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Molecular Biology: Open Access

Tsai and Sawa, Mol Biol 2018, 7:3
DOI: 10.4172/2168-9547.1000217

ISSN: 2168-9547

Short communication

Open AccessTools to Develop Genetic Model Plants in the Orchidaceae Family
Allen Yi-Lun Tsai and Shinichiro Sawa*
Graduate School of Science & Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto , Japan

Introduction
The Orchidaceae family is estimated to contain about 28,000 species
and over 100,000 hybrids, making it one of the largest taxonomic
groups among flowering plants [1]. The variations in flower colours,
floral organ morphology and scents make orchids highly sought-afterin ornamental horticulture. In addition, orchids are found in nearly
all regions of the world with diverse adaptations, making them aninvaluable resource to study plant evolution and speciation.
Despite orchids’ great economic values and potential in basic
research, currently there are no model plants from the Orchidaceae
family. Unlike the model plant Arabidopsis (Arabidopsis thaliana), theorchid genomes are often large, heterogeneous and complex, making
genetic analyses difficult [2]. Currently transformation techniques havebeen developed for several orchid species [3-5], and Virus-Induced
Gene Silencing (VIGS) has been used to examine loss-of-function
phenotypes [6]. The wind orchid (Neofinetia falcate) is also being
advocated as a model plant for its short stature, small genome and large
mutant collection [7]. Nevertheless, many barriers still prevent orchidsfrom becoming accessible for genetic analyses. Here we summarize twofindings that may help increase the utility of orchids as a genetic modelorganism.
Firstly, orchid transposons may be a useful tool in mutation
mapping. Currently there are no efficient mutagenesis methods fororchids, and the existing mutants are largely isolated and maintainedby hobbyists [7]. Transposon may be able to quickly and methodicallyisolate orchid mutants. Undesirable phenotypic defects can often
appear in cell culture clones during commercial breeding, likely due torandom transposon excision and re-insertion events. A Phalaenopsis
mutant with the floral column partially transformed into petals has
previously been identified and characterized [8]. This floral organconversion resembles the Arabidopsis agamous (ag) mutant, suggesting
this mutant is likely affected in a C class floral organ identity gene [9,10].
Homologues of floral identity genes have been identified in Phalaenopsis,suggesting orchids may utilize floral development mechanism similar
to Arabidopsis [11,12]. Furthermore, wild type-like revertants wereisolated from the progenies of this Phalaenopsis mutant, indicating
the mutation is likely caused by a transposon insertion event, and thephenotype reversed when the transposon is excised [8]. Currently thesequence and identity of this transposon remains unknown, but if thistransposon can be identified it may help to develop Phalaenopsis as agenetic model plant. Snapdragon (Antirrhinum majus) is a successfulmodel plant partially due to its genome contains transposons withknown sequences. This allows the establishment of transposon tagging
lines to easily identify genes affected by transposon insertion [13]. In
addition, the function of the gene in question can easily be tested byisolating revertants resulted from the excision of the transposon.
A second challenge in establishing orchid as a model plant is its
long generation time. Ornamental orchids typically takes two to three
years to propagate one generation, making standard genetic analyses
unfeasibly long in orchids. In vitro flowering system has been developedfor Dendrobium to accelerate flowering, although its culturing conditions
are heavily species-dependent [14]. Recently an Artificial Cultivation
System (ACS) was developed to propagate two obligate mycoheterotrophic
species, Gastrodia pubilabiata and G. confuse [15]. The ACS set-up consists
a cedar log as growth medium, along with humus and cedar cones toMol Biol, an open access journal
ISSN: 2168-9547

promote fungal growth contained within a plastic box [15]. Interestingly,
G. pubilabiata was not only viable in the ACS, but was able to set seeds up
to three times a year, compare to in the natural habitat where it may take atleast one year to set seed [15]. These results suggest that orchid generation
time can potentially be shortened under artificial conditions, such that thetimeframes of genetic analyses become feasible.
In summary, advancements in the Orchidaceae family researchhighlight the orchids’ potential to be used as a genetic tool for basic
research. One direction is to utilize orchid transposon as a mutation
mapping tool. Phenotypic instability is a significant problem in theorchid breeding industry. However if these mutants are indeed causedby transposon insertions, then these mutant populations can be a useful
resource to identify novel genes in development. Another advancement
is to shorten the orchid generation time. Using the ACS, Gastrodia
species can be propagated faster compared to under natural conditions,and currently the Gastrodia inbred line can be maintained up to theF3 generation. In conjunction with the current established molecular
genetic techniques and genome annotation efforts, it is conceivable in
the near future that genetic analyses in the Orchidaceae family becomecommon practices
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*Corresponding author: Sawa S, Professor of Science & Technology , Graduate
School of Science & Technology, Kumamoto University Kurokami 2-39-1,
Kumamoto , Japan, Tel: 096-342-3439; E-mail: sawa@kumamoto-u.ac.jp
Received July 10, 2018; Accepted July 23, 2018; Published July 30, 2018
Citation: Tsai AY, Sawa S (2018) Tools to Develop Genetic Model Plants in theOrchidaceae Family. Mol Biol 7: 217. doi: 10.4172/2168-9547.1000217
Copyright: © 2018 Tsai AY, et al. This is an open-access article distributed under
the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author andsource are credited.

Volume 7 • Issue 3 • 1000217

Citation: Tsai AY, Sawa S (2018) Tools to Develop Genetic Model Plants in the Orchidaceae Family. Mol Biol 7: 217. doi: 10.4172/2168-9547.1000217

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Mol Biol, an open access journal
ISSN: 2168-9547

Volume 7 • Issue 3 • 1000217