenic Arabidopsis (line CP6) displayed several developmental abnormalities: elongated, downward curled leaves and a lack of coordination between stamen and carpel, resulting in reduced seed set. These abnormalities are similar to those observed in mutations of the genes of Arabidopsis RNA-dependent polymerase 6 (rdr6), suppressor of gene silencing 3 (sgs3), ZIPPY (zip) and dicer-like 4 (dcl4). The accumulation of microRNA (miRNA) miR173 remained stable; however, the downstream trans-acting small interfering RNA (ta-siRNA) siR255 was greatly reduced. Real-time PCR analysis showed that expression of the ta-siRNA-targeted At4g29770, At5g18040, PPR and ARF3 genes increased significantly, especially in the inflorescences. Genetic crossing of CP6 with an amplicon-silenced line (containing a potato virus X-green fluorescent protein transgene under the control of the 35S cauliflower mosaic virus promoter) suggested that HCRSV CP probably interfered with gene silencing at a step after RDR6. The reduced accumulation of ta-siRNA might result from the interference of HCRSV CP with Dicer-like protein(s), responsible for the generation of dsRNA in ta-siRNA biogenesis.

Download full-text


Available from: Sek-Man Wong, May 05, 2015
  • Source
    • "A biologically active cDNA clone of HCRSV p223 has been obtained previously [3]. The HCRSV CP (p38) [3] is a gene silencing suppressor [12]. In addition, p27 and its other in-frame isoforms (p25 and p22.5) affect symptom expression and potentiate Carmoviruses movement in kenaf (Hibiscus cannabinus L.) [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The p23 is a unique protein in the Hibiscus chlorotic ringspot virus which belongs to Family Tombusviridae Genus Carmovirus. Our previous results showed that the p23 is indispensable for host-specific replication and is localized in the nucleus with a novel nuclear localization signal. To investigate additional function(s) of p23, mutations of basic amino acids lysine (K), arginine (R) and histidine (H) that abolish its nuclear localization, were introduced into a biologically active full-length cDNA clone p223 of HCRSV for testing its effects on virus replication and virus movement in vivo. Primer-specific reverse transcription-PCR was conducted to detect gene transcript level of p23 and viral coat protein separately. Virus replication and its coat protein expression were detected by fluorescent in situ hybridization and Western blot, respectively. The effect of p23 was further confirmed by using artificial microRNA inoculation-mediated silencing. Results showed that the two mutants were able to replicate in protoplasts but unable to move from inoculated leaves to newly emerged leaves. Both the p23 and the CP genes of HCRSV were detected in the newly emerged leaves of infected plants but CP was not detected by Western blot and no symptom was observed on those leaves at 19 days post inoculation. This study demonstrates that when p23 is prevented from entering the nucleus, it results in restriction of virus long distance movement which in turn abrogates symptom expression in the newly emerged leaves. We conclude that the p23 protein of HCRSV is required for virus long distance movement.
    Full-text · Article · Sep 2013 · PLoS ONE
  • Source
    • "The alteration of the ta-siRNA pathway has been reported in many plant–virus combinations and has been suggested to be involved in symptom development (Lacombe et al., 2010; Meng et al., 2008; Shivaprasad et al., 2008). In this study, we found that the ta-siRNA pathway may be affected in RSV-infected rice. "

    Full-text · Article · Jan 2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: The uniaxial tester is an instrument where powder samples can be consolidated uniaxially in a die at different stress levels. After consolidation the die is removed and the axial compressive strength is measured. By repeating the procedure at different consolidation stress levels, the compressive strength is determined as a function of the consolidation stress, indicating the flow properties of the powder. Advantages of this method are that it is relatively simple to use, and it has a reproducibility that is better than most other methods. In the work to further improve the reproducibility, it has been found that the procedure of filling the die is very important. Three different procedures therefore have been tested, including one using vibration to pack the sample during filling of the die. Although the procedure using vibrations so far has not improved the reproducibility, it may still reduce the operator dependency. Results of some preliminary work to develop an improved filling procedure are reported on here.
    No preview · Article · Dec 2001 · Handbook of Powder Technology
Show more