Floral Expression Research Articles

Native and introduced pollinators vary in their seasonal floral resource visitation and selection between native and exotic plant species

Abstract Anthropogenic pressures on native ecosystems have resulted in numerous functional and compositional changes, creating novel ecosystems with new interactions between native and exotic species. How native species utilize these resources is crucial for their management in altered landscapes and the promotion of their essential ecosystem services. We compared seasonal floral selection between European honey bees and their most phylogenetically similar native component in our study region, bumble bees, in North American grasslands with high densities of exotic plant species. Additionally, we determined whether floral species richness, total flowering density, native floral density or exotic floral density best explained the abundance of both groups. Selection analyses revealed that honey bees and native bumble bees differed in selection between native and non‐native floral resource availability, with any significant selection of honey bees being for exotic plants while native bumble bees selected for native plants. Native forb presence and floral richness best explained the variation in bumble bee abundance, while honey bee abundance was associated with flowering densities in the early and mid‐seasons and floral richness in both the early and late seasons. Despite their generalist diets, we emphasize the importance of native floral availability for bumble bee foraging in novel grassland landscapes and the importance of exotic plants to support honey bee production. Synthesis and applications. Our results indicate that pollinator forage management should differ for non‐native and native species, despite morphological and life‐history similarities. However, greater floral diversity provides a common management focus that can benefit honey bees and bumble bees in particular seasonal periods. Our results suggest that management actions promoting resource diversity can benefit functionally different species. In grasslands, implementing disturbance processes that can favour floral expression (e.g. fire; grazing) can support bumble bees of conservation concern and agriculturally important bees simultaneously.

Homotypic Clusters of Transcription Factor Binding Sites in the First Large Intron of AGL24 MADS-Box Transcription Factor Are Recruited in the Enhancement of Floral Expression

The occurrence of homotypic clusters of transcription factor binding sites (HCTs) and their contribution to regulatory evolution is documented in animals, but their manifestation in regulating plant genome expression remained an enigma. To explore the existence and functions of HCTs in highly constrained non-coding sequences of MADS-box transcription factors—generally involved in floral organ identity and phase transition—we employed cis-regulatory cluster finding in silico tools augmented with in vitro assays and site-directed mutagenesis in the STMADS11 superclade of this family. Thousands of transcription factor binding sites (TFBSs) organized into HCTs and multiple-factor binding elements belonging to various families of TFs were identified in the promoter as well as in the intronic region of the selected members of STMADS11 subfamily. A total of 151 HCTs were detectable in the defined promoter in comparison with 144 in the intronic regions. The MADS-domain binding HCTs (overlapping CArG-boxes) constitute a major portion (18%) of these HCTs. A protrusive HCT of 11 TFBSs was identified in the 1st large intron of the AGAMOUS LIKE 24 (AGL24) pertinent to the SVP clade of the STMADS11 subfamily but no such cluster could be detected in the region proximal to the core promoter. These HCTs in the intronic region could bind the SEP4 MADS-domain protein as revealed by in vitro assay. Using HCT cluster swapping of CArG-boxes through the GUS reporter assay, it was possible to empirically validate that a change in the position of intronic MADS-box cluster of AGL24 to the promoter region adjacent to the transcriptional start site (TSS) invoke an enhancement of floral expression. This study unveils the occurrence of HCTs in both the promoter and downstream intronic regions in the selected members of the STMADS11 subfamily of plants. These HCTs play an important role in deciphering the gene regulatory code of MADS-box TFs particularly AGL24.

Transcriptomic analysis of field-grown rice (Oryza sativa L.) reveals responses to shade stress in reproductive stage

The number of spikelets per panicle is a key factor affecting rice (Oryza sativa L.) yield, and is regulated by many different environmental cues, such as light intensity. In this study, we found that shade led to a reduction in the number of secondary branches and fewer spikelets per panicle. Rice grown in the shade had an increased spikelet degradation rate. We studied the genes that respond to shade in rice using transcriptome sequencing, which revealed that rice floral genes OsFKF1 and OsDof12 expression levels were suppressed by shading. However, Heading date 1 (Hd1), Heading date 3a (Hd3a), and Early heading date 1 (Ehd1) were induced and RICE FLOWERING LOCUS T 1 (RFT1) was suppressed without any obvious change in heading time. Furthermore, the expression level of spikelet differentiation-related genes OsFOR1, FON1, OsPBP1 and OsSPL16 were influenced by shade stress, may led to changes in spike structural. Shade affected the expression of growth-related genes that are involved in metabolism, DNA synthesis/chromatin structure, and the environmental adaptation pathway. Genes involved in chloroplast development were downregulated in leaves under shade. In addition, genes that regulate energy expenditure were suppressed by shade in both young panicles and leaves, indicating that damage to the leaf photosynthetic apparatus reduces the energetic costs of the plant. Organic synthesis-related genes were suppressed in young panicles of plants under shade, suggesting that shade slows panicle development. The identification of novel differentially expressed genes provides new insights into the effects of light deficiency on young panicle development in rice.

Tobacco TTG2 and ARF8 function concomitantly to control flower colouring by regulating anthocyanin synthesis genes.

Recently we elucidated that tobacco TTG2 cooperates with ARF8 to regulate the vegetative growth and seed production. Here we show that TTG2 and ARF8 control flower colouring by regulating expression of ANS and DFR genes, which function in anthocyanin biosynthesis. Genetic modifications that substantially altered expression levels of the TTG2 gene and production quantities of TTG2 protein were correlated with flower development and colouring. Degrees of flower colour were increased by TTG2 overexpression but decreased through TTG2 silencing, in coincidence with high and low concentrations of anthocyanins in flowers. Of five genes involved in the anthocyanin biosynthesis pathway, only ANS and DFR were TTG2-regulated and displayed enhancement and diminution of expression with TTG2 overexpression and silencing, respectively. The floral expression of ANS and DFR also needed a functional ARF8 gene, as ANS and DFR expression were attenuated by ARF8 silencing, which concomitantly diminished the role of TTG2 in anthocyanin production. While ARF8 required TTG2 to be expressed by itself and to regulate ANS and DFR expression, the concurrent presence of normally functional TTG2 and ARF8 was critical for floral production of anthocyanins and also for flower colouration. Our data suggest that TTG2 functions concomitantly with ARF8 to control degrees of flower colour by regulating expression of ANS and DFR, which are involved in the anthocyanin biosynthesis pathway. ARF8 depends on TTG2 to regulate floral expression of ANS and DFR with positive effects on anthocyanin production and flower colour.

Floral expression and pollen germination ability in productive mountain papaya (Vasconcellea pubescens A.DC.) orchards

Mountain papaya (Vasconcellea pubescens A.DC.) is described as trioecious in the centers of origin of Ecuador, Colombia, and Peru. However, under cultivation conditions in La Serena (30° S, 70° W), Chile, it is found to be dioecious and monoecious. The objective was to learn about the variations in floral expression of mountain papaya. Flowers from monoecious and dioecious plants were therefore identified and quantified during two seasons. In vitro pollen germination ability was also evaluated based on the factors of site, season, and plant sex. Monoecious plant inflorescences are polygamous; female and male flowers are observed, as well as bisexual flowers that are usually deformed. This condition allows them to be classified as an ambisexual plant. The existence of flowers of different sexes appears to depend on the season; the female dioecious plant is maintained as such, independently of climatic conditions. Pollen from male flowers, from both ambisexual and male plants, germinates 75% in summer, while germination decreases to 56% in spring (P ≤ 0.05). Flowering of female plants coincides with the permanent occurrence of male flowers in ambisexual plants, which ensures pollination without the need for male plants as pollinators in orchards. Based on this information, some management practices and possible lines of research about this species are proposed.

Analysis of Floral Fragrance Expression Pattern of Wind Orchids (Sedirea japonica) by Using Electronic Nose and GC/MS

Analysis of Floral Fragrance Expression Pattern of Wind Orchids (Sedirea japonica) by Using Electronic Nose and GC/MS

FlowerNet: a gene expression correlation network for anther and pollen development.

Floral formation, in particular anther and pollen development, is a complex biological process with critical importance for seed set and for targeted plant breeding. Many key transcription factors regulating this process have been identified; however, their direct role remains largely unknown. Using publicly available gene expression data from Arabidopsis (Arabidopsis thaliana), focusing on those studies that analyze stamen-, pollen-, or flower-specific expression, we generated a network model of the global transcriptional interactions (FlowerNet). FlowerNet highlights clusters of genes that are transcriptionally coregulated and therefore likely to have interacting roles. Focusing on four clusters, and using a number of data sets not included in the generation of FlowerNet, we show that there is a close correlation in how the genes are expressed across a variety of conditions, including male-sterile mutants. This highlights the important role that FlowerNet can play in identifying new players in anther and pollen development. However, due to the use of general floral expression data in FlowerNet, it also has broad application in the characterization of genes associated with all aspects of floral development and reproduction. To aid the dissection of genes of interest, we have made FlowerNet available as a community resource (http://www.cpib.ac.uk/anther). For this resource, we also have generated plots showing anther/flower expression from a variety of experiments: These are normalized together where possible to allow further dissection of the resource.

Consequences of Whole-Genome Triplication as Revealed by Comparative Genomic Analyses of the Wild Radish Raphanus raphanistrum and Three Other Brassicaceae Species.

Polyploidization events are frequent among flowering plants, and the duplicate genes produced via such events contribute significantly to plant evolution. We sequenced the genome of wild radish (Raphanus raphanistrum), a Brassicaceae species that experienced a whole-genome triplication event prior to diverging from Brassica rapa. Despite substantial gene gains in these two species compared with Arabidopsis thaliana and Arabidopsis lyrata, ∼70% of the orthologous groups experienced gene losses in R. raphanistrum and B. rapa, with most of the losses occurring prior to their divergence. The retained duplicates show substantial divergence in sequence and expression. Based on comparison of A. thaliana and R. raphanistrum ortholog floral expression levels, retained radish duplicates diverged primarily via maintenance of ancestral expression level in one copy and reduction of expression level in others. In addition, retained duplicates differed significantly from genes that reverted to singleton state in function, sequence composition, expression patterns, network connectivity, and rates of evolution. Using these properties, we established a statistical learning model for predicting whether a duplicate would be retained postpolyploidization. Overall, our study provides new insights into the processes of plant duplicate loss, retention, and functional divergence and highlights the need for further understanding factors controlling duplicate gene fate.

Corolla chirality inHypericum irazuenseandH. costaricense(Hypericaceae): parallels with monomorphic enantiostyly1

Abstract Symmetry is an important floral character and is often associated with the degree of pollination specialization. Typically floral symmetry is fixed within a species. Rotational symmetry occurs in two different corolla variations according to the direction in which the petals overlap. This study describes the pattern of polymorphism in corolla chirality of Hypericum irazuense Kuntze ex. N. Robson and H. costaricense N. Robson. The individuals of these species exhibit flowers with corollas that rotate either counter clockwise (left/sinistrorse) or clockwise (right/dextrorse). Studying this pattern of floral expression is the first step in gaining a better understanding of whether this trait polymorphism is maintained due to an adaptive advantage or as a byproduct of a developmental genetic constraint. We quantified the proportion of dextrorse and sinistrorse flowers for H. irazuense and H. costaricense. We also examined whether the chirality of a flower is independent of the corolla chirality of it...

Deciphering the Physalis floridana Double-Layered-Lantern1 Mutant Provides Insights into Functional Divergence of the GLOBOSA Duplicates within the Solanaceae

Physalis spp. develop the "Chinese lantern" trait, also known as inflated calyx syndrome, that is a morphological novelty. Here, we identified the double-layered-lantern1 (doll1) mutant, a recessive and monofactorial mutation, in Physalis floridana; its corolla and androecium were transformed into the calyx and gynoecium, respectively. Two GLOBOSA-like MADS-box paralogous genes PFGLO1 and PFGLO2 were found in Physalis floridana, while the mutated phenotype was cosegregated with a large deletion harboring PFGLO1 and was complemented by the PFGLO1 genomic locus in transgenic plants, and severe PFGLO1 knockdowns phenocopied doll1. Thus, DOLL1 encodes the PFGLO1 protein and plays a primary role in determining corolla and androecium identity. However, specific PFGLO2 silencing showed no homeotic variation but rather affected pollen maturation. The two genes featured identical floral expression domains, but the encoding proteins shared 67% identity in sequences. PFGLO1 was localized in the nucleus when expressed in combination with a DEFICIENS homolog from Physalis floridana, whereas PFGLO2 was imported to the nucleus on its own. The two proteins were further found to have evolved different interacting partners and regulatory patterns, supporting the hypothesis that PFGLO2 is functionally separated from organ identity. Such a divergent pattern of duplicated GLO genes is unusual within the Solanaceae. Moreover, the phenotypes of the PFGLO1PFGLO2 double silencing mutants suggested that PFGLO2, through genetically interacting with PFGLO1, also exerts a role in the control of organ number and tip development of the second floral whorl. Our results, therefore, shed new light on the functional evolution of the duplicated GLO genes.

The involvement of phytohormones in the plant sex regulation

The data concerning the plant sex regulation by phytohormones are presented. Functioning of signaling pathways regulating floral development and sex expression, including those with phytohormone involvement, are considered. The role of phytohormones in the functioning of systems and mechanisms of sex regulation is analyzed. The examples of sex reversion by plant treatment with phytohormones are presented. It is demonstrated that many genes determining sex encode proteins involved in the phytohormone metabolism. The significance of phytohormone investigation for the understanding of molecular mechanisms of plant sex regulation is discussed.

Random Sample

A sunflower is more than just a pretty face: It's a floral expression of the so-called Fibonacci sequence—1, 1, 2, 3, 5, 8, and so on, where each number is the sum of the two preceding numbers in the series. And now, a U.K.-based project is enlisting the help of gardeners around the world to help test a theory that originated with one of history's greatest mathematicians, Alan Turing.

Effect of environment and shoot architecture on floral transition and gene expression in Eucalyptus occidentalis and Metrosideros excelsa

Metrosiderosexcelsa and Eucalyptus occidentalis exhibit different strategies prior to flowering—the former passes through a long juvenile phase and must acquire a degree of architectural complexity to flower, whereas the latter flowers precociously even on stems still exhibiting juvenile foliage. As expediting flowering is of interest to breeders and horticulturalists alike we compared these species by growing plants with two branch architecture treatments in factorial combination with two growth environments. Plants were either allowed to branch freely or constrained to a single stem before subsequently being allowed to branch; one environment was inductive for flowering and the other not. Three meristem identity genes (the equivalents of LEAFY, APETALA1 and TERMINAL FLOWER1) were used as indicators of flowering. Constraining E. occidentalis plants to a single stem delayed the onset of the main flush of flowering in contrast to M. excelsa, although in both species a complex interaction between branching and environment occurred. We show that the complexity of the architecture can impact on production of flowers and can be used to expedite or enhance flowering for breeding purposes, but this is dependent on the species. AP1 appears to be a useful marker not just for floral organ differentiation but also as an indicator of floral induction having occurred.

Evolutionary trends in the floral transcriptome: insights from one of the basalmost angiosperms, the water lily Nuphar advena (Nymphaeaceae)

Current understanding of floral developmental genetics comes primarily from the core eudicot model Arabidopsis thaliana. Here, we explore the floral transcriptome of the basal angiosperm, Nuphar advena (water lily), for insights into the ancestral developmental program of flowers. We identify several thousand Nuphar genes with significantly upregulated floral expression, including homologs of the well-known ABCE floral regulators, deployed in broadly overlapping transcriptional programs across floral organ categories. Strong similarities in the expression profiles of different organ categories in Nuphar flowers are shared with the magnoliid Persea americana (avocado), in contrast to the largely organ-specific transcriptional cascades evident in Arabidopsis, supporting the inference that this is the ancestral condition in angiosperms. In contrast to most eudicots, floral organs are weakly differentiated in Nuphar and Persea, with staminodial intermediates between stamens and perianth in Nuphar, and between stamens and carpels in Persea. Consequently, the predominantly organ-specific transcriptional programs that characterize Arabidopsis flowers (and perhaps other eudicots) are derived, and correlate with a shift towards morphologically distinct floral organs, including differentiated sepals and petals, and a perianth distinct from stamens and carpels. Our findings suggest that the genetic regulation of more spatially discrete transcriptional programs underlies the evolution of floral morphology.

Comparative transcriptomics among floral organs of the basal eudicot Eschscholzia californica as reference for floral evolutionary developmental studies

BackgroundMolecular genetic studies of floral development have concentrated on several core eudicots and grasses (monocots), which have canalized floral forms. Basal eudicots possess a wider range of floral morphologies than the core eudicots and grasses and can serve as an evolutionary link between core eudicots and monocots, and provide a reference for studies of other basal angiosperms. Recent advances in genomics have enabled researchers to profile gene activities during floral development, primarily in the eudicot Arabidopsis thaliana and the monocots rice and maize. However, our understanding of floral developmental processes among the basal eudicots remains limited.ResultsUsing a recently generated expressed sequence tag (EST) set, we have designed an oligonucleotide microarray for the basal eudicot Eschscholzia californica (California poppy). We performed microarray experiments with an interwoven-loop design in order to characterize the E. californica floral transcriptome and to identify differentially expressed genes in flower buds with pre-meiotic and meiotic cells, four floral organs at pre-anthesis stages (sepals, petals, stamens and carpels), developing fruits, and leaves.ConclusionsOur results provide a foundation for comparative gene expression studies between eudicots and basal angiosperms. We identified whorl-specific gene expression patterns in E. californica and examined the floral expression of several gene families. Interestingly, most E. californica homologs of Arabidopsis genes important for flower development, except for genes encoding MADS-box transcription factors, show different expression patterns between the two species. Our comparative transcriptomics study highlights the unique evolutionary position of E. californica compared with basal angiosperms and core eudicots.

Conserved Functions of Arabidopsis and Rice CC-Type Glutaredoxins in Flower Development and Pathogen Response

Glutaredoxins (GRXs) are ubiquitous oxidoreductases that play a crucial role in response to oxidative stress by reducing disulfides in various organisms. In planta, three different GRX classes have been identified according to their active site motifs. CPYC and CGFS classes are found in all organisms, whereas the CC-type class is specific for higher land plants. Recently, two Arabidopsis CC-type GRXs, ROXY1 and ROXY2, were shown to exert crucial functions in petal and anther initiation and differentiation. To analyze the function of CC-type GRXs in the distantly related monocots, we isolated and characterized OsROXY1 and OsROXY2-two rice homologs of ROXY1. Both genes are expressed in vegetative and reproductive stages. Although rice flower morphology is distinct from eudicots, OsROXY1/2 floral expression patterns are similar to their Arabidopsis counterparts ROXY1/2. Complementation experiments demonstrate that OsROXY1 and OsROXY2 can fully rescue the roxy1 floral mutant phenotype. Overexpression of OsROXY1, OsROXY2, and ROXY1 in Arabidopsis causes similar vegetative and reproductive plant developmental defects. ROXY1 and its rice homologs thus exert a conserved function during eudicot and monocot flower development. Strikingly, overexpression of these CC-type GRXs also leads to an increased accumulation of hydrogen peroxide levels and hyper-susceptibility to infection from the necrotrophic pathogen Botrytis cinerea, revealing the importance of balanced redox processes in flower organ development and pathogen defence.

Roles of CmFL, CmAFL1, and CmSOC1 in the transition from vegetative to reproductive growth in Chrysanthemum morifolium Ramat.

SummaryThe transition from vegetative to reproductive growth is marked by the termination of vegetative development and adoption of a floral identity by the shoot apical meristem. This process is called the floral transition. To elucidate the molecular determinants involved in this process in chrysanthemum (Chrysanthemum morifolium Ramat.), we isolated the following three floral identity and/or integrator genes from plants: CmFL, a homologue of FLORICAULA (FLO)/LEAFY (LFY); CmAFL1, a member of the APETALA1 (AP1)/FRUITFULL (FUL) sub-family; and CmSOC1, a member of the SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) sub-family. Up-regulated expression of CmFL in Arabidopsis resulted in an early-flowering phenotype. Our data show significant up-regulation of expression of all three of the above-mentioned genes and a strong correlation between the floral transition and gene expression under three different photoperiodic conditions. This study strongly suggests that CmFL, CmAFL1, and CmSOC1 are involved in the transition from vegetative to reproductive growth, and are activated co-ordinately after the floral transition in early-developing inflorescences in chrysanthemum.

A spatial dissection of the Arabidopsis floral transcriptome by MPSS

BackgroundWe have further characterized floral organ-localized gene expression in the inflorescence of Arabidopsis thaliana by comparison of massively parallel signature sequencing (MPSS) data. Six libraries of RNA sequence tags from immature inflorescence tissues were constructed and matched to their respective loci in the annotated Arabidopsis genome. These signature libraries survey the floral transcriptome of wild-type tissue as well as the floral homeotic mutants, apetala1, apetala3, agamous, a superman/apetala1 double mutant, and differentiated ovules dissected from the gynoecia of wild-type inflorescences. Comparing and contrasting these MPSS floral expression libraries enabled demarcation of transcripts enriched in the petals, stamens, stigma-style, gynoecia, and those with predicted enrichment within the sepal/sepal-petals, petal-stamens, or gynoecia-stamens.ResultsBy comparison of expression libraries, a total of 572 genes were found to have organ-enriched expression within the inflorescence. The bulk of characterized organ-enriched transcript diversity was noted in the gynoecia and stamens, whereas fewer genes demonstrated sepal or petal-localized expression. Validation of the computational analyses was performed by comparison with previously published expression data, in situ hybridizations, promoter-reporter fusions, and reverse transcription PCR. A number of well-characterized genes were accurately delineated within our system of transcript filtration. Moreover, empirical validations confirm MPSS predictions for several genes with previously uncharacterized expression patterns.ConclusionThis extensive MPSS analysis confirms and supplements prior microarray floral expression studies and illustrates the utility of sequence survey-based expression analysis in functional genomics. Spatial floral expression data accrued by MPSS and similar methods will be advantageous in the elucidation of more comprehensive genetic regulatory networks governing floral development.

Control of corolla monosymmetry in the Brassicaceae Iberis amara

Establishment of morphological novelties has contributed to the enormous diversification of floral architecture. One such novelty, flower monosymmetry, is assumed to have evolved several times independently during angiosperm evolution. To date, analysis of monosymmetry regulation has focused on species from taxa where monosymmetry prevails, such as the Lamiales and Fabaceae. In Antirrhinum majus, formation of a monosymmetric corolla is specified by the activity of the TCP transcription factors CYCLOIDEA (CYC) and DICHOTOMA (DICH). It was shown that establishment of monosymmetry likely requires an early asymmetric floral expression of CYC homologs that needs to be maintained until late floral stages. To understand how CYC homologs might have been recruited during evolution to establish monosymmetry, we characterized the likely CYC ortholog IaTCP1 from Iberis amara (Brassicaceae). Species of the genus Iberis form a monosymmetric corolla, whereas the Brassicaceae are otherwise dominated by genera developing a polysymmetric corolla. Instead of four equally sized petals, I. amara produces two small adaxial and two large abaxial petals. The timing of IaTCP1 expression differs from that of its Arabidopsis homolog TCP1 and other CYC homologs. IaTCP1 lacks an asymmetric early expression but displays a very strong differential expression in the corolla at later floral stages, when the strongest unequal petal growth occurs. Analysis of occasionally occurring peloric Iberis flower variants and comparative functional studies of TCP homologs in Arabidopsis demonstrate the importance of an altered temporal IaTCP1 expression within the Brassicaceae to govern the formation of a monosymmetric corolla.

A conserved microRNA module exerts homeotic control over Petunia hybrida and Antirrhinum majus floral organ identity

It is commonly thought that deep phylogenetic conservation of plant microRNAs (miRNAs) and their targets indicates conserved regulatory functions. We show that the blind (bl) mutant of Petunia hybrida and the fistulata (fis) mutant of Antirrhinum majus, which have similar homeotic phenotypes, are recessive alleles of two homologous miRNA-encoding genes. The BL and FIS genes control the spatial restriction of homeotic class C genes to the inner floral whorls, but their ubiquitous early floral expression patterns are in contradiction with a potential role in patterning C gene expression. We provide genetic evidence for the unexpected function of the MIRFIS and MIRBL genes in the center of the flower and propose a dynamic mechanism underlying their regulatory role. Notably, Arabidopsis thaliana, a more distantly related species, also contains this miRNA module but does not seem to use it to confine early C gene expression to the center of the flower.