Transcriptome of wax apple (Syzygium samarangense) provides insights into nitric oxide-induced delays of postharvest cottony softening

Wax apple (Syzygium samarangense) is an important tropical fruit crop in Southeast Asia. The rapid cottony softening that occurs after harvest significantly influences the nutrition, flavour and market value of the fruit. Nitric oxide (NO) fumigation has been used to delay the cottony softening process in wax apple; however, the underlying molecular mechanisms at the gene regulation level are poorly understood. In this study, we first sequenced and de novo assembled the wax apple fruit transcriptome using the Illumina Hiseq2000 platform. Meanwhile, we compared the gene expression profiles between NO treatment and control wax apples at different postharvest storage periods using digital gene expression (DGE). This study developed transcriptome data resources for wax apple fruit and provided a foundation for understanding the molecular mechanisms underlying NO-induced cottony softening delay. RNA-Seq generated 5.9 G raw data, which were then de novo assembled into 54,536 unigenes with an N50 length of 1724 bp. 21,433 Unigenes were annotated by the nr database and 3044 were successfully annotated by all databases. The dynamic analysis of the gene expression patterns suggested that NO-induced delays of cottony softening occur in wax apple via the regulation of cell wall degradation, carbohydrate metabolism, oxidation-reduction and plant hormone signal transduction pathways. These results provide a reference for the study of complicated metabolism in non-model perennial species.