Methylation of MdMYB1 locus mediated by RdDM pathway regulates anthocyanin biosynthesis in apple

Abstract

SummaryMethylation at the MdMYB1 promoter in apple sports has been reported as a regulator of the anthocyanin pathway, but little is known about how the locus is recognized by the methylation machinery to regulate anthocyanin accumulation. In this study, we analysed three differently coloured ‘Fuji’ apples and found that differences in the transcript levels of MdMYB1, which encodes a key regulator of anthocyanin biosynthesis, control the anthocyanin content (and therefore colour) in fruit skin. The CHH methylation levels in the MR3 region (−1246 to −780) of the MdMYB1 promoter were found to be negatively correlated with MdMYB1 expression. Thus, they were ideal materials to study DNA methylation in apple sports. The protein of RNA‐directed DNA methylation (RdDM) pathway responsible for CHH methylation, MdAGO4, was found to interact with the MdMYB1 promoter. MdAGO4s can interact with MdRDM1 and MdDRM2s to form an effector complex, fulfilling CHH methylation. When MdAGO4s and MdDRM2s were overexpressed in apple calli and Arabidopsis mutants, those proteins increase the CHH methylation of AGO4‐binding sites. In electrophoretic mobility shift assays, MdAGO4s were found to specifically bind to sequence containing ATATCAGA. Knockdown of MdNRPE1 did not affect the binding of MdAGO4s to the c3 region of the MdMYB1 promoter in 35S::AGO4 calli. Taken together, our data show that the MdMYB1 locus is methylated through binding of MdAGO4s to the MdMYB1 promoter to regulate anthocyanin biosynthesis by the RdDM pathway.

The assessment of epigenetic diversity, differentiation, and structure in the ‘Fuji’ mutation line implicates roles of epigenetic modification in the occurrence of different mutant groups as well as spontaneous mutants

“…Extensive epigenetic research has been carried out in many plant species, whereas study on the fruit crops is still in progress. So far, the available reports mainly consist of several popular fruit crops such as apple [39][40][41][42][43][44][45][46][47][48], orange [49][50], banana [51], pear [52][53], strawberry [54], and grape [55][56]. Epigenetic studies in bud mutations are just in the initial stages since limited literature is available [40-41, 45-47, 52-53].…”

“…Epigenetic studies in bud mutations are just in the initial stages since limited literature is available [40-41, 45-47, 52-53]. In 'Fuji' apple bud mutation occurrence, epigenetic mechanisms mediated by DNA methylation begun only last year [46][47][48], and all of them were done from the perspective of local DNA methylation. Few studies were performed on global DNA methylation in bud variation with a large sample size even on fruit crops.…”

Integrated metabolic profiling and transcriptome analysis of pigment accumulation in diverse petal tissues in the lily cultivar ‘Vivian’

“…Finally, these genes were grouped with the MYB that activate anthocyanin biosynthesis in other plants, such as AtMYB90, AtMYB75 and AtMYB114 in Arabidopsis thaliana [23], MdMYB1 and MdMBY10 in malus [18,42] and CmMYB6 in chrysanthemum [37]. The differences in transcript levels of MdMYB1, which encoded a key regulator of anthocyanin biosynthesis, controlled the anthocyanin content and color in fruit skin [43]. Overexpression of MdMYB10 in apple generated a strong phenotype, with highly pigmented plants [42].…”

Integrated Metabolic Profiling and Transcriptome Analysis of Pigment Accumulation in Diverse Petal Tissues in the Lily Cultivar 'Vivian'

“…6A), and were closely related to other published anthocyanin-related MYBs, which were promoting pigmentation [1,[26][27][28][29][30][31][32]. For example, the differences in transcript levels of MdMYB1, which encoded a key regulator of anthocyanin biosynthesis, controled the anthocyanin content and color in fruit skin [33].…”