Transcriptomic responses of strawberry fruits exposed to postharvest treatments with Plasma-Activated Fog.

Plasma-Activated Fog (PAF) is a new promising technology for fruit decontamination against postharvest fungal pathogens. It consists of an aerosol made by droplets of water, nebulized by the effluent gases of a plasma discharge. In this work, PAF was generated via dielectric barrier volume discharge in a jet-like configuration and used in postharvest applications on strawberry fruits reducing significantly the incidence of rots. To study the effects of treatments on fruits, transcriptomic changes induced by PAF were investigated through RNA-Seq analysis. Total RNA was extracted from strawberries exposed to 10 min of PAF treatment and from the untreated control fruits, at 6 h and 24 h after treatment, and used for Illumina sequencing. A total of 524,3 Gb of sequencing data (2x150 bp reads) from twelve cDNA libraries were generated. By comparing the expression values in treated versus untreated samples, a total of 1,611 differentially expressed genes (DEGs) were identified as significantly modulated (FC≥ |2| and FDR≤ 0.05) after PAF treatment. Genes involved in the ethylene biosynthetic process (e.g., 1-aminocyclopropane-1-carboxylate oxidase), fruit ripening and sweetness (e.g, genes coding for miraculin-like proteins which are glycoproteins with taste-modifying activity that converts sourness into sweetness), plant responses to biotic and abiotic stresses (e.g., L-type lectin-domain containing receptor kinase, and PR-4-like genes), and auxin homeostasis and signalling were significantly up-regulated in treated versus untreated fruits. These findings demonstrate that PAF treatments activated fruit defence responses suggesting an increased resilience in the treated fruits that may affect their shelf-life and quality.