Zongda Xu

Prunus mume (mei), which was domesticated in China more than 3,000 years ago as ornamental plant and fruit, is one of the first genomes among Prunus subfamilies of Rosaceae been sequenced. Here, we assemble a 280M genome by combining 101-fold next-generation sequencing and optical mapping data. We further anchor 83.9% of scaffolds to eight chromosomes with genetic map constructed by restriction-site-associated DNA sequencing. Combining P. mume genome with available data, we succeed in reconstructing nine ancestral chromosomes of Rosaceae family, as well as depicting chromosome fusion, fission and duplication history in three major subfamilies. We sequence the transcriptome of various tissues and perform genome-wide analysis to reveal the characteristics of P. mume, including its regulation of early blooming in endodormancy, immune response against bacterial infection and biosynthesis of flower scent. The P. mume genome sequence adds to our understanding of Rosaceae evolution and provides important data for improvement of fruit trees. The Prunus mume was domesticated in China over 3,000 years ago and is an important ornamental plant and fruit. Here Qixiang Zhang et al.obtain the first assembly of its genome with a combination of next-generation sequencing, whole-genome mapping and restriction-site-associated DNA.

Flower color is a charming phenotype with very important ornamental and commercial values. Anthocyanins play a critical role in determining flower color pattern formation, and their biosynthesis is typically regulated by R2R3-MYB transcription factors (TFs). Paeonia suffruticosa is a famous ornamental plant with colorful flowers. However, little is known about the R2R3-MYB TFs that regulate anthocyanin accumulation in P. suffruticosa. In the present study, two R2R3-MYB TFs, namely, PsMYB114L and PsMYB12L, were isolated from the petals of P. suffruticosa ‘Shima Nishiki’ and functionally characterized. Sequence analysis suggested that PsMYB114L contained a bHLH-interaction motif, whereas PsMYB12L contained two flavonol-specific motifs (SG7 and SG7-2). Subsequently, the in vivo function of PsMYB114L and PsMYB12L was investigated by their heterologous expression in Arabidopsis thaliana and apple calli. In transgenic Arabidopsis plants, overexpression of PsMYB114L and of PsMYB12L caused a significantly higher accumulation of anthocyanins, resulting in purple-red leaves. Transgenic apple calli overexpressing PsMYB114L and PsMYB12L also significantly enhanced the anthocyanins content and resulted in a change in the callus color to red. Meanwhile, gene expression analysis in A. thaliana and apple calli suggested that the expression levels of the flavonol synthase (MdFLS) and anthocyanidin reductase (MdANR) genes were significantly downregulated and the dihydroflavonol 4-reductase (AtDFR) and anthocyanin synthase (AtANS) genes were significantly upregulated in transgenic lines of PsMYB114L. Moreover, the expression level of the FLS gene (MdFLS) was significantly downregulated and the DFR (AtDFR/MdDFR) and ANS (AtANS/MdANS) genes were all significantly upregulated in transgenic lines plants of PsMYB12L. These results indicate that PsMYB114L and PsMYB12L both enhance anthocyanin accumulation by specifically regulating the expression of some anthocyanin biosynthesis-related genes in different plant species. Together, these results provide a valuable resource with which to further study the regulatory mechanism of anthocyanin biosynthesis in P. suffruticosa and for the breeding of tree peony cultivars with novel and charming flower colors.