A De Novo Floral Transcriptome Reveals Clues into Phalaenopsis Orchid Flower Development

Abstract

Phalaenopsis has a zygomorphic floral structure, including three outer tepals, two lateral inner tepals and a highly modified inner median tepal called labellum or lip; however, the regulation of its organ development remains unelucidated. We generated RNA-seq reads with the Illumina platform for floral organs of the Phalaenopsis wild-type and peloric mutant with a lip-like petal. A total of 43,552 contigs were obtained after de novo assembly. We used differentially expressed gene profiling to compare the transcriptional changes in floral organs for both the wild-type and peloric mutant. Pair-wise comparison of sepals, petals and labellum between peloric mutant and its wild-type revealed 1,838, 758 and 1,147 contigs, respectively, with significant differential expression. PhAGL6a (CUFF.17763), PhAGL6b (CUFF.17763.1), PhMADS1 (CUFF.36625.1), PhMADS4 (CUFF.25909) and PhMADS5 (CUFF.39479.1) were significantly upregulated in the lip-like petal of the peloric mutant. We used real-time PCR analysis of lip-like petals, lip-like sepals and the big lip of peloric mutants to confirm the five genes’ expression patterns. PhAGL6a, PhAGL6b and PhMADS4 were strongly expressed in the labellum and significantly upregulated in lip-like petals and lip-like sepals of peloric-mutant flowers. In addition, PhAGL6b was significantly downregulated in the labellum of the big lip mutant, with no change in expression of PhAGL6a. We provide a comprehensive transcript profile and functional analysis of Phalaenopsis floral organs. PhAGL6a PhAGL6b, and PhMADS4 might play crucial roles in the development of the labellum in Phalaenopsis. Our study provides new insights into how the orchid labellum differs and why the petal or sepal converts to a labellum in Phalaenopsis floral mutants.

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

“…Recently, the roles of B-and E-class MADS-box genes were revealed for orchid tepal development (Tsai et al, 2004;Tsai et al, 2005;Lu et al, 2007;Hsieh et al, 2013a;Su et al, 2013b;Pan et al, 2014;Hsu et al, 2015b;Huang et al, 2015;Huang et al, 2016). We have shown that knock-down expression of Eclass PeSEP1-4 genes reduced the expression of PeERF1.…”

The genome and transcriptome of the Phalaenopsis yield insights into floral organ development and flowering regulation

“…were significantly altered in both genotypes (Huang et al 2015). Transcription factors (TFs) play a role in floral organ development.…”

“…Of the 3,309 putative TF genes identified in the Phalaenopsis genome showed differences in expression between the wild-type and peloric mutant plants (Dataset S11). Notably, the PhAGL6b gene was upregulated in the peloric lateral inner tepals (liplike petals) and lip organs (Huang et al 2015). We therefore cloned the full-length sequence of…”

Highly Efficient Proliferation and Regeneration of Protocorm-like Bodies (PLBS) of the Threatened Orchid, Phalaenopsis bellina

“…Phalaenopsis or commonly known as 'Butterfly orchid', is one of the most popular orchids in the trade (Huang et al 2015). The Phalaenopsis genus comprises approximately 66 species that can be divided into five subgenera, namely Proboscidioides, Aphyllae, Parishianae, Polychilos and Phalaenopsis .…”

“…The Phalaenopsis genus comprises approximately 66 species that can be divided into five subgenera, namely Proboscidioides, Aphyllae, Parishianae, Polychilos and Phalaenopsis . These species are widely distributed in the Asia (India, Malaysia and Taiwan), Australia and the larger islands of the Pacific Ocean (Huang et al 2015). The plant is an epiphyte with fleshy, copious and adventitious roots arising from the base and lower nodes of stem.…”