TMV-Cg impact on plant RNA exosome complex is involved in antiviral PTGS and symptoms development

GABRIELA CONTI; OTTOLINI, AGUSTÍN; ANDREA LAURA VENTURUZZI; DIEGO ZAVALLO; SEBASTIAN ASURMENDI

Quilmes

Congreso; II Reunión Argentina de Biología de ARNs no codificantes; 2018

The RNA exosome complex is a versatile RNA degradation machinery involved in several aspects of RNA regulation and quality control, including responses to environmental cues and development. In plants, it is antagonistically related to post-transcriptional gene silencing, a very well-studied defense pathway against viral infections. Previous results from our group showed that the expression level of several RNA exosome components are upregulated as a result of TMV infections in tobacco plants. When individual RNA exosome components were down-regulated by means of VIGS, viral accumulation and symptoms development were reduced in agreement with a post-transcriptional gene silencing enhancement. Here we analyzed the expression levels of a set of RNA exosome complex transcripts, including core subunits and cytoplasmic and nuclear cofactors in TMV-Cg infected Arabidopsis thaliana (7dpi and 14dpi) compared to mock infected control plants. We observed a generalized downregulation of RNA exosome transcripts, as opposed to results observed in tobacco plants. We also challenged Arabidopsis knock-down mutants for a set of RNA exosome components (rrp4, mtr4, hen2 and ski3) against TMV-Cg viral strain in order to examine the impact on defense responses and symptoms development. Results showed that at late stages of infection (14dpi) the symptoms were more severe in mutant plants. Surprisingly, despite the symptomatology observed, viral titers were lower and the amount of small RNAs directed against TMV-Cg Coat Protein (sCP-Cg) were higher in mutant plants, suggesting that antiviral PTGS could be enhanced in the former. Finally, we challenged tobacco plants against TMV-Cg viral strain and we observed a strong upregulation of RNA decay transcripts as previously shown for TMV infection, indicating that this modulation is a fine tuned response seemingly orchestrated along host-pathogen co-evolution. The alteration of the RNA exosome complex is emerging as an interesting pathway modulated during viral infections that could be associated to defense or counter-defense strategies in a host-dependent manner and could also be implicated in the development of disease symptoms.