Mesocarp RNA-Seq analysis of mango (Mangifera indica L.) identify quarantine postharvest treatment effects on gene expression

Quarantine measures to prevent insect dispersion include modified atmospheres or hot water treatment (HWT) for mango. The effects of HWT on mango “Ataulfo” at mature-green and ripe stages on gene expression were evaluated by RNA-seq. 27,629 ORF were annotated according to the non-redundant database and most of the changes in gene expression due to the HWT occurred at the mature-green stage with 903 differentially expressed genes (Log2 fold-change ≥ 4, FDR < 0.05). Up-regulated transcripts in HWT fruit have roles in transcription regulation, carbohydrate metabolism, defense response, cell wall modification, intracellular signal transduction, stress and heat shock response, response to oxidative stress, lipid metabolic process, and transferase activity. Gene Ontology enrichment analysis in molecular function level showed that HWT stimulated gene expression of hydrolase activity and these transcripts belong to sucrose, starch, and cell wall polysaccharide metabolic processes. Among them, putative genes for pectin methylesterases, pectate lyases, polygalacturonases, β-galactosidases and rhamnogalacturonan lyases were identified. As shown by RT-qPCR the expression of five of these genes was up-regulated due to the HWT and the activities of polygalacturonase, pectate lyase and beta-galactosidase were induced by HWT. Transcripts down-regulated by the HWT include those that code for putative cell surface adhesion proteins, ethylene responsive transcription factors, arabinogalactan proteins, response to stress, cytochrome p450, kinases for defense-related processes, fatty acid metabolism, flavonoid and volatile esters biosynthesis, and genes associated with photosynthesis. The HWT effects on gene expression are more pronounced few days after treatment and the metabolism is dramatically affected beyond the heat shock response.