The Methylation of the PcMYB10 Promoter Is Associated with Green-Skinned Sport in Max Red Bartlett Pear    

Abstract

Varieties of the European pear (Pyrus communis) can produce trees with both red-and green-skinned fruits, such as the Max Red Bartlett (MRB) variety, although little is known about the mechanism behind this differential pigmentation. In this study, we investigated the pigmentation of MRB and its green-skinned sport (MRB-G). The results suggest that a reduction in anthocyanin concentration causes the MRB-G sport. Transcript levels of PcUFGT (for UDP-glucose:flavonoid 3-O-glucosyltransferase), the key structural gene in anthocyanin biosynthesis, paralleled the change of anthocyanin concentration in both MRB and MRB-G fruit. We cloned the PcMYB10 gene, a transcription factor associated with the promoter of PcUFGT. An investigation of the 2-kb region upstream of the ATG translation start site of PcMYB10 showed the regions 2604 to 2911 bp and 21,218 to 21,649 bp to be highly methylated. A comparison of the PcMYB10 promoter methylation level between the MRB and MRB-G forms indicated a correlation between hypermethylation and the green-skin phenotype. An Agrobacterium tumefaciens infiltration assay was conducted on young MRB fruits by using a plasmid constructed to silence endogenous PcMYB10 via DNA methylation. The infiltrated fruits showed blocked anthocyanin biosynthesis, higher methylation of the PcMYB10 promoter, and lower expression of PcMYB10 and PcUFGT. We suggest that the methylation level of PcMYB10 is associated with the formation of the greenskinned sport in the MRB pear. The potential mechanism behind the regulation of anthocyanin biosynthesis is discussed.

A DEMETER-like DNA demethylase governs tomato fruit ripening

“…In addition, engineering DNA demethylation in tomato fruits would be an innovative and novel strategy for the improvement of traits of agronomical relevance in a species with little genetic diversity (30). Finally, the recent demonstration that hypermethylation of a Myb promoter blocks anthocyanin accumulation during pear and apple ripening (31,32) supports the notion of a more general role for demethylation in fruits. However, whether this mechanism occurs similarly during the ripening of all fleshy fruit species now requires further investigation.…”

The Jasmonate-Activated Transcription Factor MdMYC2 Regulates ETHYLENE RESPONSE FACTOR and Ethylene Biosynthetic Genes to Promote Ethylene Biosynthesis during Apple Fruit Ripening

“…Due to the long juvenile period of transgenic apple plants, we used a transient expression assay to silence MdMYC2 expression in apple fruit by Agrobacterium infiltration, a widely used method for studying gene function (Jia et al, 2011;Wang et al, 2013;Han et al, 2015;Li et al, 2016). MdMYC2-suppressed apple fruit (MdMYC2-AN) showed slower ripening than control fruits after MeJA treatment ( Figure 9C), as well as significantly lower MdACS1 and MdACO1 expression ( Figures 9D and 9E) and ethylene production ( Figure 9G).…”

Knockdown of Carotenoid Cleavage Dioxygenase 4 (CCD4) via Virus-Induced Gene Silencing Confers Yellow Coloration in Peach Fruit: Evaluation of Gene Function Related to Fruit Traits

“…Li et al (2012) succeeded in silencing an apple CONSTITUTIVE PHOTOMORPHOGENIC 1 in apple peel, resulting in the hyper-accumulation of anthocyanin. Furthermore, Wang et al (2013) triggered the transcriptional gene silencing with TRV-based virus vectors in the young pear fruit skin. More recently, one report on TRV-based gene silencing in peach fruits was published in which silencing of NAC by VIGS led to the bleaching of the red-fleshed peach (Zhou et al 2015).…”