454 sequencing to assess the differential expression of genes due to ozone stress in Viburnum lantana L.

Individuals of the shrub species Viburnum lantana L. (wayfaring tree) treated with ozone (60 ppb for 45 days, 5 hours per day) (= treatment) or maintained in filtered air (= control) were analysed through suppression subtractive hybridization (SSH) in order to assess the main differences of induced (I) and repressed (R) libraries, representing the response of plants at a biological, cellular and molecular level. Biomolecular procedures consisted in: RNA extraction; PCR select (SSH); 454 cDNA library sequencing. A total of 38,800 and 12,495 high quality reads were assembled (Newbler and CAP3 softwares) after filtering, for the induced and repressed libraries, resulting in a total of 543 and 705 UniGenes, respectively. Functional annotation and gene ontology assignment were used to define the different relevance of gene ontology (GO) categories in the libraries. Results show an enrichment of GO categories involved in the defense to oxidative stress for the induced library, with an increase in glutathione (GSH), thioredoxin-1 (Trx1), and heat shock proteins (HSP). On the contrary, the GO categories involved in carbon utilization and photosynthesis (light harvesting complexes) were repressed in ozone exposed plants of V. Lantana.