Tanscriptome Analysis of Pear Fruit Development Revealing Different Gene Expression Pattern of Cultivated Species

Transcriptome of five different cultivars, ‘Hosui’, ‘Yali’, ‘Kuerlexiangli’, ‘Nanguoli’ and ‘Red Clapp's Favorite’, which represent all five cultivated species of pear, were sequenced at seven key periods from the stage of fruit setting to post-harvest storage. A total of 33,136 mapping genes were analyzed based on the RNA-seq single end data. In the cluster models, a large amount of genes were found expressed with the pattern of steady decreasing in four Asian cultivars, while European pear of ‘Red Clapp's Favorite’ showed a gradually decreasing tendency of gene expression. ‘Red Clapp's Favorite’ and ‘Nanguoli’ belong to the post-ripening types, with more vigorous and higher proportion of up-regulated genes after fruit harvesting stage. Gene functional analysis was carried out between post-ripening and non-post-ripening cultivars and revealed high differences in cell proliferation. Furthermore, fruit quality related characteristics, including hormones, stone cells, sugar and acid, were analyzed based on the differently expressed genes analysis. In addition, co-expression analysis revealed the relationship of genes in different biological pathway, such as sugar and anthocyanin synthesis. In conclusion, RNA-seq based gene expression pattern contributes to the deep understanding of pear fruit development.