Constitutive Activation of an Anthocyanin Regulatory Gene <i>PcMYB10</i>.<i>6</i> Is Related to Red Coloration in Purple-Foliage Plum

<div><p>Cherry plum is a popular ornamental tree worldwide and most cultivars are selected for purple foliage. Here, we report the investigation of molecular mechanism underlying red pigmentation in purple-leaf plum ‘Ziyeli’ (<i>Prunus cerasifera</i> Ehrhar f. atropurpurea (Jacq.) Rehd.), which shows red color pigmentation in fruit (flesh and skin) and foliage. Six anthocyanin-activating MYB genes, designated <i>PcMYB10</i>.<i>1</i> to <i>PcMYB10</i>.<i>6</i>, were isolated based on RNA-Seq data from leaves of cv. Ziyeli. Of these <i>PcMYB10</i> genes, five (<i>PcMYB10</i>.<i>1</i> through <i>PcMYB10</i>.<i>5</i>) show distinct spatial and temporal expression patterns, while the <i>PcMYB10</i>.<i>6</i> gene is highly expressed in all the purple-coloured organs of cv. Ziyeli. Constitutive activation of <i>PcMYB10</i>.<i>6</i> is closely related to red pigmentation in the leaf, fruit (flesh and skin), and sepal. However, the <i>PcMYB10</i>.<i>6</i> activation cannot induce red pigmentation in the petal of cv. Ziyeli during late stages of flower development due to due to a lack of expression of <i>PcUFGT</i>. The inhibition of red pigmentation in the petal of cherry plum could be attributed to the high-level expression of <i>PcANR</i> that directs anthocyanidin flux to proanthocyanidin biosynthesis. In addition, <i>PcMYB10</i>.<i>2</i> is highly expressed in fruit and sepal, but its expression cannot induce red pigmentation. This suggests the <i>PcMYB10</i> gene family in cherry plum may have diverged in function and <i>PcMYB10</i>.<i>2</i> plays little role in the regulation of red pigmentation. Our study provides for the first time an example of constitutive activation of an anthocyanin-activating <i>MYB</i> gene in <i>Prunus</i> although its underlying mechanism remains unclear.</p></div

qRT-PCR analysis of the expression profiles of anthocyanin structural genes (A) and <i>PcMYB10</i> genes (B) in petals of cv.

<p>Ziyeli and Aoben.</p

qRT-PCR analysis of the expression profiles of anthocyanin structural genes (A) and <i>PcMYB10</i> genes (B) in leaves of cv.

<p>Ziyeli and Aoben.</p

A Multi-Population Consensus Genetic Map Reveals Inconsistent Marker Order among Maps Likely Attributed to Structural Variations in the Apple Genome

<div><p>Genetic maps serve as frameworks for determining the genetic architecture of quantitative traits, assessing structure of a genome, as well as aid in pursuing association mapping and comparative genetic studies. In this study, a dense genetic map was constructed using a high-throughput 1,536 EST-derived SNP GoldenGate genotyping platform and a global consensus map established by combining the new genetic map with four existing reliable genetic maps of apple. The consensus map identified markers with both major and minor conflicts in positioning across all five maps. These major inconsistencies among marker positions were attributed either to structural variations within the apple genome, or among mapping populations, or genotyping technical errors. These also highlighted problems in assembly and anchorage of the reference draft apple genome sequence in regions with known segmental duplications. Markers common across all five apple genetic maps resulted in successful positioning of 2875 markers, consisting of 2033 SNPs and 843 SSRs as well as other specific markers, on the global consensus map. These markers were distributed across all 17 linkage groups, with an average of 169±33 marker per linkage group and with an average distance of 0.70±0.14 cM between markers. The total length of the consensus map was 1991.38 cM with an average length of 117.14±24.43 cM per linkage group. A total of 569 SNPs were mapped onto the genetic map, consisting of 140 recombinant individuals, from our recently developed apple Oligonucleotide pool assays (OPA). The new functional SNPs, along with the dense consensus genetic map, will be useful for high resolution QTL mapping of important traits in apple and for pursuing comparative genetic studies in Rosaceae.</p> </div

Pigmentation phenotype in flowers (A), leaves (B), and fruits (C) of two cherry plum cultivars Ziyeli and Aoben.

<p>FW1, flower buds at pink stage; FW2, flower buds at the bloom stage; FW3, flowers at full bloom. DAFB, days after full bloom.</p

Features of the new genetic map of apple for Co-op 16×Co-op 17 constructed using SNP OPA designed by [6] and together with markers from [19].

<p>The number of markers, average interval (cM), maximum interval (cM) per linkage group and length (cM) of each linkage group are shown.</p

qRT-PCR analysis of the expression profiles of anthocyanin structural genes (A) and <i>PcMYB10</i> genes (B) in sepals of cv.

<p>Ziyeli and Aoben.</p

Markers with conflicting positions across different studies identified and removed by MergeMap [14] during the construction of a consensus map for apple.

<p>Conflicts in marker position in these markers could be attributed to technical errors and the segmental duplication in apple genome. The name of marker, map, linkage group according to marker sequence similarity based on apple genome sequence, number of maps that carry this marker, and multi-locus status is given in the table. Similarity is reported if <i>e</i>-values of the marker sequence are more than 0.01.</p><p>Note:</p>*<p>Sequence similarity of SNP and SSR forward and reverse primers against the apple draft genome sequence. Number in parenthesis represents the linkage group(s). Multiple regions on the same linkage group showing similarity (<i>e</i>-value >0.01) are shown by the number outside the parenthesis. The abbreviation ‘un’ stands for unanchored sequence.</p>**<p>Number within parenthesis is linkage group while outside is how many maps have this marker. The abbreviation ‘un’ stands for un-anchored sequence.</p>***<p>Represent multiple loci amplified by one marker; number in parenthesis is the linkage group, while number outside of the parenthesis is the number of maps wherein this marker is present.</p

Phylogenetic tree derived from nucleotide acid sequence of anthocyanin-activating <i>MYB</i> genes in plants.

<p>Anthocyanin-activating <i>MYB</i> genes isolated in this study are highlighted in grey color. The GeneBank Accession numbers of these <i>MYB</i> genes are as follows: <i>Arabidopsis thaliana AtMYB75</i> (AF062908), <i>AtMYB90</i> (AF062915), <i>AtMYB113</i> (NM_105308), and <i>AtMYB114</i> (AY008379); <i>Malus × domestica MdMYB1</i> (AB744001) and <i>MdMYB10</i> (EU518249); <i>Prunus persica PpMYB10</i>.<i>1</i> (ppa026640m), <i>PpMYB10</i>.<i>2</i> (ppa016711m), <i>PpMYB10</i>.<i>3</i> (ppa020385m), <i>PpMYB10</i>.<i>4</i> (ppa018744m), <i>PpMYB10</i>.<i>5</i> (ppa024617m), and <i>PpMYB10</i>.<i>6</i> (ppa022808m); <i>Vitis vinifera VvMYBA1</i> (FJ687552) and <i>VvMYBA2</i> (DQ886419).</p

qRT-PCR analysis of the expression profiles of anthocyanin structural genes (A) and <i>PcMYB10</i> genes (B) in fruit skin of cv.

<p>Ziyeli and Aoben.</p