Three R2R3-MYB transcription factors regulate distinct floral pigmentation patterning in Phalaenopsis spp.

Wen-Huei Chen,Wen-Chieh Tsai,Chia-Chi Hsu,You-Yi Chen,Hong-Hwa Chen

doi:10.1104/pp.114.254599

Wen-Huei Chen, Wen-Chieh Tsai + Show 3 more

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https://doi.org/10.1104/pp.114.254599

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Journal: Plant physiology	Publication Date: Mar 4, 2015
Citations: 145	License type: CC BY 4.0

Affiliation: National Cheng Kung University

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.

Highlights

Orchidaceae are well known for their fascinating floral morphologic features, specialized pollination, and distinctive ecological strategies
To study the MYB transcription factors that regulate anthocyanin biosynthesis in Phalaenopsis spp., we identified 16 R2R3-MYB transcription factors (PeMYB1–PeMYB16), including 14 PeMYBs isolated from OrchidBase (Fu et al, 2011; Tsai et al, 2013) and 2 PeMYBs amplified from P. equestris with degenerated primers
Phylogenetic analysis showed PeMYB2, PeMYB11, and PeMYB12 in the same clade as Zea mays C1 (ZmC1), which controls the pigmentation of seeds or kernels (Paz-Ares et al, 1987; Lepiniec et al, 2006), and the same large cluster with dicot anthocyanin-promoting MYBs, including Petunia hybrida Anthocyanin2 (PhAN2) and Antirrhinum majus VENOSA (AmVENOSA), AmROSEA1 (AmROS1), and AmROS2 (Fig. 1)

Summary

Introduction

Orchidaceae are well known for their fascinating floral morphologic features, specialized pollination, and distinctive ecological strategies. (Schwinn et al, 2006; Albert et al, 2011; Davies et al, 2012) Irregular pigmentation patterning, such as color flecks and sectors, was studied in morning glory (Pharbitis purpurea) and other plants and found to be linked to the activated transposon insertion in anthocyanin biosynthetic genes (Inagaki et al, 1994; Iida et al, 1999; Itoh et al, 2002). Other patterns, such as in Petunia spp. The genetic control of petal spots has not been well studied and may differ among species

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