How does particulate matter affect plant transcriptome and microbiome?

Phylloremediation for the reduction of air particulate matter (PM) is an interesting opportunity to significantly contribute to improve the air quality of urban environment. The aim of this study was to: 1) gain insight into the gene regulatory networks modulating leaf responses to polluted air, 2) identify possible changes in the leaf microbiome due to particulate matter in the real urban environment. The leaf transcriptome and microbiome were analyzed for Photinia x fraseri L. plants cultivated for three months in pots in two close-by areas under different levels of air PMs (low and high). PCA and heat map analysis showed that 28 differentially expressed genes in common between the three pairwise comparisons were able to clearly discriminate plants under higher PM levels. The pollutants were mainly sensed by plants through a restructuring modification of cell wall and membrane due to the main repression of lipid desaturases. In addition, high PMs showed a clear repression of genes belonging to primary metabolism pathways involved in C assimilation. Microbiome analysis showed no significant changes in taxonomic diversity indexes for the bacterial communities, whereas fungi belonging to the genera Epicoccum and Dioszegia were differently affected by the different exposure to PM levels. A model of transcriptional regulation to air PMs in plants has been proposed.