Genome-wide identification and comparative analysis of the superoxide dismutase gene family in pear and their functions during fruit ripening

Superoxide dismutases (SODs), a key antioxidant enzyme family, are supposed to play an important role in the ripening of climactic fruit. However, information on SODs in pear, as well as their role in pear ripening process, is rudimentary. In this study, a comprehensive analysis was conducted on the characteristics of the SOD gene family in pear. In total, 11 PbrSOD genes were identified in pear (Pyrus bretschneideri) genome and were phylogenetically classified into five subgroups. Whole genome duplication (WGD)/segmental duplication was the main driving force for the expansion of the PbrSOD family genes, which harboured distinct types and numbers of conserved motifs and cis-acting elements in their promoters. During postharvest pear (Pyrus pyrifolia cv. 'Fengshui') ripening, the accumulation of oxidative stress was associated with a decrease in SOD activity. The expression patterns of 11 PbrSODs were distinct as postharvest pear fruit ripened, and the changes of some specific mRNAs were correlated with SOD activity. In combination with the results of the impact of postharvest treatments (ethrel and 1-MCP) on postharvest pear ripening process, PbrSODs gene expression and physio-chemical attributes, PbrCDS5 and PbrFSD1 were selected as the candidates involved in postharvest pear ripening.