7.23

Proceedings of the 57th Italian Society of Agricultural Genetics Annual Congress
Foggia, Italy – 16/19 September, 2013
ISBN 978-88-904570-3-6
Poster Communication Abstract – 7.23
EXPLORING RNA SILENCING AS A PATHOGENICITY FACTOR IN
PLANT - VIRUS INTERACTIONS
FINETTI-SIALER M.M.*, CATALANO D.*, CILLO F.**
*) Istituto di Genetica Vegetale, onsiglio Nazionale delle Ricerche, Via Amendola, 70126 Bari
(Italy)
**) Istituto di Virologia Vegetale, Consiglio Nazionale delle Ricerche, Via Amendola, 70126 Bari
(Italy)
RNA silencing, biotic stresses, Solanum lycopersicum, virus, genomics
RNA silencing (RS) is a conserved eukaryotic mechanism acting as anti-viral immune system
in plants. Small interfering RNAs (siRNAs) are RS effectors accumulating in virus-infected tissues
as immune system components, providing target specificity for post-transcriptional degradation of
invading RNAs. Virus-derived siRNAs (vsiRNAs, 21-24 nt) are abundant in infected plants, with
certain regions (“hot spots”) more represented than others.
Two isolates of Potato virus Y (PVY), PVYC-to and PVY-SON41, yield very different
disease phenotypes on tomato (Solanum lycopersicum), the former inducing leaf distortions, the
latter mild symptoms. We applied in silico and molecular approaches to identify PVY vsiRNAs
suppressing host mRNAs by sequence complementarity and RS-based suppression, inducing
dysfunctional processes upon infection. Aim was to explore differential expression of host-targeting
vsiRNA, as responsible of isolates differences.
A computational pipeline retrieved 21nt vsiRNAs from PVY isolates, complementary to
predicted mRNAs (Solgenomics, ITAG2.3). Two PVYC-to genome regions showed specific
secondary structures absent in PVY-SON41, accounting for vsiRNAs accumulation. Two tomato
transcript lists were obtained, perfectly or imperfectly (one or two mismatches) complementary to
vsiRNA computed for either PVY isolates, putative targets of vsiRNA-driven RS suppression.
Targets common to both isolates were discarded, leaving a gene list representing only PVYC-to
targets. Quantitative RT-PCR of transcription factors (e.g. NAC, MYB, TCP, HD-ZIP, MADS-box
families) active in leaf development and morphogenesis showed differential expression upon
PVYC-to and PVY-SON41 infections. Lower isolate-specific mRNA accumulation suggested RSdriven post-transcriptional regulation, confirming a link between symptoms and vsiRNAs-mediated
RS. Results from vsiRNAs deep sequencing from infected leaves are also discussed.