WUSCHEL-related Homeobox Research Articles

Microhair on the adaxial leaf surface of salt secreting halophytic Oryza coarctata Roxb. show distinct morphotypes: Isolation for molecular and functional analysis

Halophytic Oryza coarctata is a good model system to examine mechanisms of salinity tolerance in rice. O. coarctata leaves show the presence of microhairs in adaxial leaf surface furrows that secrete salt under salinity. However, detailed molecular and physiological studies of O. coarctata microhairs are limited due to their relative inaccessibility. This work presents a detailed characterization of O. coarctata leaf features. O. coarctata has two types of microhairs on the adaxial leaf surface: longer microhairs (three morphotypes) lining epidermal furrow walls and shorter microhairs (reported first time) arising from bulliform cells. Microhair morphotypes include (i) finger-like, tubular structures, (ii) tubular hairs with bilobed and flattened heads and (iii) bi-or trifurcated hairs. The unicellular nature of microhairs was confirmed by propidium iodide (PI) staining. An efficient method for the isolation and enrichment of O. coarctata microhairs is presented (yield averaging ˜2 × 105/g leaf tissue). The robustness of the microhair isolation procedure was confirmed by subsequent viability staining (PI), total RNA isolation and RT-PCR amplification of O. coarctata trichome-specific WUSCHEL-related homeobox 3B (OcWox3B) and transporter gene-specific cDNA sequences. The present microhair isolation work from O. coarctata paves the way for examining genes involved in ion secretion in this halophytic wild rice model.

SERK Receptor-like Kinases Control Division Patterns of Vascular Precursors and Ground Tissue Stem Cells during Embryo Development in Arabidopsis

During embryo development, the vascular precursors and ground tissue stem cells divide to renew themselves and produce the vascular tissue, endodermal cells, and cortical cells. However, the molecular mechanisms regulating division of these stem cells have remained largely elusive. In this study, we show that loss of function of SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) genes results in aberrant embryo development. Fewer cortical, endodermal, and vascular cells are generated in the embryos of serk1 serk2 bak1 triple mutants. WUSCHEL-RELATED HOMEOBOX 5 (WOX5) is ectopically expressed in vascular cells of serk1 serk2 bak1 embryos. The first transverse division of vascular precursors in mid-globular embryos and second asymmetric division of ground tissue stem cells in early-heart embryos are abnormally altered to a longitudinal division. The embryo defects can be partially rescued by constitutively activated mitogen-activated protein kinase (MAPK) kinase kinase YODA (YDA) and MAPK kinase MKK5. Taken together, our results reveal that SERK-mediated signals regulate division patterns of vascular precursors and ground tissue stem cells, likely via the YDA-MKK4/5 cascade, during embryo development.

Genome-wide identification and analysis of the WUSCHEL-related homeobox (WOX) gene family in allotetraploid Brassica napus reveals changes in WOX genes during polyploidization

BackgroundWUSCHEL-related homeobox (WOX) genes encoding plant-specific homeobox (HB) transcription factors play important roles in the growth and development of plants. To date, WOX genes has been identified and analyzed in many polyploids (such as cotton and tobacco), but the evolutionary analysis of them during polyploidization is rare. With the completion of genome sequencing, allotetraploid Brassica napus and its diploid progenitors (B. rapa and B. oleracea) are a good system for studying this question.ResultsIn this study, 52, 25 and 29 WOX genes were identified in allotetraploid B. napus (2n = 4x = 38, AnCn), the An genome donor B. rapa (2n = 2x = 20, Ar) and the Cn genome donor B. oleracea (2n = 2x = 18, Co), respectively. All identified WOX genes in B. napus and its diploid progenitors were divided into three clades, and these genes were selected to perform gene structure and chromosome location analysis. The results showed that at least 70 and 67% of WOX genes maintained the same gene structure and relative position on chromosomes, respectively, indicating that WOX genes in B. napus were highly conserved at the DNA level during polyploidization. In addition, the analysis of duplicated genes and transposable elements (TEs) near WOX genes showed that whole-genome triplication (WGT) events, segmental duplication and abundant TEs played important roles in the expansion of the WOX gene family in B. napus. Moreover, the analysis of the expression profiles of WOX gene pairs with evolutionary relationships suggested that the WOX gene family may have changed at the transcriptional regulation level during polyploidization.ConclusionsThe results of this study increased our understanding of the WOX genes in B. napus and its diploid progenitors, providing a rich resource for further study of WOX genes in these species. In addition, the changes in WOX genes during the process of polyploidization were discussed from the aspects of gene number, gene structure, gene relative location and gene expression, which provides a reference for future polyploidization analysis.

Genome-wide identification of WOX genes and their expression patterns under different hormone and abiotic stress treatments in tea plant (Camellia sinensis)

Plant-specific WUSCHEL-related homeobox (WOX) transcription factors regulate plant developmental processes, especially those involved in embryogenesis. However, studies on WOX family genes in tea plants do not exist. In this study, a total of eighteen CsWOX members were identified in the tea plant genome and divided into three clades based on the phylogenetic results; they included ancient, intermediate and modern clades, which reflected the evolutionary history of WOX families. Furthermore, ancient clade members had more gene structural variations than other clade members and had unique conserved motifs. The expression profiles of eight tissues showed that six CsWOX genes were highly expressed in at least four tissues, while other genes were expressed at a very low level or not expressed. Moreover, numerous cold-, drought-, ethylene-, methyl jasmonate (MeJA)-, abscisic acid (ABA)-, and gibberellic acid (GA)-responsive cis-elements were observed in the CsWOX promoter regions, and we subsequently investigated their expression patterns under these treatments. Notably, the ancient clade members may play more active roles than members of the other clades in environmental adaptation in tea plants. Our work provides precise information on CsWOX family genes that will benefit the further understanding of their functional roles in tea plants.

Characterization of JsWOX1 and JsWOX4 during Callus and Root Induction in the Shrub Species Jasminum sambac.

Plant regeneration in vitro and the underlying molecular regulatory network are of great interest to developmental biology, and have potential applications in agriculture and biotechnology. Cell growth and re-differentiation during de novo organogenesis require the activation and reprogramming of stem cells within the stem cell niche of the tissues. The WUSCHEL-related homeobox (WOX) factors play important roles in the maintenance and regulation of plant stem cells and are involved in many developmental processes. However, in woody species such as the Jasminum sambac, little is known about the involvement of WOX genes in de novo organogenesis. Here we show that two WOXs, JsWOX4 and JsWOX1, are implicated in callus proliferation and root regeneration, respectively. The expression of both, together with another member JsWOX13, are upregulated during later stage of callus formation. The JsWOX4 is associated with callus proliferation, or cell division during the redifferentiation. The overexpression of this gene results in up-regulation of JsWOX13 and another homeobox gene. The JsWOX1 plays a role in root primordium initiation, as its overexpression leads to more rooty calli and more roots per callus. JsWOX1 also possibly acts upstream of JsWOX4 and JsWOX13 transcriptionally. Our results provide further evidence regarding the functions of WOX genes in organogenesis in a woody plant.

Transcriptomic analysis reveals the regulatory module of apple (Malus \xd7 domestica) floral transition in response to 6-BA

BackgroundInsufficient production of flower buds is an intractable problem in ‘Fuji’ apple orchards. Although cytokinin (CK) promotes flower bud formation in apple trees, little is known about the mechanisms regulating this phenomenon.ResultsIn the present study, high-throughput RNA sequencing (RNA-Seq) of ‘Nagafu No. 2’ buds was conducted to characterize the transcriptional response to 6-BA treatment during key period of floral transition. A weighted gene co-expression network analysis (WGCNA) of the differentially expressed genes identified hormone signal transduction pathways, totaling 84 genes were highly correlated with the expression pattern of flowering-time genes. The up-regulation of CK signal components and a gibberellin (GA) signal repressor were found to contribute to the promotion of floral transition. In relative comparison to non-treated buds, a series of sugar metabolism- and signal- related genes were associated with relatively high levels of sucrose, fructose, and glucose during floral induction in the 6-BA treated buds. Several transcription factors (i.e. SPLs, SOC1, FD, and COL) that are involved in GA, aging, and photoperiod-regulated flowering pathways were also upregulated by the 6-BA treatment. In addition, potential transcription factors integrating CK signaling to trigger floral induction in apple were also assessed; including PHYTO-CHROME-INTERACTING FACTOR (PIF1,3), WUSCHEL-related homeobox (WOX3,13), and CK response regulators (ARR2).ConclusionsThe present study provides insight into the response of flowering and development-related pathways and transcription factors to 6-BA during the period of floral transition in apple. It extends our knowledge of the fundamental mechanisms associated with CK-regulated floral transition in apple trees.

Control of de novo root regeneration efficiency by developmental status of Arabidopsis leaf explants

De novo root regeneration (DNRR) has wide applications in agriculture such as those related to cutting technology. Detached Arabidopsis thaliana leaf explants can regenerate adventitious roots without added hormones. The regenerative ability is highly dependent on the developmental status of the leaf. An immature leaf has a higher regenerative ability, while a mature leaf is difficult to regenerate. Using RNA-Seq analysis, we showed that the expression levels of many genes, including those in the auxin network, changed during leaf maturation. Particularly, the expression levels of many YUCCA (YUC) genes in the auxin biosynthesis pathway are responsive to leaf maturation. Overexpression of YUC1 in the yuc-1D dominant mutant rescued the rooting defects caused by leaf maturation. In addition, YUC4 expression levels were also affected by circadian rhythms. The regenerative ability was reduced in both immature and mature mutant leaf explants from the new wuschel-related homeobox 11-3 (wox11-3) and wox12-3 mutant alleles created by the CRISPR/Cas9 method. Overall, the transcriptome and genetic data, together with the auxin concentration analysis, indicate that the ability to upregulate auxin levels upon detachment may be reduced during leaf maturation. Thus, multiple developmental and environmental signals may converge to control auxin accumulation, which affects the efficiency of the WOX11/12-mediated DNRR from leaf explants.

Identification and characterization of the WUSCHEL-related homeobox (WOX) genes family in Passiflora organensis

In model plants, such as Arabidopsis thaliana, changes in floral morphology, as well as in plant architecture, depend on the behavior of the stem meristem (vegetative, inflorescence and floral), whose control is directly related to the expression of the WUSCHEL (WUS) gene belonging to the WUSCHEL-related homeobox (WOX) gene group. The sequencing of Passiflora organensis genome will allow the identification and analysis of key genes expression in the development of this genus plants. The present work intends to identify and characterize the members of the WOX gene family in Passiflora, with a focus on investigating the role of the WUS gene in P. organensis by analyzing the gene expression by qRT-PCR and in situ hybridization.

Genetic demonstration of the involvement of WUSCHEL-related homeobox (WOX) genes in narrow-petal and narrow-leaf mutations in traditional Japanese azalea cultivars

The spider-type azalea cultivars, Rhododendron kaempferi ‘Kin-kujyaku’ and Rhododendron macrosepalum ‘Seigaiha’, are characterized by extremely narrow leaves and choripetalous flowers with narrow petals. Previous morphological analysis of these cultivars revealed that narrowed organs would be a common mutation in the growth of lateral organs in the transverse plane. In the present study, we focused on the analysis of WUSCHEL-related homeobox (WOX) genes, WOX1 and WOX3, which regulate the laminar width and development of lateral organs. Sequence analysis of the two genes confirmed a fatal mutation in Rk/RmWOX3/SPIDER of ‘Kin-kujyaku’ and ‘Seigaiha’. To demonstrate the role of SPIDER in the spider-type phenotype in azalea, we performed genotyping using DNA markers developed for multiplex PCR that can distinguish between the wild-type and the spider-type allele based on the partial mutated region of RkWOX3/SPIDER in ‘Kin-kujyaku’. The investigation of BC1 population derived from ‘Kin-kujyaku’ confirmed complete co-segregation between spider-type mutation and Rkwox3/spider band pattern of DNA markers. Therefore, we concluded that SPIDER is responsible for the spider-type mutation in azalea.

Peptide signaling molecules CLE5 and CLE6 affect Arabidopsis leaf shape downstream of leaf patterning transcription factors and auxin.

Intercellular signaling mediated by small peptides is critical to coordinate organ formation in animals, but whether extracellular polypeptides play similar roles in plants is unknown. Here we describe a role in Arabidopsis leaf development for two members of the CLAVATA3/ESR‐RELATED peptide family, CLE5 and CLE6, which lie adjacent to each other on chromosome 2. Uniquely among the CLE genes, CLE5 and CLE6 are expressed specifically at the base of developing leaves and floral organs, adjacent to the boundary with the shoot apical meristem. During vegetative development CLE5 and CLE6 transcription is regulated by the leaf patterning transcription factors BLADE‐ON‐PETIOLE1 (BOP1) and ASYMMETRIC LEAVES2 (AS2), as well as by the WUSCHEL‐RELATED HOMEOBOX (WOX) transcription factors WOX1 and PRESSED FLOWER (PRS). Moreover, CLE5 and CLE6 transcript levels are differentially regulated in various genetic backgrounds by the phytohormone auxin. Analysis of loss‐of‐function mutations generated by genome engineering reveals that CLE5 and CLE6 independently and together have subtle effects on rosette leaf shape. Our study indicates that the CLE5 and CLE6 peptides function downstream of leaf patterning factors and phytohormones to modulate the final leaf morphology.

Global Analysis of WOX Transcription Factor Gene Family in Brassica napus Reveals Their Stress- and Hormone-Responsive Patterns.

The plant-specific WUSCHEL-related homeobox (WOX) transcription factor gene family is important for plant growth and development but little studied in oil crops. We identified and characterized 58 putative WOX genes in Brassica napus (BnWOXs), which were divided into three major clades and nine subclades based on the gene structure and conserved motifs. Collinearity analysis revealed that most BnWOXs were the products of allopolyploidization and segmental duplication events. Gene structure analysis indicated that introns/exons and protein motifs were conserved in each subclade and RNA sequencing revealed that BnWOXs had narrow expression profiles in major tissues and/or organs across different developmental stages. The expression pattern of each clade was highly conserved and similar to that of the sister and orthologous pairs from Brassica rapa and Brassica oleracea. Quantitative real-time polymerase chain reaction showed that members of the WOX4 subclade were induced in seedling roots by abiotic and hormone stresses, indicating their contribution to root development and abiotic stress responses. 463 proteins were predicted to interact with BnWOXs, including peptides regulating stem cell homeostasis in meristems. This study provides insights into the evolution and expression of the WOX gene family in B. napus and will be useful in future gene function research.

PtWOX11 acts as master regulator conducting the expression of key transcription factors to induce de novo shoot organogenesis in poplar.

WUSCHEL-RELATED HOMEOBOX 11 establishes the acquisition of pluripotency during callus formation and accomplishes de novo shoot formation by regulating key transcription factors in poplar. De novo shoot regeneration is a prerequisite for propagation and genetic engineering of elite cultivars in forestry. However, the regulatory mechanism of de novo organogenesis is poorly understood in tree species. We previously showed that WUSCHEL (WUS)-RELATED HOMEOBOX 11 (PtWOX11) of the hybrid poplar clone 84K (Populus alba × P. glandulosa) promotes de novo root formation. In this study, we found that PtWOX11 also regulates de novo shoot regeneration in poplar. The overexpression of PtWOX11 enhanced de novo shoot formation, whereas overexpression of PtWOX11 fused with the transcriptional repressor domain (PtWOX11-SRDX) or reduced expression of PtWOX11 inhibited this process, indicating that PtWOX11 promotes de novo shoot organogenesis. Although PtWOX11 promotes callus formation, overexpression of PtWOX11 and PtWOX11-SRDX also produced increased and decreased numbers of de novo shoots per unit weight, respectively, implying that PtWOX11 promotes de novo shoot organogenesis partially by regulating the intrinsic mechanism of shoot development. RNA-seq and qPCR analysis further revealed that PtWOX11 activates the expression of PLETHORA1 (PtPLT1) and PtPLT2, whose Arabidopsis paralogs establish the acquisition of pluripotency, during incubation on callus-inducing medium. Moreover, PtWOX11 activates the expression of shoot-promoting factors and meristem regulators such as CUP-SHAPED COTYLEDON2 (PtCUC2), PtCUC3, WUS and SHOOT MERISTEMLESS to fulfill shoot regeneration during incubation on shoot-inducing medium. These results suggest that PtWOX11 acts as a central regulator of the expression of key genes to cause de novo shoot formation. Our studies further provide a possible means to genetically engineer economically important tree species for their micropropagation.

Root stem cell niche organizer specification by molecular convergence of PLETHORA and SCARECROW transcription factor modules.

Continuous formation of somatic tissues in plants requires functional stem cell niches where undifferentiated cells are maintained. In Arabidopsis thaliana, PLETHORA (PLT) and SCARECROW (SCR) genes are outputs of apical-basal and radial patterning systems, and both are required for root stem cell specification and maintenance. The WUSCHEL-RELATED HOMEOBOX 5 (WOX5) gene is specifically expressed in and required for functions of a small group of root stem cell organizer cells, also called the quiescent center (QC). PLT and SCR are required for QC function, and their expression overlaps in the QC; however, how they specify the organizer has remained unknown. We show that PLT and SCR genetically and physically interact with plant-specific teosinte-branched cycloidea PCNA (TCP) transcription factors to specify the stem cell niche during embryogenesis and maintain organizer cells post-embryonically. PLT-TCP-SCR complexes converge on PLT-binding sites in the WOX5 promoter to induce expression.

Cytokinin signalling regulates organ identity via the AHK4 receptor in Arabidopsis.

Mutual interactions of the phytohormones, cytokinins and auxin determine root or shoot identity during postembryonic de novo organogenesis in plants. However, our understanding of the role of hormonal metabolism and perception during early stages of cell fate reprogramming is still elusive. Here we show that auxin activates root formation, whereas cytokinins mediate early loss of the root identity, primordia disorganisation and initiation of shoot development. Exogenous and endogenous cytokinins influence the initiation of newly formed organs, as well as the pace of organ development. The process of de novo shoot apical meristem establishment is accompanied by accumulation of endogenous cytokinins, differential regulation of genes for individual cytokinin receptors, strong activation of AHK4-mediated signalling and induction of the shoot-specific homeodomain regulator WUSCHEL. The last is associated with upregulation of isopentenyladenine-type cytokinins, revealing higher shoot-forming potential when compared with trans-zeatin. Moreover, AHK4-controlled cytokinin signalling negatively regulates the root stem cell organiser WUSCHEL RELATED HOMEOBOX5 in the root quiescent centre. We propose an important role for endogenous cytokinin biosynthesis and AHK4-mediated cytokinin signalling in the control of de novo-induced organ identity.

Role of CLE41 Peptide in the Development of Root Storage Parenchyma in Species of the Genus Raphanus L.

CLE peptides (CLAVATA3/ENDOSPERM SURROUNDING REGION) are signal molecules or plant peptide hormones that play an important role in regulation of development of various meristems governing the expression of WOX (WUSCHEL-RELATED HOMEOBOX) genes. In particular, CLE peptides belonging to a small TDIF (Tracheary Element Differentiation Inhibitory Factor) group are responsible for the operation of gene WOX4 controlling the development of cambium and the conducting system. We looked into the role of CLE41 peptide from the TDIF group in the development of storage root in two species of the genus Raphanus: cultivated radish (Raphanus sativus var. radicula Pers.) that is a popular root crop with a storage root and its ancestor wild radish (Raphanus raphanistrum L.) where storage parenchyma of the root is poorly developed. It was shown that overexpression of gene RsCLE41 and plant treatment with exogenous peptide CLE41 influenced the development of cambium and xylem in the roots of R. sativus and R. raphanistrum and affected expression of the genes from different groups. One could say that peptide CLE41 activates expression of the genes whose homologues in arabidopsis play a key role in the maintenance of cambium (RsWOX4, RsWOX14, RsHAM4, and RsCYCD3). In the storage root of radish, peptide CLE41 activates proliferation of cambium cells reducing the amount of one of the xylem’s elements (lignified parenchyma). The obtained results point to an important role of CLE41 in the development of storage root in radish.

Genome-wide identification and characterization of WUSCHEL-related homeobox (WOX) genes in Salix suchowensis

Members of the WUSCHEL-related homeobox (WOX) transcription factor family are essential for determining cell fate and regulating diverse developmental processes in plants. Many WOX genes have been systematically investigated in woody plants such as Populus trichocarpa, but not in Salix suchowensis. Whole-genome sequence data for S. suchowensis is now available for comprehensive study of WOX genes in S. suchowensis. We thus surveyed the genome of S. suchowensis and demonstrated active expression of 15 WOX genes. In a phylogenetic analysis of WOX genes, the 15 SsWOX genes clustered among the modern/WUS, intermediate and ancient clades similar to the WOX genes of Arabidopsis thaliana. Based on the conserved intron/exon structure, SsWOX genes in the same subgroup had similar conserved exon–intron structures and motif domains. Furthermore, among several SsWOX subgroups, WUS (Wuschel)-box and EAR (the ERF-associated amphiphilic repression)-like motifs were conserved. Expression profiles of WOX genes in roots, stems and leaves indicate that SsWOX genes have various conserved roles in the tissues. Comparative analysis of the expression patterns in Salix suchowensis with that of Arabidopsis suggests that different shoot regeneration abilities are controlled by different WOX genes in plants. The analysis provide an overview of differentially expressed SsWOX genes during shoot regeneration, but also contribute to understanding the evolution of WOX genes in Salicaceae and the interrelations of WOX genes and other transcription factors, providing targets for further study.

The 6xABRE Synthetic Promoter Enables the Spatiotemporal Analysis of ABA-Mediated Transcriptional Regulation.

The water stress-associated hormone abscisic acid (ABA) acts through a well-defined signal transduction cascade to mediate downstream transcriptional events important for acclimation to stress. Although ABA signaling is known to function in specific tissues to regulate root growth, little is understood regarding the spatial pattern of ABA-mediated transcriptional regulation. Here, we describe the construction and evaluation of an ABSCISIC ACID RESPONSIVE ELEMENT (ABRE)-based synthetic promoter reporter that reveals the transcriptional response of tissues to different levels of exogenous ABA and stresses. Genome-scale yeast one-hybrid screens complemented these approaches and revealed how promoter sequence and architecture affect the recruitment of diverse transcription factors (TFs) to the ABRE. Our analysis also revealed ABA-independent activity of the ABRE-reporter under nonstress conditions, with expression being enriched at the quiescent center and stem cell niche. We show that the WUSCHEL RELATED HOMEOBOX5 and NAC DOMAIN PROTEIN13 TFs regulate QC/SCN expression of the ABRE reporter, which highlights the convergence of developmental and DNA-damage signaling pathways onto this cis-element in the absence of water stress. This work establishes a tool to study the spatial pattern of ABA-mediated transcriptional regulation and a repertoire of TF-ABRE interactions that contribute to the developmental and environmental control of gene expression in roots.

Identification of Polycomb Repressive Complex1, Trithorax group genes and their simultaneous expression with WUSCHEL, WUSCHEL-related Homeobox5 and SHOOT MERISTEMLESS during the induction phase of somatic embryogenesis in Medicago truncatula Gaertn.

The Polycomb Repressive Complex1 (LHP1, RING1, BMI1, EMF1, VRN1) and Trithorax group (ATX2, ATX3.1, ATX3.2, ATX5-like) genes, were for the first time identified in the genome of Medicago truncatula. Their expression, along with that of the earlier-identified MtWUS, MtWOX5 and MtSTM, was investigated during the induction phase (IP). During the 21-day-long IP, all the genes mentioned, except for MtSTM, were expressed in non-embryogenic (M9) and embryogenic (M9–10a) genotype of M. truncatula. The lower expression level of all the PRC1 genes in primary explants of the M9–10a line compared to their expression in the M9 line probably triggers processes leading to the formation of embryogenic cells. In addition, the higher—from the second day of the induction phase—expression of the ATX2, ATX3.1 and ATX3.2 genes from the TrxG in cells of the embryogenic line, compared to the expression in the non-embryogenic one, suggests their involvement in acquisition of cell competence for embryogenesis. Among the three tested genes known for their involvement in organization of the meristematic centers in zygotic embryos (MtWUS, MtWOX5, MtSTM), two (MtWUS and MtWOX5) can serve as markers of cell dedifferentiation in leaf explants of both lines. Moreover, MtSTM may mark embryogenic cells, since its expression was registered only in the embryogenic line. The study provides new data regarding involvement of the PRC1 and TrxG genes during prime events of the SE and sheds new light on the involvement of MtWUS, MtWOX5 and MtSTM in the process.

Identification and Characterization of the WOX Family Genes in Five Solanaceae Species Reveal Their Conserved Roles in Peptide Signaling

Members of the plant-specific WOX (WUSCHEL-related homeobox) transcription factor family have been reported to play important roles in peptide signaling that regulates stem cell maintenance and cell fate specification in various developmental processes. Even though remarkable advances have been made in studying WOX genes in Arabidopsis, little is known about this family in Solanaceae species. A total of 45 WOX members from five Solanaceae species were identified, including eight members from Solanum tuberosum, eight from Nicotiana tomentosiformis, 10 from Solanum lycopersicum, 10 from Nicotiana sylvestris and nine from Nicotiana tabacum. The newly identified WOX members were classified into three clades and nine subgroups based on phylogenetic analysis using three different methods. The patterns of exon-intron structure and motif organization of the WOX proteins agreed with the phylogenetic results. Gene duplication events and ongoing evolution were revealed by additional branches on the phylogenetic tree and the presence of a partial WUS-box in some non-WUS clade members. Gene expression with or without CLE (clavata3 (clv3)/embryo surrounding region-related) peptide treatments revealed that tobacco WOX genes showed similar or distinct expression patterns compared with their Arabidopsis homologues, suggesting either functional conservation or divergence. Expression of Nicotiana tabacum WUSCHEL (NtabWUS) in the organizing center could rescue the wus-1 mutant phenotypes in Arabidopsis, implying conserved roles of the Solanaceae WOX proteins in peptide-mediated regulation of plant development.

Identification and characterization of WUSCHEL-related homeobox (WOX) gene family in economically important orchid species Phalaenopsis equestris and Dendrobium catenatum

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.