The transcriptional mechanism responding to air particulate matter in Laurus nobilis (L.)

Air levels of particulate matter (PM) are dangerously increasing in urban environment due to high levels of industrialization. The use of plants to reduce pollutants is well-known although molecular mechanisms underlying this phenomenon have been scarcely investigated. The aim of this work was to shed lights into the molecular physiological responses of leaves of a typical plant ornamental species (Laurus nobilis L.), to identify key PM-modulated genes of early leaf responses and to optimize phylloremediation strategies in polluted areas. The transcriptome and the PM accumulation in leaf tissues were analysed in plants grown in pots for three months under two different areas: rural and traffic. Differentially expressed genes in common between different pairwise comparisons were highly effective in discriminating leaves at high PM levels after three months of exposure. Thirty of these genes showed contrasting trend of expression between rural and traffic conditions. Higher PM levels highlighted significant repression of genes and gene set categories involved in cell wall and membrane modification. In addition, a repression of genes involved in photosynthesis reactions, glycolysis, gluconeogenesis, TCA, fermentation was observed. Some key members of C2H2, WRKYs and CCAAT-HAP2 were induced as well as downstream defense response genes. The results allowed to develop a general model of gene regulatory networks in response to particulate matter in plants and innovative biotechnological approaches for phylloremediation strategies.