Aberrant viral RNAs produced in infected plant cells serve as templates for the synthesis of dsRNAs. The derived virus-related small interfering RNAs (siRNA) mediate cleavage of viral RNAs by post-transcriptional gene silencing (PTGS), thus blocking virus multiplication. Here, we identified ASYMMETRIC LEAVES2 (AS2) as a new component of plant P body complex which mediates mRNA decapping and degradation. We found that AS2 promotes DCP2 decapping activity, accelerates mRNA turnover rate, inhibits siRNA accumulation and functions as an endogenous suppressor of PTGS. Consistent with these findings, as2 mutant plants are resistant to virus infection whereas AS2 over-expression plants are hypersensitive. The geminivirus nuclear shuttle protein BV1 protein, which shuttles between nuclei and cytoplasm, induces AS2 expression, causes nuclear exit of AS2 to activate DCP2 decapping activity and renders infected plants more sensitive to viruses. These principles of gene induction and shuttling of induced proteins to promote mRNA decapping in the cytosol may be used by viral pathogens to weaken antiviral defenses in host plants.
References
[1]
Pumplin N, Voinnet O (2013) RNA silencing suppression by plant pathogens: defence, counter-defence and counter-counter-defence. Nat Rev Microbiol 11: 745–760. doi: 10.1038/nrmicro3120. pmid:24129510
[2]
Vargason JM, Szittya G, Burgyan J, Hall TM (2003) Size selective recognition of siRNA by an RNA silencing suppressor. Cell 115: 799–811. pmid:14697199 doi: 10.1016/s0092-8674(03)00984-x
[3]
Zhang X, Yuan YR, Pei Y, Lin SS, Tuschl T, et al. (2006) Cucumber mosaic virus-encoded 2b suppressor inhibits Arabidopsis Argonaute1 cleavage activity to counter plant defense. Genes Dev 20: 3255–3268. pmid:17158744 doi: 10.1101/gad.1495506
[4]
Ying XB, Dong L, Zhu H, Duan CG, Du QS, et al. (2010) RNA-dependent RNA polymerase 1 from Nicotiana tabacum suppresses RNA silencing and enhances viral infection in Nicotiana benthamiana. Plant Cell 22: 1358–1372. doi: 10.1105/tpc.109.072058. pmid:20400679
[5]
Franks TM, Lykke-Andersen J (2008) The control of mRNA decapping and P-body formation. Mol Cell 32: 605–615. doi: 10.1016/j.molcel.2008.11.001. pmid:19061636
[6]
Arribas-Layton M, Wu D, Lykke-Andersen J, Song H (2013) Structural and functional control of the eukaryotic mRNA decapping machinery. Biochim Biophys Acta 1829: 580–589. doi: 10.1016/j.bbagrm.2012.12.006. pmid:23287066
[7]
Xu J, Yang JY, Niu QW, Chua NH (2006) Arabidopsis DCP2, DCP1, and VARICOSE form a decapping complex required for postembryonic development. Plant Cell 18: 3386–3398. pmid:17158604 doi: 10.1105/tpc.106.047605
[8]
Xu J, Chua NH (2009) Arabidopsis decapping 5 is required for mRNA decapping, P-body formation, and translational repression during postembryonic development. Plant Cell 21: 3270–3279. doi: 10.1105/tpc.109.070078. pmid:19855049
[9]
Gazzani S, Lawrenson T, Woodward C, Headon D, Sablowski R (2004) A link between mRNA turnover and RNA interference in Arabidopsis. Science 306: 1046–1048. pmid:15528448 doi: 10.1126/science.1101092
[10]
Thran M, Link K, Sonnewald U (2012) The Arabidopsis DCP2 gene is required for proper mRNA turnover and prevents transgene silencing in Arabidopsis. Plant J 72: 368–377. doi: 10.1111/j.1365-313X.2012.05066.x. pmid:22639932
[11]
Tsai WC, Richard EL (2014) Cytoplasmic RNA Granules and Viral Infection. Annual Review of Virology 1: 147–170. doi: 10.1146/annurev-virology-031413-085505
[12]
Hopkins KC, McLane LM, Maqbool T, Panda D, Gordesky-Gold B, et al. (2013) A genome-wide RNAi screen reveals that mRNA decapping restricts bunyaviral replication by limiting the pools of Dcp2-accessible targets for cap-snatching. Genes Dev 27: 1511–1525. doi: 10.1101/gad.215384.113. pmid:23824541
[13]
Zhou X (2013) Advances in understanding begomovirus satellites. Annu Rev Phytopathol 51: 357–381. doi: 10.1146/annurev-phyto-082712-102234. pmid:23915133
[14]
Gao S, Qu J, Chua NH, Ye J (2010) A new strain of Indian cassava mosaic virus causes a mosaic disease in the biodiesel crop Jatropha curcas. Arch Virol 155: 607–612. doi: 10.1007/s00705-010-0625-0. pmid:20224893
[15]
Fontes EP, Santos AA, Luz DF, Waclawovsky AJ, Chory J (2004) The geminivirus nuclear shuttle protein is a virulence factor that suppresses transmembrane receptor kinase activity. Genes Dev 18: 2545–2556. pmid:15489295 doi: 10.1101/gad.1245904
[16]
Hanley-Bowdoin L, Bejarano ER, Robertson D, Mansoor S (2013) Geminiviruses: masters at redirecting and reprogramming plant processes. Nat Rev Microbiol 11: 777–788. doi: 10.1038/nrmicro3117. pmid:24100361
[17]
Yang JY, Iwasaki M, Machida C, Machida Y, Zhou X, et al. (2008) betaC1, the pathogenicity factor of TYLCCNV, interacts with AS1 to alter leaf development and suppress selective jasmonic acid responses. Genes Dev 22: 2564–2577. doi: 10.1101/gad.1682208. pmid:18794352
[18]
Mourrain P, Beclin C, Elmayan T, Feuerbach F, Godon C, et al. (2000) Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance. Cell 101: 533–542. pmid:10850495 doi: 10.1016/s0092-8674(00)80863-6
[19]
Semiarti E, Ueno Y, Tsukaya H, Iwakawa H, Machida C, et al. (2001) The ASYMMETRIC LEAVES2 gene of Arabidopsis thaliana regulates formation of a symmetric lamina, establishment of venation and repression of meristem-related homeobox genes in leaves. Development 128: 1771–1783. pmid:11311158 doi: 10.1016/s0921-0423(01)80056-3
[20]
Iwakawa H, Ueno Y, Semiarti E, Onouchi H, Kojima S, et al. (2002) The ASYMMETRIC LEAVES2 gene of Arabidopsis thaliana, required for formation of a symmetric flat leaf lamina, encodes a member of a novel family of proteins characterized by cysteine repeats and a leucine zipper. Plant Cell Physiol 43: 467–478. pmid:12040093 doi: 10.1093/pcp/pcf077
[21]
Li H, Xu L, Wang H, Yuan Z, Cao X, et al. (2005) The Putative RNA-dependent RNA polymerase RDR6 acts synergistically with ASYMMETRIC LEAVES1 and 2 to repress BREVIPEDICELLUS and MicroRNA165/166 in Arabidopsis leaf development. Plant Cell 17: 2157–2171. pmid:16006579 doi: 10.1105/tpc.105.033449
[22]
Clough SJ, Bent AF (1998) Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J 16: 735–743. pmid:10069079 doi: 10.1046/j.1365-313x.1998.00343.x
[23]
Qu J, Ye J, Fang R (2007) Artificial microRNA-mediated virus resistance in plants. J Virol 81: 6690–6699. pmid:17344304 doi: 10.1128/jvi.02457-06
Li R, Weldegergis BT, Li J, Jung C, Qu J, et al. (2014) Virulence Factors of Geminivirus Interact with MYC2 to Subvert Plant Resistance and Promote Vector Performance. Plant Cell 26: 4991–5008. doi: 10.1105/tpc.114.133181. pmid:25490915
[26]
Ye J, Qu J, Mao HZ, Ma ZG, Rahman NE, et al. (2014) Engineering geminivirus resistance in Jatropha curcus. Biotechnol Biofuels 7: 149. doi: 10.1186/s13068-014-0149-z. pmid:25352912
[27]
Ye J, Qu J, Bui HT, Chua NH (2009) Rapid analysis of Jatropha curcas gene functions by virus-induced gene silencing. Plant Biotechnol J 7: 964–976. doi: 10.1111/j.1467-7652.2009.00457.x. pmid:19906247
[28]
Ye J, Liu P, Zhu C, Qu J, Wang X, et al. (2014) Identification of candidate genes JcARF19 and JcIAA9 associated with seed size traits in Jatropha. Funct Integr Genomics 14: 757–766. doi: 10.1007/s10142-014-0400-5. pmid:25228410
[29]
Muangsan N, Beclin C, Vaucheret H, Robertson D (2004) Geminivirus VIGS of endogenous genes requires SGS2/SDE1 and SGS3 and defines a new branch in the genetic pathway for silencing in plants. Plant J 38: 1004–1014. pmid:15165191 doi: 10.1111/j.1365-313x.2004.02103.x
[30]
Gimenez-Barcons M, Alves-Rodrigues I, Jungfleisch J, Van Wynsberghe PM, Ahlquist P, et al. (2013) The cellular decapping activators LSm1, Pat1, and Dhh1 control the ratio of subgenomic to genomic Flock House virus RNAs. J Virol 87: 6192–6200. doi: 10.1128/JVI.03327-12. pmid:23536653
[31]
Liu SW, Wyatt LS, Orandle MS, Minai M, Moss B (2014) The D10 decapping enzyme of vaccinia virus contributes to decay of cellular and viral mRNAs and to virulence in mice. J Virol 88: 202–211. doi: 10.1128/JVI.02426-13. pmid:24155373
[32]
Covarrubias S, Gaglia MM, Kumar GR, Wong W, Jackson AO, et al. (2011) Coordinated destruction of cellular messages in translation complexes by the gammaherpesvirus host shutoff factor and the mammalian exonuclease Xrn1. PLoS Pathog 7: e1002339. doi: 10.1371/journal.ppat.1002339. pmid:22046136
[33]
Li Y, Dai J, Song M, Fitzgerald-Bocarsly P, Kiledjian M (2012) Dcp2 decapping protein modulates mRNA stability of the critical interferon regulatory factor (IRF) IRF-7. Mol Cell Biol 32: 1164–1172. doi: 10.1128/MCB.06328-11. pmid:22252322
[34]
Moreno AB, Martinez de Alba AE, Bardou F, Crespi MD, Vaucheret H, et al. (2013) Cytoplasmic and nuclear quality control and turnover of single-stranded RNA modulate post-transcriptional gene silencing in plants. Nucleic Acids Res 41: 4699–4708. doi: 10.1093/nar/gkt152. pmid:23482394
[35]
Garcia D, Garcia S, Voinnet O (2014) Nonsense-mediated decay serves as a general viral restriction mechanism in plants. Cell Host Microbe 16: 391–402. doi: 10.1016/j.chom.2014.08.001. pmid:25155460
[36]
Gy I, Gasciolli V, Lauressergues D, Morel JB, Gombert J, et al. (2007) Arabidopsis FIERY1, XRN2, and XRN3 are endogenous RNA silencing suppressors. Plant Cell 19: 3451–3461. pmid:17993620 doi: 10.1105/tpc.107.055319
[37]
Zorzatto C, Machado JP, Lopes KV, Nascimento KJ, Pereira WA, et al. (2015) NIK1-mediated translation suppression functions as a plant antiviral immunity mechanism. Nature: doi: 10.1038/nature14171. pmid:25707794
[38]
Rajamaki ML, Streng J, Valkonen JP (2014) Silencing Suppressor Protein VPg of a Potyvirus Interacts With the Plant Silencing-Related Protein SGS3. Mol Plant Microbe Interact 27: 1199–1210. doi: 10.1094/MPMI-04-14-0109-R. pmid:25099340
[39]
Okano Y, Senshu H, Hashimoto M, Neriya Y, Netsu O, et al. (2014) In Planta Recognition of a Double-Stranded RNA Synthesis Protein Complex by a Potexviral RNA Silencing Suppressor. Plant Cell 26: 2168–2183. pmid:24879427 doi: 10.1105/tpc.113.120535
[40]
Guo H, Song X, Xie C, Huo Y, Zhang F, et al. (2013) Rice yellow stunt rhabdovirus protein 6 suppresses systemic RNA silencing by blocking RDR6-mediated secondary siRNA synthesis. Mol Plant Microbe Interact 26: 927–936. doi: 10.1094/MPMI-02-13-0040-R. pmid:23634838
[41]
Du Z, Xiao D, Wu J, Jia D, Yuan Z, et al. (2011) p2 of rice stripe virus (RSV) interacts with OsSGS3 and is a silencing suppressor. Mol Plant Pathol 12: 808–814. doi: 10.1111/j.1364-3703.2011.00716.x. pmid:21726383
[42]
Glick E, Zrachya A, Levy Y, Mett A, Gidoni D, et al. (2008) Interaction with host SGS3 is required for suppression of RNA silencing by tomato yellow leaf curl virus V2 protein. Proc Natl Acad Sci U S A 105: 157–161. doi: 10.1073/pnas.0709036105. pmid:18165314
