Peach [Prunus persica L. (Batsch)], planted world widely, is an important fruit tree crop, but also functions as ornamental planting with attractive colors of flowers and leaves. Many researches on red coloration in ornamental trees have focused on genetic basis. However, there are few reports on the molecular mechanism underlying this scientific puzzle in ornamental trees or other deciduous trees.    

Peach leaf color is controlled by a single  gene (Gr), with red allele dominant over green allele, which is mapped on linkage group (LG) 6. A research team led by Prof. HAN Yuepeng from Wuhan Botanical Garden identified a candidate gene in the ‘Gr’ locus by comparing transcriptomes of a red-color leaves cultivar ‘Hongyetao’ (HYT) and a green-color leaves cultivar ‘Mantianhong’ (MTH) and verified its role in anthocyanin biosynthesis by transient transformation in tobacco and peach leaves. 

Transcriptomes of young leaves from cultivar HYT and MTH were sequenced using Illumina RNA-seq technology, yielding 16 and 11 million transcript reads, respectively. Of the 129 genes in the Gr locus, 18 genes were identified to be differentially expressed between red- and green-colored leaves. Of these genes, only one (ppa018744m) encoding a transcription factor homologous to Arabidopsis. AtMYB113 was related to anthocyanin biosynthesis. The gene, designated PpMYB10.4, showed 239.5 times higher level of expression in red-colored leaves than in green-colored leaves.   

The research found that the expression levels of anthocyanin structural genes PpCHS, PpCHI, PpF3H, PpF3’H, PpDFR, and PpLDOX showed higher levels of expression in red-colored leaves than in green-colored leaves. This demonstrated that accumulation of anthocyanin in peach leaf was regulated at the transcriptional level.    

In Agrobacterium-mediated transient expression assay on tobacco leaves, an intense pigmentation was detected at infiltration sites 7 days after transformation with both PpMYB10.4 and PpbHLH3, but not in the control (PpbHLH3 only). In particle bombardment-mediated transient expression in green-colored young leaves of cultivar MTH, the leaves turned red 2 days after transformation with PpMYB10.4, but the leaves transformed with empty vector were still green in color. 

This study suggests that the ancient duplicated MYB transcription factor PpMYB10.4 is the candidate gene in the Gr locus, and it can induce the anthocyanin biosynthesis and accumulation by activating the structure genes in the pathway. 

Results were published in BMC Plant Biology online entitled “Transcriptome analysis and transient transformation suggest an ancient duplicated MYB transcription factor as a candidate gene for leaf red coloration in peach”. This work was supported by National 863 program of China and the National Natural Science Foundation of China.