Transcriptome analysis for key softening-related genes in 'Docteur Jules Guyot' pear (Pyrus communis L.)

The storage period of European pear (Pyrus communis L.) is prolonged at low temperature, but the pear softened quickly after shifting to room temperature. However, the molecular mechanisms that influence this process are unknown. In this study, 'Docteur Jules Guyot' pears were placed at room temperature (RT) and low temperature and then turned to room temperature (LR). The fruit firmness of 'Docteur Jules Guyot' under LR decreased faster than RT after moving from low temperature. The ethylene production rate, water-soluble pectin (WSP), ionicsoluble pectin (ISP) content, and pectin degradation enzyme activity of 'Docteur Jules Guyot' under LR increased faster than RT after moving from low temperature. RNA-seq of 'Docteur Jules Guyot' pear under different storage conditions was carried out, and 1018 genes were found to be negatively correlated with fruit firmness by the weighted gene coexpression network analysis (WGCNA) method. Then, 24 structural genes and transcription factors related to fruit softening were selected to verify the RNA-Seq results. The expression of all these selected genes increased significantly after LT storage. The fruit firmness, pectin content, and pectin degradation enzyme activity of 'Laiyang' pear did not change significantly under RT and LR storage conditions. The expression of LAX2, ARF19, EXP1, EXPA1, EXP3 and PG2 was upregulated in 'Docteur Jules Guyot' pear but downregulated in 'Laiyang' pear. These genes might play important roles in the softening process of European pear. This work laid the foundation for revealing the mechanisms of European pear fruit softening.