Floral Organ Development Research Articles

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.

Heterotrimeric Gα-subunit regulates flower and fruit development in CLAVATA signaling pathway in cucumber.

Flowers and fruits are the reproductive organs in plants and play essential roles in natural beauty and the human diet. CLAVATA (CLV) signaling has been well characterized as regulating floral organ development by modulating shoot apical meristem (SAM) size; however, the signaling molecules downstream of the CLV pathway remain largely unknown in crops. Here, we found that functional disruption of CsCLV3 peptide and its receptor CsCLV1 both resulted in flowers with extra organs and stumpy fruits in cucumber. A heterotrimeric G protein α-subunit (CsGPA1) was shown to interact with CsCLV1. Csgpa1 mutant plants derived from gene editing displayed significantly increased floral organ numbers and shorter and wider fruits, a phenotype resembling that of Csclv mutants in cucumber. Moreover, the SAM size was enlarged and the longitudinal cell size of fruit was decreased in Csgpa1 mutants. The expression of the classical stem cell regulator WUSCHEL (WUS) was elevated in the SAM, while the expression of the fruit length stimulator CRABS CLAW (CRC) was reduced in the fruit of Csgpa1 mutants. Therefore, the Gα-subunit CsGPA1 protein interacts with CsCLV1 to inhibit floral organ numbers but promote fruit elongation, via repressing CsWUS expression and activating CsCRC transcription in cucumber. Our findings identified a new player in the CLV signaling pathway during flower and fruit development in dicots, increasing the number of target genes for precise manipulation of fruit shape during crop breeding.

Floral Initiation, Organogenesis, and Flowering of Mature Paphiopedilum Clair de Lune ‘Edgard Van Belle’ Award of Merit/American Orchid Society Plants Derived from Divisions

Paphiopedilum Clair de Lune ‘Edgard Van Belle’, an excellent Maudiae-type hybrid that has been propagated by artificial division for a long time. We studied its flower bud initiation, development of floral organs, and flowering habits with a view to providing information for flowering control and efficient commercial production. According to our research, the flower bud initiation phase of this cultivar begins in February every year, and 80% of the plants completed sepal primordium differentiation in March, The flower bud differentiation lasts for 6 to 7 months, until flowering in August. Within 1 to 3 months after flower bud differentiation, all tested plants differentiated lateral buds. After 5 to 6 months, the new, aboveground vegetative shoots reached their maximum growth, with an average plant height of 20 cm, five leaves, and a shoot dry weight of more than 3 g. From February to April of the following year, a new cycle of flower development and vegetative growth began. In addition, this cultivar was notably sensitivity to high ambient temperature during the late phase of flower development, with a flower bud drop rate as high as 33.3% under average day/night temperatures of 29.0/26.5 °C.

Flower development and a functional analysis of related genes in Impatiens uliginosa.

Impatiens uliginosa is a plant of the Impatiens, with peculiar flowers. In this study, we combined morphogenesis and molecular biology to explore its development of flowers. An analysis of basic observational data and paraffin sectioning showed that it took approximately 13 d for the floral organs to differentiate. An analysis of the development of inflorescences and floral organs by scanning electron microscopy showed that the inflorescence of I. uliginosa is a spiral raceme. The floral organs differentiated in the following order: lateral sepals (Ls), posterior sepal (Ps), anterior sepals (As), anterior petal (Ap), lateral petals (Lp), stamens (St) and gynoecium (Gy). I. uliginosa was found to have four sepals, and the connate stamens are caused by the fusion and growth of filament appendages. The results of fluorescence quantification and virus-induced gene silencing showed that I. uliginosa had its own unique model for flower development, and there was functional diversity of IuAP1 and IuDEF. Among them, IuAP1 controls the formation of bract s (Br), regulates the morphogenesis of posterior sepal, controls the anthocyanin precipitation of the anterior petals and the formation of lateral petals. IuDEF regulates the morphogenesis of lateral sepals, the length of development of the spur, and controls the size of yellow flower color plaques of the lateral petals. In this study, the process of flower development and the function of flower development genes of I. uliginosa were preliminarily verified. This study provides basic guidance and new concepts that can be used to study the development of Impatiens flowers.

Comprehensive identification and analysis of DUF640 genes associated with rice growth

Protein domains with conserved amino acid sequences and uncharacterized functions are called domains of unknown function (DUF). The DUF640 gene family plays a crucial role in plant growth, particularly in light regulation, floral organ development, and fruit development. However, there exists a lack of systematic understanding of the evolutionary relationships and functional differentiation of DUF640 within the Oryza genus. In this study, 61 DUF640 genes were identified in the Oryza genus. The expression of DUF640s is induced by multiple hormonal stressors including abscisic acid (ABA), cytokinin (CK), ethylene (ETH), and indole-3-acetic acid (IAA). Specifically, OiDUF640-10 expression significantly increased after ETH treatment. Transgenic experiments showed that overexpressing OiDUF640-10 lines were sensitive to ETH, and seedling length was obstructed. Evolutionary analysis revealed differentiation of the OiDUF640-10 gene in O. sativa ssp. indica and japonica varieties, likely driven by natural selection during the domestication of cultivated rice. These results indicate that OiDUF640-10 plays a vital role in the regulation of rice seedling length.

OfBFT genes play an essential role in the proliferate flower formation of Osmanthus fragrans

Floral organ development is one of the most vital events in flowering plants and is closely related to ornamental properties. The proliferate flower (a new branch or flower occurring in the centre of a flower) in plants is an interesting type, while the specific molecular mechanism remains largely unknown. Osmanthus fragrans 'Tianxiang Taige' has two different flower morphologies: normal flower and proliferate flower. Phenotypic observation suggested that a normal flower was composed of calyx, petal, stamen and pistil (reduced to leaf-like carpel). While in proliferate flower, the leaf-like carpel continued to grow and was replaced by a new branch. Paraffin section indicated that the re-growth of leaf carpels might be the main reason for proliferate flower formation. Transcriptome sequencing of normal and proliferate flower was performed, and the expression levels of related genes were analysed. Among the differentially expressed genes, OfBFT-a and OfBFT-b had differential expression during the proliferate flower formation process. The expression patterns revealed that both OfBFT-a and OfBFT-b were highly accumulated in carpels, and were significantly downregulated during the proliferate flower development process. Subcellular localization indicated that OfBFT-a and OfBFT-b proteins were located in the nucleus. Functional studies in 'Tianxiang Taige' and Arabidopsis showed that OfBFT-a and OfBFT-b had important roles in floral organ development, especially the proliferate flower formation process by downregulating the accumulation of AG and SEP3 homologous genes. These results may shed new light on the study of proliferate flower formation and flower morphology breeding in flowering plants.

Function of LcAGL19 in the flowering regulation of Arabidopsis and Litchi chinensis

Litchi (Litchi chinensis Sonn.) is an important evergreen woody fruit tree. Appropriate low temperatures during autumn and winter are necessary for floral transition in litchi. However, global warming causes defective flowering, which seriously impedes the production of litchi. AGAMOUS-LIKE 19 (AGL19), a vernalization-related gene, had been found to control flowering time in Arabidopsis thaliana. However, its role in litchi remains unknown. In this study, we performed phylogenetic analysis. The results showed that LcAGL19 belonged to the SOC1/TM3-like protein family. Subcellular localization assay showed that LcAGL19 was localized on the nucleus. Ectopic expression of LcAGL19 in Arabidopsis thaliana resulted in early flowering, active inflorescence growth, and floral defects. Yeast two-hybrid assay and Firefly luciferase complementation imaging (LCI) assays showed that LcAGL19 might interact with MADS-box proteins to determine flowering time and floral organ identity. These results demonstrated that LcAGL19 might play important roles in floral transition, inflorescence and floral organ development in litchi. Our studies provided new insights into the regulation mechanisms of litchi flowering and offered meaningful references for AGL19 functional studies on other woody fruit trees. The functional study of LcAGL19 provided a genetic reference for litchi breeding.

Gene co-expression network analysis in areca floral organ and the potential role of the AcMADS17 and AcMADS23 in transgenic Arabidopsis

Areca catechu L., a monocot belonging to the palm family, is monoecious, with female and male flowers separately distributed on the same inflorescence. To discover the molecular mechanism of flower development in Areca, we sequenced different floral samples to generate tissue-specific transcriptomic profiles. We conducted a comparative analysis of the transcriptomic profiles of apical sections of the inflorescence with male flowers and the basal section of the inflorescence with female flowers. Based on the RNA sequencing dataset, we applied weighted gene co-expression network analysis (WGCNA) to identify sepal, petal, stamen, stigma and other specific modules as well as hub genes involved in specific floral organ development. The syntenic and expression patterns of AcMADS-box genes were analyzed in detail. Furthermore, we analyzed the open chromatin regions and transcription factor PI binding sites in male and female flowers by assay for transposase-accessible chromatin sequencing (ATAC-seq) assay. Heterologous expression revealed the important role of AcMADS17 and AcMADS23 in floral organ development. Our results provide a valuable genomic resource for the functional analysis of floral organ development in Areca.

Transcriptome sequencing and screening of genes related to the MADS-box gene family in Clematis courtoisii.

The MADS-box gene family controls plant flowering and floral organ development; therefore, it is particularly important in ornamental plants. To investigate the genes associated with the MADS-box family in Clematis courtoisii, we performed full-length transcriptome sequencing on C. courtoisii using the PacBio Sequel third-generation sequencing platform, as no reference genome data was available. A total of 12.38 Gb of data, containing 9,476,585 subreads and 50,439 Unigenes were obtained. According to functional annotation, a total of 37,923 Unigenes (75.18% of the total) were assigned with functional annotations, and 50 Unigenes were identified as MADS-box related genes. Subsequently, we employed hmmerscan to perform protein sequence similarity search for the translated Unigene sequences and successfully identified 19 Unigenes associated with the MADS-box gene family, including MIKC*(1) and MIKCC (18) genes. Furthermore, within the MIKCC group, six subclasses can be further distinguished.

AP3 promotes the synthesis of condensed tannin in fruit by positively regulating ANR expression

Condensed tannins are often found in fruits and nuts and have an astringent flavor. The synthesis pathway of condensed tannins is already clear, but few related regulatory factors have been explored. Previous studies about MADS-box transcription factors have mainly focused on the regulation of floral organ development. Recent studies have shown that MADS-box are also involved in fruit development, maturation, and quality. The fruit of Quercus fabri is rich in starch and nutrients in its kernel but is difficult to eat directly because of its high condensed tannin content. This study identified and functionally characterized the MADS-box transcription factor QfAP3 in Q. fabri. Functional analysis based on overexpression in Micro-Tom showed that QfAP3 promoted condensed tannin synthesis. By analyzing the expression trend of key genes in the condensed tannin synthesis pathway in Micro-Tom plants, we found that the expression trend of ANR was consistent with that of QfAP3, and QfAP3 could bind to the promoter of ANR and positively regulate it. This study has discovered new functions of MADS-box transcription factors in fruit quality formation, developed new regulatory factors for the synthesis pathway of condensed tannin, and provided a biotechnological method that can effectively reduce astringency in fruit.

IiAGL6 participates in the regulation of stamen development and pollen formation in Isatis indigotica

The AGL6 (AGMOUSE LIKE 6) gene is a member of the SEP subfamily and functions as an E-class floral homeotic gene in the development of floral organs. In this study, we cloned IiAGL6, the orthologous gene of AGL6 in Isatis indigotica. The constitutive expression of IiAGL6 in Arabidopsis thaliana resulted in a late-flowering phenotype and the development of curly leaves during the vegetative growth period. Abnormal changes in floral organ development were observed during the reproductive stage. In woad plants, suppression of IiAGL6 using TRV-VIGS (tobacco rattle virus-mediated virus-induced gene silencing) decreased the number of stamens and led to the formation of aberrant anthers. Similar changes in stamen development were also observed in miRNA-AGL6 transgenic Arabidopsis plants. Yeast two-hybrid and BiFC tests showed that IiAGL6 can interact with other MADS-box proteins in woad; thus, playing a key role in defining the identities of floral organs, particularly during stamen formation. These findings might provide novel insights and help investigate the biological roles of MADS transcription factors in I. indigotica.

Reliable reference gene selection for quantitative real-time PCR (qRT-PCR) in floral developmental phases of dioecious species Coccinia grandis

The flowering process is intricate and regulated by a combination of external and internal factors. Delving into gene expression research has the potential to enhance our comprehension of the molecular foundations underlying floral development. Because of its accuracy, specificity, reproducibility, and efficiency, qRT-PCR is now a biological research tool for studying expression pattern of desired genes. The gene expression investigations using qRT-PCR required a reference gene with relatively uniform expression levels in multiple biological samples, including different developmental stages, tissues, and experimental conditions. In this study, experimental sets offloral and floral organ development in the male and female plants of C. grandis, a dioecious Cucurbitaceae species, qRT-PCR profiling was performed using six reference genes as internal control with B-class floral identity gene, PISTILLATA (PI). To analyse the data, algorithms such as geNorm, NormFinder, RefFinder, and BestKeeper were used to pick out the best internal controls from a group of candidates. The optimal reference gene for qRT-PCR studies with floral samples has been recommended as β-actin combined with β-tubulin. This is the first report on the validation of candidate reference genes across flower developmental stages in the dioecious species C. grandis, which will provide basic data for research on the molecular mechanism underlying flower development in this species and lay the groundwork for similar studies in other related species.

Global gene expression profile and functional analysis reveal the conservation of reproduction-associated gene networks in Gossypium hirsutum.

Lastly, the bZIP gene family encompasses genes that have been reported to play a role in flower development, such as bZIP14 (FD). Notably, bZIP14 is essential for Flowering Locus T (FT) initiation of floral development in Arabidopsis (Abe et al. 2005). Cotton (Gossypium hirsutum L.) is the world's most extensively cultivated fiber crop. However, its reproductive development is poorly characterized at the molecular level. Thus, this study presents a detailed transcriptomic analysis of G. hirsutum at three different reproductive stages. We provide evidence that more than 64,000 genes are active in G. hirsutum during flower development, among which 94.33% have been assigned to functional terms and specific pathways. Gene set enrichment analysis (GSEA) revealed that the biological process categories of floral organ development, pollen exine formation, and stamen development were enriched among the genes expressed during the floral development of G. hirsutum. Furthermore, we identified putative Arabidopsis homologs involved in the G. hirsutum gene regulatory network (GRN) of pollen and flower development, including transcription factors such as WUSCHEL (WUS), INNER NO OUTER (INO), AGAMOUS-LIKE 66 (AGL66), SPOROCYTELESS/NOZZLE (SPL/NZZ), DYSFUNCTIONAL TAPETUM 1 (DYT1), ABORTED MICROSPORES (AMS), and ASH1-RELATED 3 (ASHR3), which are known crucial genes for plant reproductive success. The cotton MADS-box protein-protein interaction pattern resembles the previously described patterns for AGAMOUS (AG), SEEDSTICK (STK), SHATTERPROOF (SHP), and SEPALLATA3 (SEP3) homolog proteins from Arabidopsis. In addition to serving as a resource for comparative flower development studies, this work highlights the changes in gene expression profiles and molecular networks underlying stages that are valuable for cotton breeding improvement.

MADS1-regulated lemma and awn development benefits barley yield

Floral organ shape and size in cereal crops can affect grain size and yield, so genes that regulate their development are promising breeding targets. The lemma, which protects inner floral organs, can physically constrain grain growth; while the awn, a needle-like extension of the lemma, creates photosynthate to developing grain. Although several genes and modules controlling grain size and awn/lemma growth in rice have been characterized, these processes, and the relationships between them, are not well understood for barley and wheat. Here, we demonstrate that the barley E-class gene HvMADS1 positively regulates awn length and lemma width, affecting grain size and weight. Cytological data indicates that HvMADS1 promotes awn and lemma growth by promoting cell proliferation, while multi-omics data reveals that HvMADS1 target genes are associated with cell cycle, phytohormone signaling, and developmental processes. We define two potential targets of HvMADS1 regulation, HvSHI and HvDL, whose knockout mutants mimic awn and/or lemma phenotypes of mads1 mutants. Additionally, we demonstrate that HvMADS1 interacts with APETALA2 (A-class) to synergistically activate downstream genes in awn/lemma development in barley. Notably, we find that MADS1 function remains conserved in wheat, promoting cell proliferation to increase awn length. These findings extend our understanding of MADS1 function in floral organ development and provide insights for Triticeae crop improvement strategies.

Dynamic evolution of MADS-box genes in extant ferns via large-scale phylogenomic analysis.

Several studies of MADS-box transcription factors in flowering plants have been conducted, and these studies have indicated that they have conserved functions in floral organ development; MIKC-type MADS-box genes has been proved to be expanded in ferns, however, few systematic studies of these transcription factors have been conducted in non-seed plants. Although ferns and seed plants are sister groups, they exhibit substantial morphological differences. Here, we clarified the evolution of MADS-box genes across 71 extant fern species using available transcriptome, genome, and gene expression data. We obtained a total of 2,512 MADS-box sequences, ranging from 9 to 89 per species. The most recent common ancestor (MRCA) of ferns contained approximately three type I genes and at least 5-6 type II MADS-box genes. The domains, motifs, expression of type I and type II proteins, and the structure of the both type genes were conserved in ferns as to other land plants. Within type II genes, MIKC*-type proteins are involved in gametophyte development in ferns; MIKCC-type proteins have broader expression patterns in ferns than in seed plants, and these protein sequences are likely conserved in extant seed plants and ferns because of their diverse roles in diploid sporophyte development. More than 90% of MADS-box genes are type II genes, and MIKCC genes, especially CRM1 and CRM6-like genes, have undergone a large expansion in leptosporangiate ferns; the diverse expression patterns of these genes might be related to the fuctional diversification and increased complexity of the plant body plan. Tandem duplication of CRM1 and CRM6-like genes has contributed to the expansion of MIKCC genes. This study provides new insights into the diversity, evolution, and functions of MADS-box genes in extant ferns.

Advances in Floral Organ Development in Plants

Advances in Floral Organ Development in Plants

Transcriptome and genome-wide analysis of the potential role of SKP1 gene family in the development of floral organs of two related species of Allium fistulosum.

Allium fistulosum is an important plant germplasm resource, rich in nutrients and possessing unique medicinal value. However, due to its small floral organs, low seed setting rate of a single flower, high cost of artificial emasculation, and artificial pollination, the use of male sterile lines to prepare Allium hybrids has become a common choice. In this study, A. fistulosum var. viviparum Makino and A. galanthum were used as materials to study the regulation mechanism of anther development, aiming to provide a reference for male sterility. Through transcriptome differential gene screening and genome-wide bioinformatics analysis, 34 SKP1 (S-phase kinase-associated protein 1) genes (AfSKP1-1 to AfSKP1-34) were identified in the whole genome of A. fistulosum. The AfSKP1 genes are unevenly distributed on eight chromosomes. Furthermore, two pairs of collinear relationships are evident among family members, and fragment replication events between AfSKP1 genes have been identified. The phylogenetic tree analysis demonstrated that the AfSKP1, AtSKP1, OsSKP1, and SlSKP1 genes were clustered into six groups, exhibiting a gene structure analogous to that observed in members of an evolutionary classification. A combination of gene structure and phylogenetic analysis revealed the presence of cis-acting elements associated with growth, hormone regulation, and stress response within the AfSKP1 genes. Furthermore, expression analysis demonstrated that the AfSKP1 genes exhibited differential expression patterns across various tissues of A. fistulosum. The tissue-specific expression of the AfSKP1 gene was verified by Real-Time PCR. A comparison of the two materials revealed significant differences in the expression of the AfSKP1-8 gene in floral buds, the AfSKP1-11 gene in inflorescence meristems, and the AfSKP1-14 gene in inflorescence meristems, scapes, and floral buds. The results indicated that the three genes may be involved in anther development, thereby providing a theoretical basis for further study of floral organ development and pollen development in AfSKP1 family members.

Salt Stress Induces <i>SFT</i> Expression to Promote Early Flowering and Inhibits Floral Organ Development by Disturbing Cell Cycle in Tomato

Salt Stress Induces <i>SFT</i> Expression to Promote Early Flowering and Inhibits Floral Organ Development by Disturbing Cell Cycle in Tomato

Jujube Witches' Broom Phytoplasma Effector Zaofeng3, a Homologous Effector of SAP54, Induces Abnormal Floral Organ Development and Shoot Proliferation.

Plant-pathogenic phytoplasmas secrete specific virulence proteins into a host plant to modulate plant function for their own benefit. Identification of phytoplasmal effectors is a key step toward clarifying the pathogenic mechanisms of phytoplasma. In this study, Zaofeng3, also known as secreted jujube witches' broom phytoplasma protein 3 (SJP3), was a homologous effector of SAP54 and induced a variety of abnormal phenotypes, such as phyllody, malformed floral organs, witches' broom, and dwarfism in Arabidopsis thaliana. Zaofeng3 can also induce small leaves, dwarfism, and witches' broom in Ziziphus jujuba. Further experiments showed that the three complete α-helix domains predicted in Zaofeng3 were essential for induction of disease symptoms in jujube. Yeast two-hybrid library screening showed that Zaofeng3 mainly interacts with proteins involved in flower morphogenesis and shoot proliferation. Bimolecular fluorescence complementation assays confirmed that Zaofeng3 interacted with these proteins in the whole cell. Overexpression of zaofeng3 in jujube shoot significantly altered the expression patterns of ZjMADS19, ZjMADS47, ZjMADS48, ZjMADS77, and ZjTCP7, suggesting that overexpressing zaofeng3 might induce floral organ malformation and witches' broom by altering the expression of the transcriptional factors involved in jujube morphogenesis.

Genome-Wide Analysis of the MADS-Box Gene Family in Hibiscus syriacus and Their Role in Floral Organ Development.

Hibiscus syriacus belongs to the Malvaceae family, and is a plant with medicinal, edible, and greening values. MADS-box transcription factor is a large family of regulatory factors involved in a variety of biological processes in plants. Here, we performed a genome-wide characterization of MADS-box proteins in H. syriacus and investigated gene structure, phylogenetics, cis-acting elements, three-dimensional structure, gene expression, and protein interaction to identify candidate MADS-box genes that mediate petal developmental regulation in H. syriacus. A total of 163 candidate MADS-box genes were found and classified into type I (Mα, Mβ, and Mγ) and type II (MIKC and Mδ). Analysis of cis-acting elements in the promoter region showed that most elements were correlated to plant hormones. The analysis of nine HsMADS expressions of two different H. syriacus cultivars showed that they were differentially expressed between two type flowers. The analysis of protein interaction networks also indicated that MADS proteins played a crucial role in floral organ identification, inflorescence and fruit development, and flowering time. This research is the first to analyze the MADS-box family of H. syriacus and provides an important reference for further study of the biological functions of the MADS-box, especially in flower organ development.