Search

In the present study, we identified and characterized the plant-specific WUSCHEL -related homeobox (WOX ) gene family that plays a major role in the determination of cell fate, early embryonic pattern formation, stem cell maintenance, organogenesis, flower development and somatic embryogenesis. For this purpose, the transcriptomes of four species of Phalaenopsis, namely P. aphrodite, P. modesta, P. bellina and P. lueddemanniana, were analysed, and nine PaWOX, ten PmWOX, eight PbWOX and nine PlWOX transcripts were identified. The duplication event analysis showed the presence of two duplication events in P. lueddemanniana, one each in P. bellina and P. modesta and no duplication event in P. aphrodite. During the evolutionary analysis, all the WOX proteins were clustered with those of Arabidopsis thaliana (AtWOX), Phalaenopsis equestris (PeWOX), Apostasia shenzhenica and Dendrobium catenatum (DcWOX). The expression analysis of the WOX genes suggested their critical role in floral development and in other developmental processes. The secondary and tertiary structural analysis of seven selected WOX proteins was then performed, with each protein representing its respective clade. The results provide a valuable resource for further studies of the molecular mechanisms of floral and vegetative developments in Phalaenopsis species.

Orchid flowers have unique floral organisation which make them indispensable to the floral industry. The MADS-box gene family encodes for transcription factors that are involved mainly in floral or...

Orchids have a huge reservoir of secondary metabolites making these plants of immense therapeutic importance. Their potential as curatives has been realized since times immemorial and are extensively studied for their medicinal properties. Secondary metabolism is under stringent genetic control in plants and several molecular factors are involved in regulating the production of the metabolites. However, due to the complex molecular networks, a complete understanding of the specific molecular cues is lacking. High-throughput omics technologies have the potential to fill up this lacuna. The present study deals with comparative analysis of high-throughput transcript data involving gene identification, functional annotation, and differential expression in more than 30 orchid transcriptome data sets, with a focus to elucidate the role of various factors in alkaloid and flavonoid biosynthesis. Comprehensive analysis of the mevalonate (MVA) pathway, methyl-d-erythritol 4-phosphate (MEP) pathway, and phenylpropanoid pathway provide specific insights to the potential gene targets for drug discovery. It is envisaged that a positive stimulation of these pathways through regulation of pivotal genes and alteration of specific gene expression, could facilitate the production of secondary metabolites and enable efficient tapping of the therapeutic potential of orchids. This further would lay the foundation for developing strategies for genetic and epigenetic improvement of these plants for development of therapeutic products.

Background Phospholipases hydrolyze glycerophospholipids and generate diverse lipid-derived molecules with secondary messenger activity. Out of these, phospholipase C (PLC) specifically cleaves the phospholipids at ester linkages and yields diacylglycerol (DAG) and phosphorylated head groups. PLCs are classified further as phosphatidylinositol-specific PLCs (PI-PLCs) and non-specific PLCs with biased specificity for phosphatidylcholine (NPC/PC-PLC). Results In the present report, we identified and characterized PLC genes in the genomes of three orchids, Phalaenopsis equestris (seven PePLCs), Dendrobium catenatum (eight DcPLCs), and Apostasia shenzhenica (seven AsPLCs). Multiple sequence alignment analysis confirmed the presence of conserved X and Y catalytic domains, calcium/lipid-binding domain (C2 domain) at the C terminal region, and EF-hand at the N-terminal region in PI-PLC proteins and esterase domain in PC-PLC. Systematic phylogenetic analysis established the relationship of the PLC protein sequences and clustered them into two groups (PI-PLC and PC-PLC) along with those of Arabidopsis thaliana and Oryza sativa. Gene architecture studies showed the presence of nine exons in all PI-PLC genes while the number varied from one to five in PC-PLCs. RNA-seq-based spatio-temporal expression profile for PLC genes was generated, which showed that PePC-PLC1, PePC-PLC2A, DcPC-PLC1A, DcPC-PLC1B, DcPC-PLC2, DcPC-PLC1B, and AsPC-PLC1 had significant expression in all reproductive and vegetative tissues. The expression profile is matched to their upstream cis-regulatory promoter elements, which indicates that PLC genes have a role in various growth and development processes and during stress responses. Conclusions The present study unwrapped the opportunity for functional characterization of selected PLC genes in planta for plant improvement.

Orchids are diverse and economically important ornamental plants with mesmerising floral morphology and extended flower longevity. Recent whole genome sequencing of the selected orchids enabled genome-wide characterization of various gene families with economic importance. WUSCHEL-related homeobox (WOX) transcription factors are plant specific homeobox proteins, which participate in multiple developmental activities, especially during embryogenesis, organogenesis and florogenesis. In the present study, a total of 14 WOX genes were identified in Phalaenopsis equestris and 10 from Dendrobium catenatum. The phylogenetic analysis and protein characterization revealed the conserved nature of WOX proteins in both the species. However, PeWOX and DcWOX genes differed in their exon-intron organization. Three gene duplication events were predicted in P. equestris whereas no such event was found in D. catenatum. Majority of WOX genes were tissue specific, while certain genes showed expression in all developmental stages. It was also observed that the expression of WOX genes was comparable among orthologs. The expression pattern matched the cis-regulatory promoter elements predicted in the upstream region. The present study unfurls the potential for functional characterization of selected WOX genes in heterologous system and in planta.

Glutathione peroxidases (GPXs) are redox sensor proteins that maintain a steady-state of H2O2 in plant cells. They exhibit distinct sub-cellular localization and have diverse functionality in response to different stimuli. In this study, a total of 14 TaGPX genes and three splice variants were identified in the genome of Triticum aestivum and evaluated for various physicochemical properties. The TaGPX genes were scattered on the various chromosomes of the A, B, and D sub-genomes and clustered into five homeologous groups based on high sequence homology. The majority of genes were derived from the B sub-genome and localized on chromosome 2. The intron-exon organization, motif and domain architecture, and phylogenetic analyses revealed the conserved nature of TaGPXs. The occurrence of both development-related and stress-responsive cis-acting elements in the promoter region, the differential expression of these genes during various developmental stages, and the modulation of expression in the presence of biotic and abiotic stresses suggested their diverse role in T. aestivum. The majority of TaGPX genes showed higher expression in various leaf developmental stages. However, TaGPX1-A1 was upregulated in the presence of each abiotic stress treatment. A co-expression analysis revealed the interaction of TaGPXs with numerous development and stress-related genes, which indicated their vital role in numerous biological processes. Our study revealed the opportunities for further characterization of individual TaGPX proteins, which might be useful in designing future crop improvement strategies.

Reactive oxygen species (ROS) induce oxidative stress at high concentrations and act as signaling molecules at low concentrations. Superoxide dismutases (SOD) are defence-related proteins, which are involved in detoxifying ROS. SODs have been characterized in various plants, but their comprehensive characterization has not been performed in Triticum aestivum. Herein, a total of 23 TaSOD genes were identified, which were classified into fourteen TaCu-ZnSOD and nine TaFe-MnSOD genes based on their domain organization. These genes were located on various homeologous chromosomes of each A, B and D-subgenome. Higher number of genes on each subgenome than their progenitor genome indicated the role of duplication events during the evolution of TaSODs. The phylogenetic analysis indicated evolutionary conservation in SODs from various plant species. Gene structure in terms of exon/intron organization and intron-phase, and physico-chemical properties like molecular weight and pI was variably conserved in homeologous TaSODs. Most of the Cu-ZnSODs were predicted as cytoplasmic, while Fe-MnSODs were chloroplastic and mitochondrial. Both TaCu-ZnSODs and TaFe-MnSODs were found structurally conserved in terms of various metal binding and active sites, and secondary and tertiary structures as well. They showed putative interaction with each other and other ROS detoxifying enzymes like catalases and peroxidases. Specifically high expression of a few TaSODs in certain tissue developmental stages suggested their precise role in those tissues. TaFe-MnSOD1 group genes were highly expressed during development of grain. Constitutive expression of certain genes indicated their role during all developmental stages. The modulated expression of a few genes during biotic (TaCu-ZnSOD3-A, TaFe-MnSOD2-A) and abiotic stresses (heat; TaCu-ZnSOD3-B, TaFe-MnSOD1-B, drought; TaFe-MnSOD1-A, salt; TaFe-MnSOD2-A) suggested their function in a stress response. The present study provided inclusive characterization of SOD proteins in T. aestivum, which extends the opportunity for future functional characterization of each individual protein.

Somatic embryogenesis receptor kinases (SERKs) play a significant role in morphogenesis, stress/defense and signal transduction. In the present study, we have identified two SERK and 11 SERK-like (SERL) genes in Phalaenopsis equestris, two SERK and 11 SERL genes in Dendrobium catenatum, and one SERK and eight SERL genes in Apostasia shenzhenica genome. Characterization of the SERK proteins revealed the presence of a signal peptide, a leucine zipper, five leucine-rich repeats (LRRs), a serine proline proline (SPP) motif, a transmembrane region, a kinase domain, and a C-terminus. Most of the SERK/SERL proteins were characterized with similar physicochemical properties. The presence of transmembrane region predicted their membranous localization. Tertiary structure prediction of all the five identified SERK proteins had sequence identity with BAK1 protein of Arabidopsis thaliana. Generally, all the SERK/SERL genes shared similar gene architecture and intron phasing. Gene ontology analysis indicated the role of SERKs in receptor and ATP binding, signal transduction, and protein phosphorylation. Phylogenetic analysis revealed the clustering of SERKs and SERLs in distinct clades. Expression of SERKs in reproductive tissues like floral bud, floral stalk, whole flower and pollen was reported to be higher than their expression in vegetative tissues with an exception of PeSERK1 and DcSERK1 which showed higher expression in leaves and roots, respectively. Likewise, a higher expression of AsSERK1 was observed in tubers. However, lower expression of SERLs was observed in majority of tissues studied irrespective of their vegetative or reproductive origin. This work paves way for future studies involving functional characterization of SERK/SERLs and their potential role in embryogenesis/organogenesis as an aid to regeneration and multiplication of endangered orchids.

Orchids constitute one of the largest, diverse, cosmopolitan and highly evolved plant families, the Orchidaceae. Due to their poorly developed reproductive barriers, they are in a constant state of evolutionary flux and active speciation. Epiphytic habit in orchids, expose these plants to light and water stress which in turn encourage modifications and adaptations. The flowers have a complex structure with one of the petal being variously modified into a labellum, which forms the basis of their immense importance as ornamentals. As a result, they are in huge demand in floriculture industry. Additionally, orchids have been significantly reported in ancient therapeutic scriptures. There have been a large number of reports of their curative and restorative role potential. They are considered to be highly habitat specific and show poor propagation in nature owing to their microscopic seeds with undifferentiated embryos and no endosperm, and dependence on a symbiotic association with mycorrhizal fungi for continued germination. They are also considered to be good indicators of environmental degradation. Owing to their immense demand in floriculture industry as well as therapeutics, these plants have been under constant stress from various environmental sources as well as anthropogenic pressures. With the advent of molecular technology, there have been constant efforts to ameliorate the deleterious effects of environment stresses in orchids. The present review deals with the various molecular interventions involved in dealing with these environmental stresses.

A study was conducted on seed morphometry of seven threatened Himalayan orchids (listed in Appendix II of CITES) belonging to three different subfamilies, and exhibiting terrestrial (Arundina graminifolia, Cypripedium cordigerum, Habenaria marginata, Herminium monorchis), mycoheterotrophic (Gastrodia falconeri) or epiphytic (Aerides multiflora, Pholidota articulata) life modes. Seeds were fusiform, filiform or ovoid in shape and their size showed direct correlation with plant habit. They were relatively smaller in epiphytes than their terrestrial or mycoheterotrophic counterparts. Seeds were truncated except in Arundina graminifolia (l/w > 6.0). Scanning electron micrographs revealed that the testa cells were longitudinally oriented, arranged either straight or in a spiral, and their periclinal walls were comparatively irregularly placed in epiphytic species. The wall thickenings were also more pronounced in epiphytes. Embryos were tiny and most of the seed space (even > 90% in Pholidota articula...

Physical seed characteristics of 32 threatened Western Himalayan orchids belonging to 23 genera of 3 subfamilies were studied using light and scanning electron microscopy. The species showed remarkable seed shape variations (fusiform, spathulate, ovoid, filiform) irrespective of their taxonomic position. Epiphytes produced relatively small-sized seeds compared to their terrestrial, lithophytic, or mycoheterotrophic counterparts. Seeds were truncated (length/width < 6.0) in 27 species, and were mostly elongated (length/width = 19.957 ± 1.459) in the orchidoid species Goodyera biflora (Lindl.) Hook.f. The number or size of testa cells was found fairly consistent at the genus level, and their walls were straight, sinuous, or undulate. Periclinal walls possessed vertical or oblique ornamentation in 6 species, which is of taxonomic implication. Embryos were rather tiny and most of the seed space (even >90% in 7 species) was occupied by air. The highest seed to embryo volume ratio was recorded in terrestrial Liparis odorata (Willd.) Lindl. and the lowest in epiphytic Rhynchostylis retusa (L.) Blume, both of which are members of the advanced Epidendroideae. Seed characteristics are important in elucidating taxonomic, phylogenetic, and phytogeographic relationships among different orchid taxa.

Present paper deals with asymbiotic ger-mination potential of immature seeds in Aeridesmultiflora Roxb. for its rapid mass propagation in vitro. Seeds were inoculated on Potato Dex-trose Agar (PDA) medium with and without growth adjuncts (CH, Casein Hydrolysate; P, Pep-tone, YE, Yeast Extract; each 0.1%) and activated charcoal (AC; 0.2%). Seed germination initiated after 1.20±0.42 weeks (wks) on CH supplement-ed medium. The percent germination response showed significant differences in majority of combinations used; it was lowest (48.00±2.16) in basal medium and highest (99.50±0.85) in medi-um supplemented with CH and AC. Protocorm formation started after 4.15±0.48 wks of cultur-ing on CH and AC containing medium. First leaf and first root differentiated after 7.30±0.82 and 14.00±0.67 wks of culturing respectively on me-dium supplemented with P and AC. Seedlings with 3–4 leaves and 2–3 roots were obtained af-ter 18.30±0.67 wks. The medium supplemented with CH and AC proved to be the best for seed germination, protocorm formation and multipli-cation, and that containing P and AC for early leaf and root differentiation, and seedling devel-opment. The seedlings were subjected to hard-ening and 72.56±3.18% of them survived under greenhouse conditions.

Cypripedium cordigerum D. Don is a beautiful species of lady slipper orchids which is endemic to the Himalayan range. Ongoing anthropogenic pressures have jeopardized its populations to such an extent that it has been declared ‘Rare’ in Red Data Book of Indian plants. Since formulation and successful execution of conservation strategies in such rare species highly depend upon information regarding their distribution and habitat ecology, present study was undertaken to document such details of C. cordigerum in Himachal Pradesh. The species was found restricted in distribution to Kullu, Shimla and Sirmaur districts, and inhabited shady moist habitats of temperate and subalpine regions (2130–3550 m). Species density [individual(s)/mm2] was highest (2.09) at Fagu and lowest (0.41) at Churdhar. Slightly acidic to nearly neutral soils (pH 6.34–6.92) with higher contents of organic C, N, P and K were best suited for its growth and development. Deforestation and overgrazing were key factors responsible for shrinkage of its natural populations in the state.

This study was carried out to evaluate the differential responses of 6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA) on regeneration competence of pseudobulb segments of Dendrobium moschatum Sw., an epiphytic orchid of immense ornamental importance. Mitra et al. (1976) media supplemented with different (0.5–2 mgl−1) concentrations of BA and NAA were employed to elucidate their multivariate effects on morphogenetic parameters using response surface methodology. Surface analysis clearly indicated that regeneration response, at both lower and higher concentrations of BA, increased with increase in NAA levels. The proliferative potential of pseudobulb explants was markedly influenced by their position on donor axis; basal segments were better used for inducing multiple proliferative loci. An average of 28.8 plantlets could be harvested on medium supplemented with BA (2mgl−1) and NAA (0.5mgl−1) within 24 weeks. The present protocol can serve as an aid for propagation and conservation of diminishing natural populations of D. moschatu.