title: Comparative analysis among the small RNA populations of source, sink and conductive tissues in two different plant-virus pathosystems.
abstract: BACKGROUND
  In plants, RNA silencing plays a fundamental role as defence mechanism against viruses. During last years deep-sequencing technology has allowed to analyze the sRNA profile of a large variety of virus-infected tissues. Nevertheless, the majority of these studies have been restricted to a unique tissue and no comparative analysis between phloem and source/sink tissues has been conducted. In the present work, we compared the sRNA populations of source, sink and conductive (phloem) tissues in two different plant virus pathosystems. We chose two cucurbit species infected with two viruses very different in genome organization and replication strategy; Melon necrotic spot virus (MNSV) and Prunus necrotic ringspot virus (PNRSV).
  
  
  RESULTS
  Our findings showed, in both systems, an increase of the 21-nt total sRNAs together with a decrease of those with a size of 24-nt in all the infected tissues, except for the phloem where the ratio of 21/24-nt sRNA species remained constant. Comparing the vsRNAs, both PNRSV- and MNSV-infected plants share the same vsRNA size distribution in all the analyzed tissues. Similar accumulation levels of sense and antisense vsRNAs were observed in both systems except for roots that showed a prevalence of (+) vsRNAs in both pathosystems. Additionally, the presence of overrepresented discrete sites along the viral genome, hot spots, were identified and validated by stem-loop RT-PCR. Despite that in PNRSV-infected plants the presence of vsRNAs was scarce both viruses modulated the host sRNA profile.
  
  
  CONCLUSIONS
  We compare for the first time the sRNA profile of four different tissues, including source, sink and conductive (phloem) tissues, in two plant-virus pathosystems. Our results indicate that antiviral silencing machinery in melon and cucumber acts mainly through DCL4. Upon infection, the total sRNA pattern in phloem remains unchanged in contrast to the rest of the analyzed tissues indicating a certain tissue-tropism to this polulation. Independently of the accumulation level of the vsRNAs both viruses were able to modulate the host sRNA pattern.
authors.affiliation: Instituto de Biología Celular y Molecular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Campus UPV, CPI 8E, Avda. Ingeniero Fausto Elio s/n, Valencia, 46022, Spain. carhergor@gmail.com.
authors.forename: Mari Carmen
authors.initials: MC
authors.lastname: Herranz
authors.affiliation: Instituto de Biología Celular y Molecular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Campus UPV, CPI 8E, Avda. Ingeniero Fausto Elio s/n, Valencia, 46022, Spain. janavarr@ibmcp.upv.es.
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Navarro
authors.affiliation: Instituto de Biología Celular y Molecular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Campus UPV, CPI 8E, Avda. Ingeniero Fausto Elio s/n, Valencia, 46022, Spain. evelien_sommen@hotmail.com.
authors.forename: Evelien
authors.initials: E
authors.lastname: Sommen
authors.affiliation: Instituto de Biología Celular y Molecular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Campus UPV, CPI 8E, Avda. Ingeniero Fausto Elio s/n, Valencia, 46022, Spain. vpallas@ibmcp.upv.es.
authors.forename: Vicente
authors.initials: V
authors.lastname: Pallas
mesh_terms: D018553:Cucumis sativus / Q000821:virology; D019662:Cucurbitaceae / Q000821:virology; D015967:Gene Expression Regulation, Viral; D016679:Genome, Viral; D059014:High-Throughput Nucleotide Sequencing; D052585:Phloem / Q000821:virology; D010942:Plant Viruses / Q000235:genetics* / Q000472:pathogenicity; D012313:RNA / Q000096:biosynthesis / Q000145:classification / Q000235:genetics*
chemical_list: D012313:RNA