Molecular cloning and gene expression differences of the anthocyanin biosynthesis-related genes in the red/green skin color mutant of pear (Pyrus communis L.)

To reveal the molecular mechanisms that led to the red/green color mutation of pear between the cultivar 'Early red Doyenne du Comice' and its green variant strain, the full-length cDNA of the seven anthocyanin biosynthesis genes (PAL, CHS, CHI, DFR, F3H, ANS, UFGT) was cloned in both cultivars. The accession number has been submitted to National Center for Biotechnology Information (NCBI) as KC460392, KC460393, KC460394, KC460395, KC460396, KC460397, and KC460398, respectively. However, there was no sequence difference between the color mutants, which means that the skin color change was not caused by mutation of any of these genes. Meanwhile, the expression levels of these seven genes were examined by quantitative real-time PCR (qRT-PCR). Results showed that most of the structural genes were up-regulated in the red-skinned cultivar during fruit development, but the CHI and UFGT genes were highly expressed only at an early stage. The expression levels of the transcription factors MYB10, bHLH, and WD40 were also investigated by qRT-PCR, and the MYB10 gene was found to be expressed at significantly higher levels in the red variety than in the green mutant at the early stage, while the expression levels of bHLH and WD40 were higher at a later stage. These data indicate that the expression difference of structural genes in the anthocyanin biosynthesis pathway led to the skin color change of the mutant. However, MYB10, bHLH, and WD40 do not appear to be the key transcription factors that regulate the biosynthesis of anthocyanin and determine the red/green color mutant.