Three R2R3-MYB Transcription Factors Regulate Distinct Floral Pigmentation Patterning in Phalaenopsis spp.  

Abstract

Orchidaceae are well known for their fascinating floral morphologic features, specialized pollination, and distinctive ecological strategies. With their long-lasting flowers of various colors and pigmentation patterning, Phalaenopsis spp. have become important ornamental plants worldwide. In this study, we identified three R2R3-MYB transcription factors PeMYB2, PeMYB11, and PeMYB12. Their expression profiles were concomitant with red color formation in Phalaenopsis spp. flowers. Transient assay of overexpression of three PeMYBs verified that PeMYB2 resulted in anthocyanin accumulation, and these PeMYBs could activate the expression of three downstream structural genes Phalaenopsis spp. Flavanone 3-hydroxylase5, Phalaenopsis spp. Dihydroflavonol 4-reductase1, and Phalaenopsis spp. Anthocyanidin synthase3. In addition, these three PeMYBs participated in the distinct pigmentation patterning in a single flower, which was revealed by virus-induced gene silencing. In the sepals/petals, silencing of PeMYB2, PeMYB11, and PeMYB12 resulted in the loss of the full-red pigmentation, red spots, and venation patterns, respectively. Moreover, different pigmentation patterning was regulated by PeMYBs in the sepals/petals and lip. PeMYB11 was responsive to the red spots in the callus of the lip, and PeMYB12 participated in the full pigmentation in the central lobe of the lip. The differential pigmentation patterning was validated by RNA in situ hybridization. Additional assessment was performed in six Phalaenopsis spp. cultivars with different color patterns. The combined expression of these three PeMYBs in different ratios leads to a wealth of complicated floral pigmentation patterning in Phalaenopsis spp.

Ectopic Expression of the Grape Hyacinth (Muscari armeniacum) R2R3-MYB Transcription Factor Gene, MaAN2, Induces Anthocyanin Accumulation in Tobacco

“…However, the anthocyanin-related MYBs in Orchidaceae are categorized into the C1 subgroup in Poaceae that includes Z. mays C1 and Oryza sativa MYB (CAA75509) (Chiou and Yeh, 2008; Ma et al, 2009; Hsu et al, 2015; Li et al, 2017). Schwinn et al (2016) speculated that the distinct clades of AN2 and C1 subgroup in the R2R3-MYB family might occur within the monocot Asparagales in the evolution process of Allioideae and Orchidaceae.…”

PeERF1, a SHINE-Like Transcription Factor, Is Involved in Nanoridge Development on Lip Epidermis of Phalaenopsis Flowers

“…We randomly selected 6 to 8 positive clones for sequencing. For gene expression analysis, quantitative real-time RT-PCR (qRT-PCR) was performed in triplicate and repeated independently three times as previously described (Hsu et al, 2015a). Primers for all the PCR and qRT-PCR experiments are in Supplementary Table S1.…”

The CYCLOIDEA–RADIALIS module regulates petal shape and pigmentation, leading to bilateral corolla symmetry in Torenia fournieri (Linderniaceae)

“…R2R3-MYB transcription factors have been recruited in the control of various pigmentation patterns (Schwinn et al, 2006;Albert et al, 2011;Shang et al, 2011;Martins et al, 2013Martins et al, , 2016Nishijima et al, 2013;Hsu et al, 2015). In A. majus, pigmentation is often associated with veins and is determined by an R2R3-MYB factor encoded by Venosa (Schwinn et al, 2006;Shang et al, 2011).…”

“…In Phalaenopsis spp. (Orchidaceae), three R2R3-MYBs -PeMYB2, PeMYB11, and PeMYB12are responsible for background pigmentation, petal spots, and venation patterns, respectively (Hsu et al, 2015). In Clarkia (Myrtales), different alleles of an R2R3-MYB transcription factor gene, CgMYB1, are expressed in different regions of the petal and are responsible for the variations in spot pigmentation (Martins et al, 2016).…”