Identification of miRNAs involved in SO2 preservation in Vitis vinifera L. by deep sequencing

Abstract

Table grapes are a major fruits worldwide but are highly susceptible to decay during storage. Sulphur dioxide (SO2) can help to maintain the quality of postharvest grapes. However, the molecular mechanism on how grape berries respond to SO2 remains to be elucidated. MicroRNAs (miRNAs) are a family of non-coding small RNAs that play important regulatory roles in various biological processes. In this study, Illumina sequencing technology was used to sequence seven small RNA libraries constructed from ‘Muscat Hamburg’ grape berries treated with SO2 (under commercial conditions) and the control. A total of 148 known miRNAs and 49 putative novel miRNAs were identified from all libraries. Sixty-one miRNAs (54 known miRNAs and 7 novel miRNAs) were differentially expressed in response to SO2 fumigation. Moreover, differentially expressed miRNAs (DEMs) were predicted to target a total of 543 annotated genes. Importantly, some targets were annotated as transcription factors, and numerous predicted target genes belonged to functional proteins. Quantitative real time PCR (qPCR) and Pearson’s correlation coefficient analysis validated the negative correlation expression patterns between seven DEMs (6 known miRNAs and 1 novel miRNA) and their corresponding target genes. Furthermore, these DEMs could negatively regulate their target genes associated with fruit softening, membrane lipid peroxidation, rachis browning and secondary metabolism, contributing to delaying fruit physiological senescence and resisting pathogen infection during storage, thereby maintaining fruit quality. This study provides new insight into molecular mechanism of SO2 preservation for fruit storage.