Effect of Paper-Bagging on Apple Skin Patterning Associated with MdMYB10 Promoter Methylation

Abstract

Paper-bagging is an efficient method to maximize apple skin color, but a relationship between this technique and fruit skin patterning has not been demonstrated. Here, the ‘Fuji’ fruit with red-striped skin changed to red-blushed skin under re-exposure to light after bag treatment. Higher expression of MdMYB10, a transcription factor that regulates anthocyanin biosynthesis in apples, correlated with increased anthocyanin concentration in bag removal fruit. At the mature stage, a comparison of methylation status in the MdMYB10 promoter revealed that the methylation level in the region from −2585 to −2117 bp was reduced in bag removal fruit, especially for CHG context. It can be regulated by the downregulated expression of DNA methyltransferases such as MdMET, MdCMT, and MdDRM. Our results suggest that the bag removal treatment in this cultivar causes a change in skin patterning from striped to blushed pigmentation by inducing DNA demethylation of MdMYB10.

Genetic and epigenetic control of the plant metabolome

“…The remaining DNA after digestion can be amplified by PCR for the region of interest. McrBC treatment followed by PCR is commonly used for assessing the cytosine methylation state of target DNA regions [48, 56–61]. The affinity enrichment method utilises anti‐methylcytosine antibodies as in Methylated DNA immunoprecipitation (MeDIP) or methyl‐CpG‐binding domain (MBD) proteins as in MBDCap‐seq.…”

“…While a significant reduction of cytosine methylation was observed in the promoter of MdMYB1 of ‘Granny Smith’ after bag removal, cytosine methylation remained unchanged in ‘Golden Delicious’ [187]. Skin pattern change after bagging treatment was also attributed to differential cytosine methylation upstream of MdMYB10 in the apple variety ‘Fuji’ [61] (Figure 4E).…”

Multilevel regulation of anthocyanin-promoting R2R3-MYB transcription factors in plants

“…Similarly, REPRESSOR OF SILENCING 1 (ROS1), which encodes a DNA glycosylase DEMETER (DME) family protein, promotes demethylation of MdMYB10 in apple leaves at low temperature, demonstrating that demethylation of R2R3-MYBs is involved in anthocyanin accumulation induced by low temperature ( Yu L. et al, 2022 ). Some fruits such as apple and pear are placed in paper bags to accumulate more anthocyanins in their fruit skin after fruits are removed from the bags ( Bai et al, 2017 ; Cho et al, 2022 ). This accumulation in apples is associated with epigenetic changes in the promoter of MdMYB10 and MdMYB1 .…”

“…This accumulation in apples is associated with epigenetic changes in the promoter of MdMYB10 and MdMYB1 . The bag removal treatment causes demethylation of MdMYB10 , which promotes a blush color in the fruit skin, in part due to the downregulated expression of genes for DNA methyltransferases such as MdMET, MdCMT, and MdDRM ( Cho et al, 2022 ). The CG-type methylation level of the MdMYB10 promoter in the blushed skin was significantly lower than in red-striped skin, indicating the importance of differential DNA methylation levels in the promoter regions of key MYB transcription factors on stripe phenotypes ( Jia et al, 2020 ).…”