Floral Organ Development Research Articles

The overall regulatory network and contributions of ABC(D)E model genes in yellowhorn flower development.

Single flowers and double flowers, exhibiting distinct flower morphologies, developmental process and regulatory networks, have garnered significant attention recently. In yellowhorn (Xanthoceras sorbifolium), the cause of double flower variation has been elucidated, yet the differences in regulatory networks between single and double flowers remain unexplored. Here, we investigated transcriptional changes underlying flower development among yellowhorn single- and double-flowered-trees. Transcriptome analysis and weighted gene co-expression network analysis (WGCNA) were applied to identify key genes and reveal the characteristics of single and double flower traits. The involvement of development-specific and flower-type-specific DEGs related to hormone signaling, metabolism, growth and development was identified, and ABC(D)E model genes were found to be closely associated with floral organ development. Overexpression of yellowhorn ABC(D)E model genes in Arabidopsis demonstrated their roles in floral organ development, and the interactions between different pairs of genes were also validated by yeast two-hybrid (Y2H) experiments. Therefore we elucidated differences between yellowhorn single and double flower development, highlighting the roles of yellowhorn ABC(D)E model genes in controlling flower structures, which not only enriches the understanding of yellowhorn flower researches, but also provides insights for studying flower development in other woody species.

Comprehensive genome-wide characterization of the MIKC-type MADS-box family members and the dynamic expression profiling throughout the development of floral buds in Populus tomentosa

Poplar is a major silvicultural tree species for industrial production, with versatile applications in construction, furniture, pulp and biofuel. The phenotypic appearance of male or female floral buds in poplar trees, exhibits a strikingly similar morphology at corresponding developmental stages. However, there are significant differences in internal anatomical structures. The MIKC-type MADS-box transcription factor family plays an indispensable role in regulating the development of floral organs and increasing vegetative biomass, and it is also of great significance in elucidation of the aforementioned morphological differences. This study systematically analyzed the MIKC-type MADS-box transcription factor family in Populus tomentosa. A total of 100 MIKC-type MADS-box genes were identified, which were divided into 14 subfamilies. We examined the physicochemical properties, gene structure, conserved motifs, chromosome distribution, collinearity, promoter cis-acting elements, gene expression profiles, and protein-protein interaction network of these 100 MIKC-type MADS-box members. Excitingly, four clusters of PtMADS members exhibited a high level of abundant expression in the initial and mature floral buds of both male and female, suggesting critical significance in tuning the morphogenesis and development of floral organs, as well as in the modulation of reproductive fitness. The protein-protein interaction network diagram corroborated these findings, substantiating the speculated roles of these genes. Our findings lay a foundational framework for future functional explorations and potential applications of MIKC-type MADS-box genes in this industry tree species.

Integrated Analysis of microRNAs and Transcription Factor Targets in Floral Transition of Pleioblastus pygmaeus.

Bamboo plants have erratic flowering habits with a long vegetative growth and an uncertain flowering cycle. The process of floral transition has always been one of the hot and intriguing topics in bamboo developmental biology. As master modulators of gene expression at the post-transcriptional level, miRNAs play a crucial role in regulating reproductive growth, especially in floral transition of flowering plants. Pleioblastus pygmaeus is a kind of excellent ground cover ornamental bamboo species. In this study, we performed miRNA expression profiling of the shoot buds and flower buds from the bamboo species, to investigate flowering-related miRNAs in bamboo plants. A total of 179 mature miRNAs were identified from P. pygmaeus, including 120 known miRNAs and 59 novel miRNAs, of which 96 (61 known miRNAs and 35 novel miRNAs) were differentially expressed in the shoots at different growth stages. Based on target gene (TG) prediction, a total of 2099 transcription factors (TFs) were annotated to be TGs of the 96 differentially expressed miRNAs (DEMs), corresponding to 839 recordings of DEM-TF pairs. In addition, we identified 23 known DEMs involved in flowering and six known miRNAs related to floral organ development based on previous reports. Among these, there were 11 significantly differentially expressed miRNAs, with 124 TF targets corresponding to 132 DEM-TF pairs in P. pygmaeus. In particular, we focused on the identification of miR156a-SPL (SQUAMOSA Promoter-Binding protein-Like) modules in the age pathway, which are well-known to regulate the vegetative-to-reproductive phase transition in flowering plants. A total of 36 TF targets of miR156a were identified, among which there were 11 SPLs. The Dual-Luciferase transient expression assay indicated miR156a mediated the repression of the PpSPL targets in P. pygmaeus. The integrated analysis of miRNAs and TGs at genome scale in this study provides insight into the essential roles of individual miRNAs in modulating flowering transition through regulating TF targets in bamboo plants.

Alternative splicing variants of IiSEP3 in Isatis indigotica are involved in floral transition and flower development

The SEPALLATA3 genes regulate several aspects of plant development. This study identified four distinct splicing isoforms of the SEPALLATA3 gene in Isatis indigotica (I. indigotica). IiSEP3-1 and IiSEP3-2 have eight exons and were named as IiSEP3-2/1. However, IiSEP3-3 and IiSEP3-4 with the missing sixth exon were labeled IiSEP3ΔK3. Furthermore, the IiSEP3-1 and IiSEP3-4 amino acids sequences lack the V90. IiSEP3 splicing variants were primarily expressed in floral organs, with petals showing the highest expression. Ectopic expression of IiSEP3-2 or IiSEP3-3 may cause early flowering and reduce the number of sepals, petals, and stamens. The ectopic expression of IiSEP3-2 resulted in cauline leaves and sepals converting to carpelloid structures. In contrast, the four floral whorls prematurely wilted, and the entire flower displayed an abortive state when IiSEP3-3 was expressed ectopically. Silencing the IiSEP3 gene of I. indigotica employing VIGS (tobacco rattle virus-mediated virus-induced gene silencing) technology using the TRV-IiSEP3-2/1 vector delayed flowering time and reduced the number of petals and stamens. Plants silenced with TRV-IiSEP3ΔK3 also exhibited similar phenotypes, including fewer sepals. The transcriptome analysis of silenced plants (TRV-IiSEP3-2/1 treatment group) indicated significant alterations in 1861 genes, with 1035 upregulated and 826 downregulated. TRV-IiSEP3ΔK3 treatment altered the expression of 2063 genes in plants, with 1289 genes upregulated and 774 genes transcription inhibited. Y2H and BIFC experiments revealed that IiSEP3-2 and IiSEP3-3 had distinct interacting proteins. Thus, we can conclude that IiSEP3-2 and IiSEP3-3 interact with different proteins, affecting floral transition and organ development in I. indigotica.

Heatwaves exacerbate pollen limitation through reductions in pollen production and pollen vigour.

Increasingly frequent heat waves threaten the reproduction of flowering plants; compromising the future persistence, adaptive capacity, and dispersal of wild plant populations, and also the yield of fruit-bearing crop plants. Heat damages the development of sensitive floral organs and gametes, which inhibits pollen germination, pollen tube growth, and fertilization. However, the role of heat has not been integrated into the framework of pollen quantity and quality limitation and how heat influences the success of cross and self-pollination. We exposed developing flowers to either controlled temperature (25 °C:20 °C) or extreme heat (35 °C:20 °C) over 72h. We then hand-pollinated them with either crossed or self-derived pollen from the same temperature treatment to determine the direct and interactive effects of simulated heatwaves on pollen tube growth and resulting seed set. We also collected anthers from virgin flowers to measure heat impacts on pollen production. Under cooler control temperatures pollen tube survival of self-derived pollen was approximately 27% lower than that of crossed pollen. Pollen tube survival in heat-treated cross-pollinated and heat-treated self-pollinated flowers were 71% and 77% lower compared to flowers cross-pollinated at control temperatures. These differences in pollen tube survival rate between heat-treated cross-pollinated and heat-treated self-pollinated flowers were insignificant. Furthermore, extreme heat reduced seed set by 87%, regardless of pollen origin, and also reduced pollen production during flower development by approximately 20%. Our results suggest flowers that develop during heatwaves are likely to experience exacerbated pollen quantity and quality limitation driven by changes in pollen production and pollen vigour. Heatwave-induced pollen limitation will likely reduce crop yields in agricultural systems, and depress mating and reproduction in wild plant species, the latter of which may hinder the adaptive capacity of plants to a rapidly changing world.

Deciphering the Role of SVP-Like Genes and Their Key Regulation Networks During Reproductive Cone Development in Pinus tabuliformis.

Reproductive development plays an essential role in the perpetuation of genetic material and environmental adaptation. In angiosperms, the Short Vegetative Phase (SVP) serves as a flowering repressor, influencing the development of floral organs. In this study, heterologous transformation of Arabidopsis thaliana with SVP-like genes (PtSVL1 and PtSVL2) derived from Pinus tabuliformis significantly impacted stamen formation and pollen fertility, without altering flowering time. Gene co-expression networks revealed that SVP-like and SOC1-like genes function as key coregulatory transcription factors during the initial stages of cone development in P. tabuliformis. Interestingly, the regulatory module of SOC1 regulated by SVP in angiosperms is absent in conifers and conifer SVP-like exercises its function in a form that is physically bound to SOC1-like. Furthermore, combining the yeast one-hybrid scanning with co-expression network analysis, revealed that SPLs and TPSs were the principal downstream target genes of PtSVL1. Notably, the PtSPL16 promoter is positively regulated by PtSVL1, and overexpression of PtSPL16 results in delayed flowering in Arabidopsis, suggesting that the PtSVL1-PtSPL16 module plays a crucial role in regulating reproductive development in conifers. Collectively, these findings enhance our understanding of the roles of SVP-like genes in conifers and the key regulatory networks centred on PtSVL1 during reproductive cone development.

Effects of SvAPETALA1-5 gene on floral organ development in Senecio vulgaris.

Asteraceae is a large class of eudicots with complex capitulum, and little is known regarding the molecular regulation mechanism of flower development. APETALA1(AP1) belongs to the MADS-box gene family and plays a key role in plant floral induction and floral organ development. In this study, the bioinformatics and tissue-specific expression of AP1 homologous gene SvAP1-5 in Senecio vulgaris were analyzed. Based on VIGS technology, SvAP1-5 gene silencing plants were created, and SvAP1-5 was overexpressed in Solanum nigrum. The results of bioinformatics analysis showed that SvAP1-5 gene had typical MADS-box and K-box structure, and contains FUL motif and paleoAP1 motif at the C-terminal. SvAP1-5 belongs to the euFUL branch of AP1 gene. qRT-PCR results showed that SvAP1-5 was expressed in bracts, petals and carpels, and was highly expressed in carpels. Compared with the control group, SvAP1-5 gene silencing resulted in irregular petal dehiscence, increased stigma division, and carpel dysplasia. The fruit development of SvAP1-5 overexpressing S.nigrum plants was abnormal, and the hyperplastic tissue similar to fruit appeared. In summary, SvAP1-5 gene may be involved in the development of petals and carpels and plays an important role during the development of S.vulgaris.

Marigold (Tagetes erecta) MADS-Box Genes: A Systematic Analysis and Their Implications for Floral Organ Development

Marigold (Tagetes erecta) has a capitulum with two floret types: sterile ray florets and fertile disc florets. This distinction makes marigold a valuable model for studying floral organ development in Asteraceae, where MADS-box transcription factors play crucial roles. Here, 65 MADS-box genes were identified in the marigold genome, distributed across all 12 chromosomes. These genes were classified into type I (13 genes) and type II (52 genes) according to phylogenetic relationships. The gene structure of type I was simpler than that of type II, with fewer conserved motifs. Type I was further divided into three subclasses, Mα (8 genes), Mβ (2 genes), and Mγ (3 genes), while type II was divided into two groups: MIKCC (50 genes) and MIKC* (2 genes), with MIKCC comprising 13 subfamilies. Many type II MADS-box genes had evolutionarily conserved functions in marigold. Expression analysis of type II genes across different organs revealed organ-specific patterns, identifying 34 genes related to flower organ development. Given the distinct characteristics of the two floret types, four genes were specifically expressed only in the petals of one floret type, while twenty genes were expressed in the stamens of disc florets. These genes might have been related to the formation of different floret types. Our research provided a comprehensive and systematic analysis of the marigold MADS-box genes and laid the foundation for further studies on the roles of MADS-box genes in floral organ development in Asteraceae.

Genome-wide analysis of MADS-box genes and their expression patterns in unisexual flower development in dioecious spinach

Evolution of unisexual flowers involves extreme changes in floral development. Spinach is one of the species to discern the formation and evolution of dioecy. MADS-box gene family is involved in regulation of floral organ identity and development and in many other plant developmental processes. However, there is no systematic analysis of MADS-box family genes in spinach. A comprehensive genome-wide analysis and transcriptome profiling of MADS-box genes were undertaken to understand their involvement in unisexual flower development at different stages in spinach. In total, 54 MADS-box genes found to be unevenly located across 6 chromosomes and can be divided into type I and type II genes. Twenty type I MADS-box genes are subdivided into Mα, Mβ and Mγ subgroups. While thirty-four type II SoMADSs consist of 3 MIKC*, and 31 MIKCC -type genes including sixteen floral homeotic MADS-box genes that are orthologous to the proposed Arabidopsis ABCDE model of floral organ identity determination, were identified in spinach. Gene structure, motif distribution, physiochemical properties, gene duplication and collinearity analyses for these genes are performed in detail. Promoters of both types of SoMADS genes contain mainly MeJA and ABA response elements. Expression profiling indicated that MIKCc genes exhibited more dynamic and intricate expression patterns compared to M-type genes and the majority of type-II genes AP1, SVP, and SOC1 sub-groups showed female flower-biased expression profiles, suggesting their role in carpel development, while PI showed male-biased expression throughout flower developmental stages, suggesting their role in stamen development. These results provide genomic resources and insights into spinach dioecious flower development and expedite spinach improvement.

Molecular Mechanisms of MADS-box Genes in Regulating Floral Organ Development in Rice

As one of the most important food crops in China and worldwide, the morphological development of floral organs in rice is crucial, directly affecting its yield and quality. The MADS-box gene family significantly influences the development of floral organs in rice (Oryza sativa L.). This paper reviews the ABCDE model of floral organ development and provides an overview of recent advancements in research on MADS-box genes that influence the characteristics of floral organs in rice.

HaMADS3, HaMADS7, and HaMADS8 are involved in petal prolongation and floret symmetry establishment in sunflower (Helianthus annuus L.).

The development of floral organs, crucial for the establishment of floral symmetry and morphology in higher plants, is regulated by MADS-box genes. In sunflower, the capitulum is comprised of ray and disc florets with various floral organs. In the sunflower long petal mutant (lpm), the abnormal disc (ray-like) floret possesses prolongated petals and degenerated stamens, resulting in a transformation from zygomorphic to actinomorphic symmetry. In this study, we investigated the effect of MADS-box genes on floral organs, particularly on petals, using WT and lpm plants as materials. Based on our RNA-seq data, 29 MADS-box candidate genes were identified, and their roles on floral organ development, especially in petals, were explored, by analyzing the expression levels in various tissues in WT and lpm plants through RNA-sequencing and qPCR. The results suggested that HaMADS3, HaMADS7, and HaMADS8 could regulate petal development in sunflower. High levels of HaMADS3 that relieved the inhibition of cell proliferation, together with low levels of HaMADS7 and HaMADS8, promoted petal prolongation and maintained the morphology of ray florets. In contrast, low levels of HaMADS3 and high levels of HaMADS7 and HaMADS8 repressed petal extension and maintained the morphology of disc florets. Their coordination may contribute to the differentiation of disc and ray florets in sunflower and maintain the balance between attracting pollinators and producing offspring. Meanwhile, Pearson correlation analysis between petal length and expression levels of MADS-box genes further indicated their involvement in petal prolongation. Additionally, the analysis of cis-acting elements indicated that these three MADS-box genes may regulate petal development and floral symmetry establishment by regulating the expression activity of HaCYC2c. Our findings can provide some new understanding of the molecular regulatory network of petal development and floral morphology formation, as well as the differentiation of disc and ray florets in sunflower.

Genome-wide identification and expression pattern analysis of MIKC-Type MADS-box genes in Chionanthus retusus, an androdioecy plant

BackgroundThe MADS-box gene family is widely distributed in the plant kingdom, and its members typically encoding transcription factors to regulate various aspects of plant growth and development. In particular, the MIKC-type MADS-box genes play a crucial role in the determination of floral organ development and identity recognition. As a type of androdioecy plant, Chionanthus retusus have unique gender differentiation. Manifested as male individuals with only male flowers and female individuals with only bisexual flowers. However, due to the lack of reference genome information, the characteristics of MIKC-type MADS-box genes in C. retusus and its role in gender differentiation of C. retusus remain largely unknown. Therefore, it is necessary to identify and characterize the MADS-box gene family within the genome of the C. retusus.ResultsIn this study, we performed a genome-wide identification and analysis of MIKC-type MADS-box genes in C. retusus (2n = 2x = 46), utilizing the latest reference genome, and studied its expression pattern in individuals of different genders. As a result, we identified a total of 61 MIKC-type MADS-box genes in C. retusus. 61 MIKC-type MADS-box genes can be divided into 12 subfamilies and distributed on 18 chromosomes. Genome collinearity analysis revealed their conservation in evolution, while gene structure, domains and motif analysis indicated their conservation in structure. Finally, based on their expression patterns in floral organs of different sexes, we have identified that CrMADS45 and CrMADS60 may potentially be involved in the gender differentiation of C. retusus.ConclusionsOur studies have provided a general understanding of the conservation and characteristics of the MIKC-type MADS-box genes family in C. retusus. And it has been demonstrated that members of the AG subfamily, CrMADS45 and CrMADS60, may play important roles in the gender differentiation of C. retusus. This provides a reference for future breeding efforts to improve flower types in C. retusus and further investigate the role of MIKC-type MADS-box genes in gender differentiation.

Exploring the diversity of galls on Artemisia indica induced by Rhopalomyia species through morphological and transcriptome analyses.

Plant galls generated by insects have highly organized structures, providing nutrients and shelter to the insects living within them. Most research on the physiological and molecular mechanisms of gall development has focused on single galls. To understand the diversity of gall development, we examined five galls with different morphologies generated by distinct species of Rhopalomyia (gall midge; Diptera: Cecidomyiidae) on a single host plant of Artemisia indica var. maximowiczii (Asteraceae). Vasculature developed de novo within the galls, indicating active transport of nutrients between galls and the host plant. Each gall had a different pattern of vasculature and lignification, probably due to differences in the site of gall generation and the gall midge species. Transcriptome analysis indicated that photosynthetic and cell wall-related genes were down-regulated in leaf and stem galls, respectively, compared with control leaf and stem tissues, whereas genes involved in floral organ development were up-regulated in all types of galls, indicating that transformation from source to sink organs occurs during gall development. Our results help to understand the diversity of galls on a single herbaceous host plant.

Morphological Study on the Differentiation of Flower Buds and the Embryological Stages of Male and Female Floral Organs in Lespedeza davurica (Laxm.) Schindl. cv. JinNong (Fabaceae).

Lespedeza davurica (Laxm.) is a leguminous plant with significant ecological benefits, but its embryonic development mechanism remains unclear. We investigated the flower bud differentiation, megaspore and microspore formation, gametophyte development, and embryo and endosperm development in L. davurica. Our aim was to elucidate the relationship between the external morphology and internal development processes of male and female floral organs during growth, as well as the reproductive factors influencing fruiting. The results indicated that although the pistil develops later than the stamen during flower bud differentiation, both organs mature synchronously before flowering. L. davurica pollen exhibits three germination grooves, a reticulate outer wall, and papillary structures on the anther surface. In vivo pollination experiments revealed abnormal spiral growth of L. davurica pollen tubes within the style and the occurrence of callus plugs, which may reduce the seed setting rate. The anther wall development follows the dicotyledonous type, with tetrads formed through microspore meiosis exhibiting both left-right symmetry and tetrahedral arrangements. L. davurica has a single ovule, and the embryo sac develops in the monosporic polygonum type. After dormancy, the zygote undergoes multiple divisions, progressing through spherical, heart-shaped, and torpedo-shaped embryo stages, culminating in a mature embryo. A mature seed comprises cotyledons, hypocotyl, embryo, radicle, and seed coat. Phylogenetic tree analysis reveals a close genetic relationship between L. davurica and other leguminous plants from the genera Lespedeza and Medicago. This study provides valuable insights into the regulation of flowering and hybrid breeding in leguminous plants and offers a new perspective on the development of floral organs and seed setting rates.

Genome-wide analysis of the MADS-box gene family of sea buckthorn (Hippophae rhamnoides ssp. sinensis) and their potential role in floral organ development

Genome-wide analysis of the MADS-box gene family of sea buckthorn (Hippophae rhamnoides ssp. sinensis) and their potential role in floral organ development

Gene Regulatory Network Controlling Flower Development in Spinach (Spinacia oleracea L.).

Spinach (Spinacia oleracea L.) is a dioecious, diploid, wind-pollinated crop cultivated worldwide. Sex determination plays an important role in spinach breeding. Hence, this study aimed to understand the differences in sexual differentiation and floral organ development of dioecious flowers, as well as the differences in the regulatory mechanisms of floral organ development of dioecious and monoecious flowers. We compared transcriptional-level differences between different genders and identified differentially expressed genes (DEGs) related to spinach floral development, as well as sex-biased genes to investigate the flower development mechanisms in spinach. In this study, 9189 DEGs were identified among the different genders. DEG analysis showed the participation of four main transcription factor families, MIKC_MADS, MYB, NAC, and bHLH, in spinach flower development. In our key findings, abscisic acid (ABA) and gibberellic acid (GA) signal transduction pathways play major roles in male flower development, while auxin regulates both male and female flower development. By constructing a gene regulatory network (GRN) for floral organ development, core transcription factors (TFs) controlling organ initiation and growth were discovered. This analysis of the development of female, male, and monoecious flowers in spinach provides new insights into the molecular mechanisms of floral organ development and sexual differentiation in dioecious and monoecious plants in spinach.

Non-cell-autonomous signaling associated with barley ALOG1 specifies spikelet meristem determinacy

Inflorescence architecture and crop productivity are often tightly coupled in our major cereal crops. However, the underlying genetic mechanisms controlling cereal inflorescence development remain poorly understood. Here, we identified recessive alleles of barley (Hordeum vulgare L.) HvALOG1 (Arabidopsis thaliana LSH1 and Oryza G1) that produce non-canonical extra spikelets and fused glumes abaxially to the central spikelet from the upper-mid portion until the tip of the inflorescence. Notably, we found that HvALOG1 exhibits a boundary-specific expression pattern that specifically excludes reproductive meristems, implying the involvement of previously proposed localized signaling centers for branch regulation. Importantly, during early spikelet formation, non-cell-autonomous signals associated with HvALOG1 expression may specify spikelet meristem determinacy, while boundary formation of floret organs appears to be coordinated in a cell-autonomous manner. Moreover, barley ALOG family members synergistically modulate inflorescence morphology, with HvALOG1 predominantly governing meristem maintenance and floral organ development. We further propose that spatiotemporal redundancies of expressed HvALOG members specifically in the basal inflorescence may be accountable for proper patterning of spikelet formation in mutant plants. Our research offers new perspectives on regulatory signaling roles of ALOG transcription factors during the development of reproductive meristems in cereal inflorescences.

SEPALLATA-driven MADS transcription factor tetramerization is required for inner whorl floral organ development.

MADS transcription factors are master regulators of plant reproduction and flower development. The SEPALLATA (SEP) subfamily of MADS transcription factors is required for the development of floral organs and plays roles in inflorescence architecture and development of the floral meristem. SEPALLATAs act as organizers of MADS complexes, forming both heterodimers and heterotetramers in vitro. To date, the MADS complexes characterized in angiosperm floral organ development contain at least 1 SEPALLATA protein. Whether DNA binding by SEPALLATA-containing dimeric MADS complexes is sufficient for launching floral organ identity programs, however, is not clear as only defects in floral meristem determinacy were observed in tetramerization-impaired SEPALLATA mutant proteins. Here, we used a combination of genome-wide-binding studies, high-resolution structural studies of the SEP3/AGAMOUS (AG) tetramerization domain, structure-based mutagenesis and complementation experiments in Arabidopsis (Arabidopsis thaliana) sep1 sep2 sep3 and sep1 sep2 sep3 ag-4 plants transformed with versions of SEP3 encoding tetramerization mutants. We demonstrate that while SEP3 heterodimers can bind DNA both in vitro and in vivo and recognize the majority of SEP3 wild-type-binding sites genome-wide, tetramerization is required not only for floral meristem determinacy but also for floral organ identity in the second, third, and fourth whorls.

The Evolution of the WUSCHEL-Related Homeobox Gene Family in Dendrobium Species and Its Role in Sex Organ Development in D. chrysotoxum.

The WUSCHEL-related homeobox (WOX) transcription factor plays a vital role in stem cell maintenance and organ morphogenesis, which are essential processes for plant growth and development. Dendrobium chrysotoxum, D. huoshanense, and D. nobile are valued for their ornamental and medicinal properties. However, the specific functions of the WOX gene family in Dendrobium species are not well understood. In our study, a total of 30 WOX genes were present in the genomes of the three Dendrobium species (nine DchWOXs, 11 DhuWOXs, and ten DnoWOXs). These 30 WOXs were clustered into ancient clades, intermediate clades, and WUS/modern clades. All 30 WOXs contained a conserved homeodomain, and the conserved motifs and gene structures were similar among WOXs belonging to the same branch. D. chrysotoxum and D. huoshanense had one pair of fragment duplication genes and one pair of tandem duplication genes, respectively; D. nobile had two pairs of fragment duplication genes. The cis-acting regulatory elements (CREs) in the WOX promoter region were mainly enriched in the light response, stress response, and plant growth and development regulation. The expression pattern and RT-qPCR analysis revealed that the WOXs were involved in regulating the floral organ development of D. chrysotoxum. Among them, the high expression of DchWOX3 suggests that it might be involved in controlling lip development, whereas DchWOX5 might be involved in controlling ovary development. In conclusion, this work lays the groundwork for an in-depth investigation into the functions of WOX genes and their regulatory role in Dendrobium species' floral organ development.

The genetic control of herkogamy.

Herkogamy is the spatial separation of anthers and stigmas within complete flowers, and is a key floral trait that promotes outcrossing in many angiosperms. The degree of separation between pollen-producing anthers and receptive stigmas has been shown to influence rates of self-pollination amongst plants, with a reduction in herkogamy increasing rates of successful selfing in self-compatible species. Self-pollination is becoming a critical issue in horticultural crops grown in environments where biotic pollinators are limited, absent, or difficult to utilise. In these cases, poor pollination results in reduced yield and misshapen fruit. Whilst there is a growing body of work elucidating the genetic basis of floral organ development, the genetic and environmental control points regulating herkogamy are poorly understood. A better understanding of the developmental and regulatory pathways involved in establishing varying degrees of herkogamy is needed to provide insights into the production of flowers more adept at selfing to produce consistent, high-quality fruit. This review presents our current understanding of herkogamy from a genetics and hormonal perspective.