Characterization of the glutathione S-transferase (GST) gene family in Pyrus bretschneideri and their expression pattern upon superficial scald development

Glutathione S-transferases (GSTs) proposedly play a crucial role in the development of superficial scald in pear fruit; however, the specific member from pear GST gene family, which plays an important role in this process, has not been identified until recently. In this study, a total of 62 GST family genes were identified in Pyrus bretschneideri genome, which were distributed across the 14 chromosomes and 8 scaffolds with an uneven distribution. They could be categorized into eight classes based on phylogenetic analysis, and WGD/segmental duplication mainly drove their expansion. The expression of PbrGSTs in 'Yali' pear fruit was tissue-specific. In accompany with superficial scald development was the accumulation of reactive oxygen species (ROS) accumulation and loss of ascorbic acid (AsA) in the pericarp of 'Yali' pear. Of 47 PbrGSTs detected in the pericarp, the transcription of 25 members were enhanced upon the development of superficial scald, while three in dehydroascorbate reductase (DHAR) class were downregulated in association with lower DHAR activity. In combination with the results of the impact of 1-MCP and MHO fumigation on the expression profile of PbrGSTs, PbrDHAR1, PbrDHAR2 and PbrDHAR4 were selected as the candidate gene involved in superficial scald development.