Identification and comparative analysis of the MCU gene family in pear and its functions during fruit ripening

Mitochondrial calcium uniporter (MCU) plays an important role in cell senescence and aging in mammals. However, the function of MCU homologs during the ripening and senescence of postharvest fruit had not been characterized until recently. In this study, a comprehensive study was conducted on the characteristics of the MCU family genes in the pear genome. In total, seven PbrMCU genes were identified and classified into two subgroups. Whole-genome duplication (WGD)/segmental duplication is the main driving force behind their expansion. The genes contained various conserved motifs and cis-acting elements, and the correspondent proteins possessed a serial of conserved motifs. A total of six PbrMCUs with diverse expression patterns were detected as the pear fruit ripened. Following the results of the impact of postharvest treatments (ethrel and 1-methylcyclopropene) and transient overexpression of 1-aminocyclopropane-1-carboxylate oxidase 1 gene (PbrACO1), the candidate genes PbrMCU3, PbrMCU4, and PbrMCU7 were determined to be involved in pear ripening. Moreover, the response of mitochondrial calcium uptake 1 (PbrMICU1) transcription to the postharvest treatments was similar to that of PbrMCU4.