Proteomic analysis of the potential mechanism of fading of aroma-related esters in "Nanguo" pears after long-term refrigeration

Low-temperature storage is a key method for delaying the ripening of "Nanguo" pears. However, the aroma of "Nanguo" pears fades after long-term refrigeration. We investigated the potential mechanism of fading of aroma in "Nanguo" pears by analyzing differentially expressed proteins in pears stored at room temperature, which had higher level of aromatic esters and those stored at low temperature, having lower esters. We observed that 293 kinds of proteins were down-regulated and 377 were up-regulated. Gene ontology analysis showed that proteins in the "catalytic activity," "metabolic process," "organelle," and "membrane" proteins were affected by low temperature. KEGG analysis showed that the differentially expressed proteins were involved in oxidative phosphorylation, carbon and fatty acid metabolism. Real-time PCR showed that transcription levels of nine selected genes correlated with differentially expressed proteins. The results revealed that the expression of potentially aroma-related proteins, which are important in further research on improving aroma quality of "Nanguo" pears. Practical applications "Nanguo" pears aroma is an important character for attracting consumers and many proteins are involved in the synthesis of aroma. However, their aroma is lost after cold storage and the quality of fruits is affected by low temperature. It is, therefore, of great significance to study the potential proteins that regulate the aroma of refrigerated "Nanguo" pears. In addition, the study results could provide basic and scientific data for the study of improving the aroma quality and genetic improvement of "Nanguo" pears.