De novo sequencing and comparative transcriptome analysis of white petals and red labella in Phalaenopsis for discovery of genes related to flower color and floral differentation

Abstract

Phalaenopsis is one of the world's most popular and important epiphytic monopodial orchids. The extraordinary floral diversity of Phalaenopsis is a reflection of its evolutionary success. As a consequence of this diversity, and of the complexity of flower color development in Phalaenopsis, this species is a valuable research material for developmental biology studies. Nevertheless, research on the molecular mechanisms underlying flower color and floral organ formation in Phalaenopsis is still in the early phases. In this study, we generated large amounts of data from Phalaenopsis flowers by combining Illumina sequencing with differentially expressed gene (DEG) analysis. We obtained 37 723 and 34 020 unigenes from petals and labella, respectively. A total of 2736 DEGs were identified, and the functions of many DEGs were annotated by BLAST-searching against several public databases. We mapped 837 up-regulated DEGs (432 from petals and 405 from labella) to 102 Kyoto Encyclopedia of Genes and Genomes pathways. Almost all pathways were represented in both petals (102 pathways) and labella (99 pathways). DEGs involved in energy metabolism were significantly differentially distributed between labella and petals, and various DEGs related to flower color and floral differentiation were found in the two organs. Interestingly, we also identified genes encoding several key enzymes involved in carotenoid synthesis. These genes were differentially expressed between petals and labella, suggesting that carotenoids may influence Phalaenopsis flower color. We thus conclude that a combination of anthocyanins and/or carotenoids determine flower color formation in Phalaenopsis. These results broaden our understanding of the mechanisms controlling flower color and floral organ differentiation in Phalaenopsis and other orchids. [191][192][193][194][195][196][197][198][199]

Comparative Metabolomic Analysis Reveals Distinct Flavonoid Biosynthesis Regulation for Leaf Color Development of Cymbidium sinense ‘Red Sun’

“…The enzyme activity of DFR decreased at first and then increased, while the activity of ANS increased at first and then decreased, but the coding genes expression level of the two enzymes was significantly down-regulated. DFR from different plants has specific substrates biases for DHK, DHQ and DHM [6,31], and the downstream DFRs and ANSs is necessary for large sum of anthocyanin accumulation in Phalaenopsis [32,33]. These unstable anthocyanins eventually went through the action of UFGT to form stable anthocyanins [34].…”

A putative miR172-targeted CeAPETALA2-like gene is involved in floral patterning regulation of the orchid Cymbidium ensifolium

“…However, owing to lack of knowledge, extensive investigations are required to further understand the floral ABCDE model in orchid, as shown by Wang et al (2011). Moreover, nearly all of the evidence regarding these ABCDE demotic genes has been derived from Phalaenopsis, and studies in other orchid genera are greatly limited (Huang et al, 2012;Yang et al, 2014).…”

A Walk Through the Maze of Secondary Metabolism in Orchids: A Transcriptomic Approach

“…Similarly, upregulated expression of Pa4CL, PaANS, PaF3H, and PaDFR was detected in purple petal cultivar of Phalaenopsis amabilis (Meng et al, 2019). The study on Phalaenopsis did not identify any DEGs related to CHS, ANS, DFR, and flavonoid-3′-hydroxylase (F3′H) in white petals which could be due to either technical limitations or due to absence of anthocyanin pathway (Yang et al, 2014). Similarly, no transcript of flavonoid-3′,5′-hydroxylase (F3′5′H) was identified from the transcriptome of Ophrys even though 61 transcripts of anthocyanins pathway were mined (Sedeek et al, 2013).…”

“…This can be attributed to specific gene expression in tissues at various stages of growth and development and environmental conditions. In Phalaenopsis amabilis, a comparative number of unigenes were reported, 37,723 and 34,020, from petals and labellum, respectively (Yang et al, 2014), indicating that a similar genetic profile can be seen in tissues at comparable physiological stages. In Anoectochilus roxburghii, 186,865 unigenes were reported from root, stem, and leaves (Chen et al, 2020).…”