Transcriptome profiling reveals the candidate genes associated with aroma metabolites and emission of pear (Pyrus ussuriensis cv.)

Aroma is an important factor affecting pear fruit quality. However, the molecular basis for the development of aroma metabolites and their emission is poorly understood. Unripe 'Nanguoli' pear fruit has poor aroma, while the ripe fruit has an intense aroma, and calcium treatment can enhance the aroma, providing good material for transcriptome analysis. Digital gene expression (DGE) analysis of 'Nanguoli' fruit was performed at three important developmental stages, with and without calcium treatment, six libraries in total. Of the total number of mapped reads (11.4-13.6 million), an average of 69.81% could be mapped to the pear genome. A total of 10,776 differentially expressed genes between the poor aroma and intense aroma were categorized into 36 functional groups and 37 pathways according to GO and KEGG databases, respectively. Genes more highly expressed in the more aromatic fruit include some from the fatty acid pathway such as FAD, ADH, PDC, LOX, and lipase genes. Some transcription factors were identified with high correlation to aroma biosynthesis in pear. Also, ABA may play an important role in the calcium-triggered improvement of 'Nanguoli' aroma. In addition, candidate genes were verified with quantitative real-time PCR. (C) 2016 Elsevier B.V. All rights reserved.