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In the present study, we report identification and characterization of the plant-specific WUSCHEL-related homeobox (WOX) gene family in Apostasia shenzhenica, a primeval orchid. WOX proteins are DNA-binding WUSCHEL-related homeobox (WOX) encoding transcription factors that play critical role in zygote patterning, embryo development, organogenesis, florigenesis, stress responses etc. Ten putative AsWOX genes were predicted in the A. shenzhenica genome and were characterized by the presence of DNA-binding helix-loop-helix-turn-helix motif. AsWOX proteins were grouped into three clades, ancient, intermediate and WUS on the basis of sequence homology with Arabidopsis thaliana (AtWOX), Oryza sativa (OsWOX), Phalaenopsis equestris (PeWOX) and Dendrobium catenatum (DcWOX) and their phylogenetic relationship was established. Gene structure analysis revealed that three AsWOX genes had two introns, six genes had a single intron, and one gene was intron-less. Expression profiling in a variety of tissue (tubers, seeds and pollens) was analysed in light of the presence of specific cis-regulatory elements in the promoter region and their role in various developmental processes was discussed. Three dimensional structures were predicted for three selected AsWOX proteins representing the three clades. The present study provides insights to the role of AsWOX gene family in various vital developmental processes, establishes phylogenetic relationships with related plant species and provides a platform for functional validation of specific AsWOX genes.

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Vanilla planifolia is an economically important orchid, which is being commercially exploited by the food industry for the highly valued secondary metabolite vanillin. WUSCHEL-related homeobox (WOX) gene family encodes for WUSCHEL-related homeobox (WOX) transcription factors that participate in embryogenesis, organogenesis and florigenesis and in diverse plant developmental processes as well. In the present study, we analysed V. planifolia transcriptome and identified 6 WOX (VpWOX) transcripts, that encode putative WOX (VpWOX) transcription factor proteins. Domain analysis was done which indicates the presence of helix-loop-helix-turn-helix which is identifying feature of WOX gene family proteins. We executed phylogenetic clustering for the VpWOX proteins with their counterpart from the model plant Arabidopsis thaliana (AtWOX) and other closely related orchid species, Phalaenopsis equestris (PeWOX), Dendrobium catenatum (DcWOX) and Apostasia shenzhenica (AsWOX) and established their clade specific grouping. Spatio-temporal expression profile for VpWOX genes was analysed for different plant developmental stages which shows that VpWOX13 is expressing uniformly in all the developmental stages whereas, other genes have tissue specific expression. Based on gene expression patterns, we selected four VpWOX proteins and carried out secondary and tertiary structural analysis which indicates the presence of alpha helix and beta turn in the protein structure. The present study provides basic understanding of the functioning of WOX gene family in V. planifolia and paves the path for functional characterization of selected VpWOX genes in planta and in heterologous system in future for commercial utilization.

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.