Physiological and transcriptomic analysis of 'Whangkeumbae' pear core browning during low-temperature storage.

Core browning of 'Whangkeumbae' pear has become an urgent problem in the Chinese pear industry, which often appears after several months of low-temperature storage. However, little is known regarding the crosstalk between physiology and molecular mechanisms regulating the core browning process of the pear. In this study, the physiological and genetic responses of the core were identified during storage. The results showed that the malonyldialdehyde (MDA) content, electrolyte leakage, hydrogen peroxide (H2O2) content and superoxide anion (O2·-) production rate progressively increased during the browning process. Polyphenoloxidase (PPO), phospholipase D (PLD) and lipoxygenase (LOX) activity initially slightly increased but then sharply increased during the later storage stage. A total of 33,265 unigenes was generated via high-throughput sequencing, and 5121 differentially expressed genes (DEGs) were identified. These DEGs were functionally annotated and some core browning-related DEGs involved in the redox reaction, membrane lipid metabolism and enzymatic browning were also determined. We found that the changes in the gene expression accorded with the physiological variation, indicating the close crosstalk between physiological and genetic response during storage. Our study provides a basis for future research on the core browning mechanism during pear storage.