Abstract
The red to blue hue of plant organs is caused due to anthocyanins, which are water-soluble flavonoid pigments. The accumulation of these pigments is regulated by a complex of R2R3-MYB transcription factors (TFs), basic-helix-loop-helix (bHLH), and WD-repeat (WDR) proteins (MBW complex). In Rosaceae species, R2R3-MYBs, particularly MYB10 genes, are responsible for part of the natural variation in anthocyanin colors. Japanese plum cultivars, which are hybrids of Prunus salicina, have high variability in the color hue and pattern, going from yellow-green to red and purple-blue, probably as a result of the interspecific hybridization origin of the crop. Because of such variability, Japanese plum can be considered as an excellent model to study the color determination in Rosaceae fruit tree species. Here, we cloned and characterized the alleles of the PsMYB10 genes in the linkage group LG3 region where quantitative trait loci (QTLs) for the organ color have been mapped to other Prunus species. Allele segregation in biparental populations as well as in a panel of varieties, combined with the whole-genome sequence of two varieties with contrasting fruit color, allowed the organization of the MYB10 alleles into haplotypes. With the help of this strategy, alleles were assigned to genes and at least three copies of PsMYB10.1 were identified in some varieties. In total, we observed six haplotypes, which were able to characterize 91.36% of the cultivars. In addition, two alleles of PsMYB10.1 were found to be highly associated with anthocyanin and anthocyanin-less skin. Their expression during the fruit development confirms their role in the fruit skin coloration. Here, we provide a highly efficient molecular marker for the early selection of colored or non-colored fruits in Japanese plum breeding programs.
Highlights
Anthocyanins are water-soluble flavonoid pigments that confer the purple-blue hue to plant organs
Biosynthetic genes of anthocyanins are mostly transcriptionally activated by a complex consisting of R2R3-MYB transcription factors (TFs), basic-helixloop-helix, and WD-repeat (WDR) proteins (MBW complex), that induces the expression of several genes in the anthocyanin biosynthesis pathway by binding directly to their promoters (Koes et al, 2005; Gonzalez et al, 2008)
To amplify and isolate PsMYB10 allelic bands, we used the PCR primers designed in the conserved regions of PpMYB10.1, PpMYB10.2, and PpMYB10.3
Summary
Anthocyanins are water-soluble flavonoid pigments that confer the purple-blue hue to plant organs. Biosynthetic genes of anthocyanins are mostly transcriptionally activated by a complex consisting of R2R3-MYB transcription factors (TFs), basic-helixloop-helix (bHLH), and WD-repeat (WDR) proteins (MBW complex), that induces the expression of several genes in the anthocyanin biosynthesis pathway by binding directly to their promoters (Koes et al, 2005; Gonzalez et al, 2008). MYB TFs can act as a negative regulator of anthocyanin levels by repressing the expression of anthocyanin genes, possibly by recruiting MBW complexes (Albert et al, 2009; Zhou et al, 2019) or by retaining the ability to form an MBW complex and target DNA motifs when the MYB alleles are truncated (Paz-Ares et al, 1990; Gonzalez et al, 2008; Velten et al, 2010)
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