Petal Cells Research Articles

Assessment of the authenticity of horse chestnut (Aesculus hippocastanum L.) flowers by scanning electron microscopy

Introduction. Horse chestnut (Aesculus hippocastanum L.) is a plant widely used in official and folk medicine in many countries. Pharmacopoeia raw materials in the Russian Federation are only horse chestnut seeds. Flowers, due to the fraction of phenolic derivatives and triterpene saponins contained in them, are a promising medicinal plant raw material, presumably having a venotonizing and membrane-protective effect. To obtain medicinal herbal preparations based on horse chestnut flowers, it is required to have regulatory documentation containing a list of quality indicators, including a description of the signs of its authenticity (morphology and anatomy). Scanning electron microscopy is one of the advanced methods that have recently been increasingly used in medicine and pharmacognostic analysis. Unlike light microscopy, the method provides a three-dimensional spatial representation of diagnostically significant signs of medicinal plant raw materials.Aim. The aim of the study was to study the morphology of the surface of horse chestnut flowers by scanning electron microscopy.Materials and methods. The object of the study was dried whole flowers of horse chestnut (Aesculus hippocastanum L.), collected in the Voronezh region in 2023 at the beginning of flowering. The pieces of flowers were pre-sprayed with silicon on an automatic spraying unit Q150R ES (Quorum Technologies Ltd., Great Britain). Micrographs were obtained using the JSM-6510LV electron microscope (JEOL Ltd., Japan).Results and discussion. The micrographs obtained during the analysis showed diagnostically significant features of the flower structure: the epidermal cells of the corolla petals are polygonal, irregularly shaped, some elongated with sinuous folds. Pollen grains can be collected in cluster-like clusters, located separately or found singly. The surface of the corolla petal is covered with numerous often twisting hairs having a rough-warped structure and a cone-shaped base with a clearly defined attachment point. The surface of the staminate filaments is striated, with longitudinal folds with single unicellular hairs. The anther has a folded shape, its surface is lined with scaly epidermal cells with rough and thickened walls. The surface of the calyx, including the pedicel, is also densely pubescent with numerous trichomes.Conclusion. The scanning electron microscopy method was used for the first time to study the morphological and anatomical features of horse chestnut flowers. The structure of the main diagnostically significant structures of this LRS has been clarified. The morphology of the epidermis surface of the petals of the corolla and calyx, trichomes, pollen filaments, anthers and pollen grains of flowers has been determined. It has been established that carbon and oxygen are the predominant elements of the raw materials.

Structural changes in Nelumbo flower petals during opening and closing.

Nelumbo nucifera is one of several plant species with flowers that typically open in the early morning and close by noon. This movement normally repeats for 3 days, with all petals falling off on day 4. However, detailed observations of flower movement in Nelumbo species are limited. Movement of flowers on plants in growth chambers were observed using time-lapse photography. Petals were examined with scanning electron microscopy or fixed and sectioned for light microscopy to determine whether changes in cell size contribute to petal elongation during flowering. This study is the first to microscopically observe petal cells of a Nelumbo species during flowering in controlled conditions. Petals elongated during the 4-day flowering period. Inner petals were more elongated than the outer petals. Among the basal, central, and tip regions of a single petal, the cells in the basal region enlarged the most. Outer and inner epidermal cells in the basal region of the inner petals, on both adaxial and abaxial sides, gradually enlarged during the flowering period through cycles of repeated increases as the petals opened and decreases as they closed. Petals opened and closed repeatedly as they elongated, primarily in their basal region. Cells in the basal region of the petal on the adaxial and abaxial sides periodically fluctuated in size, increased during flower opening and decreased during closing, but differences in these patterns were observed between the two sides, suggesting that one of the driving forces behind the opening and closing of flowers of Nelumbo species is the increase and decrease in the size of the petal cells.

A feedback loop comprising RhMYB114 and RhMYB16 regulates anthocyanin accumulation and tissue acidification in Rosa hybrida

Coloration in rose (Rosa hybrida) petals is primarily determined by anthocyanin accumulation in vacuoles, and vacuolar acidification plays a central role in controlling the accumulation of this pigment. Nevertheless, the regulatory interplay between anthocyanin accumulation and tissue acidification processes remains somewhat unclear. The present study characterized an activator RhMYB114 and a repressor RhMYB16, which functioned synergistically in anthocyanin accumulation and tissue acidification in rose. Transforming tobacco and roses by overexpression, the introduction of RhMYB114 resulted in an increase in anthocyanin levels and a noticeable decrease in pH in the petal cells of both rose and tobacco, whereas RhMYB16 introduction led to inverse effects. To further clarify the underlying the regulatory mechanisms, the yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC) and dual-luciferase (LUC) were employed. The results showed that RhMYB16 competed with RhMYB114, bound to RhbHLH3 or RhbHLH33, and inhibited its ability to induce the expression of genes related to anthocyanin biosynthesis and acidification. Our findings revealed a feedback mechanism for the regulation of anthocyanin synthesis and tissue acidification involving RhMYB114, which stimulated the transcriptional expression of RhMYB16, whose encoded protein RhMYB16, in turn, negatively regulated the transcriptional expression of RhMYB114. Therefore, this study underscores the pivotal roles of the RhMYB114–RhMYB16 loop in regulating anthocyanin synthesis and tissue acidification, offering insights into metabolic manipulation to enhance the aesthetic appeal of roses.

Cytosolic acidification and oxidation are the toxic mechanisms of SO2 in Arabidopsis guard cells.

SO2/H2SO3 can damage plants. However, its toxic mechanism has still been controversial. Two models have been proposed, cytosolic acidification model and cellular oxidation model. Here, we assessed the toxic mechanism of H2SO3 in three cell types of Arabidopsis thaliana, mesophyll cells, guard cells and petal cells. The sensitivity of guard cells of CHLORIDE CHANNEL a (CLCa)-knockout mutants to H2SO3 was significantly lower than those of wildtype plants. Expression of other CLC genes in mesophyll cells and petal cells were different from guard cells. Treatment with antioxidant, disodium 4,5-dihydroxy-1,3-benzenedisulfonate (tiron), increased the median lethal concentration (LC50) of H2SO3 in guard cells indicating the involvement of cellular oxidation, while the effect was negligible in mesophyll cells and petal cells. These results indicate that there are two toxic mechanisms of SO2 to Arabidopsis cells: cytosolic acidification and cellular oxidation, and the toxic mechanism may vary among cell types.

Signalling cascades choreographing petal cell death: implications for postharvest quality.

Senescence is a multifaceted and dynamic developmental phase pivotal in the plant's lifecycle, exerting significant influence and involving intricate regulatory mechanisms marked by a variety of structural, biochemical and molecular alterations. Biochemical changes, including reactive oxygen species (ROS) generation, membrane deterioration, nucleic acid degradation and protein degradation, characterize flower senescence. The progression of senescence entails a meticulously orchestrated network of interconnected molecular mechanisms and signalling pathways, ensuring its synchronized and efficient execution. Within flowering plants, petal senescence emerges as a crucial aspect significantly impacting flower longevity and postharvest quality, emphasizing the pressing necessity of unravelling the underlying signalling cascades orchestrating this process. Understanding the complex signalling pathways regulating petal senescence holds paramount importance, not only shedding light on the broader phenomenon of plant senescence but also paving the way for the development of targeted strategies to enhance the postharvest longevity of cut flowers. Various signalling pathways participate in petal senescence, encompassing hormone signalling, calcium signalling, protein kinase signalling and ROS signalling. Among these, the ethylene signalling pathway is extensively studied, and the manipulation of genes associated with ethylene biosynthesis or signal transduction has demonstrated the potential to enhance flower longevity. A thorough understanding of these complex pathways is critical for effectively delaying flower senescence, thereby enhancing postharvest quality and ornamental value. Therefore, this review adopts a viewpoint that combines fundamental research into the molecular intricacies of senescence with a practical orientation towards developing strategies for improving the postharvest quality of cut flowers. The innovation of this review is to shed light on the pivotal signalling cascades underpinning flower senescence and offer insights into potential approaches for modulating these pathways to postpone petal senescence in ornamental plants.

Characterisation of the R2R3 Myb subgroup 9 family of transcription factors in tomato.

Tomato (Solanum lycopersicum) has many epidermal cell outgrowths including conical petal cells and multiple types of trichomes. These include the anther-specific trichome mesh which holds the anthers connate. The R2R3 Myb Subgroup 9 family of transcription factors is involved in development of epidermal cell outgrowths throughout the angiosperms. No previous study has examined all members of this transcription factor family in a single species. All 7 R2R3 Myb Subgroup 9 genes were isolated from tomato. They were ectopically expressed in tobacco to assess their ability to induce epidermal cell outgrowth. Endogenous expression patterns were examined by semi-quantitative RT-PCR at different stages of floral development relative to the development of anther trichomes. We report variation in the degree of epidermal cell outgrowth produced in transgenic tobacco by each ectopically expressed gene. Based on expression profile and ectopic activity, SlMIXTA-2 is likely involved in the production of leaf trichomes. SlMIXTA-2 is expressed most strongly in the leaves, and not expressed in the floral tissue. SlMYB17-2 is the best candidate for the regulation of the anther trichome mesh. SlMYB17-2 is expressed strongly in the floral tissue and produces a clear phenotype of epidermal cell outgrowths when ectopically expressed in tobacco. Analysis of the phenotypes of transgenic plants ectopically expressing all 7 genes has revealed the different extent to which members of the same transcription factor subfamily can induce cellular outgrowth.

EXPANSIN15 is involved in flower and fruit development in Arabidopsis

Key messageEXPANSIN15 is involved in petal cell morphology and size, the fusion of the medial tissues in the gynoecium and expansion of fruit valve cells. It genetically interacts with SPATULA and FRUITFULL.Cell expansion is fundamental for the formation of plant tissues and organs, contributing to their final shape and size during development. To better understand this process in flower and fruit development, we have studied the EXPANSIN15 (EXPA15) gene, which showed expression in petals and in the gynoecium. By analyzing expa15 mutant alleles, we found that EXPA15 is involved in petal shape and size determination, by affecting cell morphology and number. EXPA15 also has a function in fruit size, by affecting cell size and number. Furthermore, EXPA15 promotes fusion of the medial tissues in the gynoecium. In addition, we observed genetic interactions with the transcription factors SPATULA (SPT) and FRUITFULL (FUL) in gynoecium medial tissue fusion, style and stigma development and fruit development in Arabidopsis. These findings contribute to the importance of EXPANSINS in floral and fruit development in Arabidopsis.

Insights into the functional role of tomato TM6 as a transcriptional regulator of flower development.

Flower development is a crucial step towards the completion of the plant life cycle. Physiological processes and gene regulatory mechanisms underlying flower formation have been extensively characterized, and the implication of MADS-box transcription factors as primary regulators of flower morphology has been widely described, mainly due to the analysis of loss-of-function mutants in model species. Nevertheless, detailed characterization of allele variation in several MADS-box homologous genes from crop species remains undescribed. Here, we have characterized a tomato mutant with aberrant flower development. Mutant plants exhibit changes in petal cell identity, as well as homeotic transformations of stamens into carpelloid structures, which in most cases result in succulent organs. Molecular analysis proved that a loss-of-function mutation in the TOMATO MADS-BOX 6 (TM6) gene is responsible for this mutant phenotype. Furthermore, as a result of the loss of function of TM6, misregulation of the transcription and mRNA processing of other MADS-box genes involved in reproductive development has been detected. Our findings demonstrate that TM6 is a key player in the complex regulatory network of MADS-box genes controlling flower development and also provide a novel mutant that may be useful for generating male sterile lines in tomatoes.

Transcription factors RhbZIP17 and RhWRKY30 enhance resistance to Botrytis cinerea by increasing lignin content in rose petals.

The petals of ornamental plants such as roses (Rosa spp.) are the most economically important organs. This delicate, short-lived plant tissue is highly susceptible to pathogens, in large part because the walls of petal cells are typically thinner and more flexible compared with leaf cells, allowing the petals to fold and bend without breaking. The cell wall is a dynamic structure that rapidly alters its composition in response to pathogen infection, thereby reinforcing its stability and boosting plant resistance against diseases. However, little is known about how dynamic changes in the cell wall contribute to resistance to Botrytis cinerea in rose petals. Here, we show that the B. cinerea-induced transcription factor RhbZIP17 is required for the defense response of rose petals. RhbZIP17 is associated with phenylpropanoid biosynthesis and binds to the promoter of the lignin biosynthesis gene RhCAD1, activating its expression. Lignin content showed a significant increase under gray mold infection compared with the control. RhCAD1 functions in the metabolic regulation of lignin production and, consequently, disease resistance, as revealed by transient silencing and overexpression in rose petals. The WRKY transcription factor RhWRKY30 is also required to activate RhCAD1 expression and enhance resistance against B. cinerea. We propose that RhbZIP17 and RhWRKY30 increase lignin biosynthesis, improve the resistance of rose petals to B. cinerea, and regulate RhCAD1 expression.

Cellulose assembles into helical bundles of uniform handedness in cell walls with abnormal pectin composition.

Plant cells and organs grow into a remarkable diversity of shapes, as directed by cell walls composed primarily of polysaccharides such as cellulose and multiple structurally distinct pectins. The properties of the cell wall that allow for precise control of morphogenesis are distinct from those of the individual polysaccharide components. For example, cellulose, the primary determinant of cell morphology, is a chiral macromolecule that can self-assemble in vitro into larger-scale structures of consistent chirality, and yet most plant cells do not display consistent chirality in their growth. One interesting exception is the Arabidopsis thaliana rhm1 mutant, which has decreased levels of the pectin rhamnogalacturonan-I and causes conical petal epidermal cells to grow with a left-handed helical twist. Here, we show that in rhm1 the cellulose is bundled into large macrofibrils, unlike the evenly distributed microfibrils of the wild type. This cellulose bundling becomes increasingly severe over time, consistent with cellulose being synthesized normally and then self-associating into macrofibrils. We also show that in the wild type, cellulose is oriented transversely, whereas in rhm1 mutants, the cellulose forms right-handed helices that can account for the helical morphology of the petal cells. Our results indicate that when the composition of pectin is altered, cellulose can form cellular-scale chiral structures in vivo, analogous to the helicoids formed in vitro by cellulose nano-crystals. We propose that an important emergent property of the interplay between rhamnogalacturonan-I and cellulose is to permit the assembly of nonbundled cellulose structures, providing plants flexibility to orient cellulose and direct morphogenesis.

Development of a protoplast isolation system for functional gene expression and characterization using petals of Camellia Oleifera

Protoplasts preparation and purification have been frequently used in plant genetics and breeding studies, whereas application of protoplasts in woody plants is still in its infancy. Although transient gene expression using purified protoplasts is well-documented and widely used in model plants and agriculture crops, no instance of either stable transformation or transient gene expression in the woody plant Camellia Oleifera has as of yet been reported. Here, we developed a protoplast preparation and purification method using C. oleifera petals by optimizing osmotic condition with D-mannitol and polysaccharide-degrading enzyme concentrations for petal cell wall digestion, to reach a high efficiency of protoplast productivity and viability. The achieved protoplasts yield was approximately 1.42 × 107 cells per gram of petal material and the viability of protoplasts was up to 89%. In addition, we explored influencing factors of protoplast transformation, including concentrations of PEG4000 and plasmid DNA. The transformation efficiency of 81% could be reached under the optimized condition. This protoplast isolation and transient expression system were deployed to further identify the functional regulation of C. oleifera related genes and the subcellular distribution of their encoded products. In summary, the protoplast isolation and transient expression system we established using oil-tea tree petals is an efficient, versatile and time-saving system, being suitable for gene function characterization and molecular mechanism analysis.

The swansong of petal cell death: insights into the mechanism and regulation of ethylene-mediated flower senescence.

Flower senescence is a fundamental aspect of the developmental trajectory in flowers, occurring after the differentiation of tissues and maturation of petals, and preceding the growth and development of seeds. It is accompanied by various alterations at the cytological, physiological, and molecular levels, similar to other forms of programmed cell death (PCD). It involves an intricate interplay of various plant growth regulators, with ethylene being the key orchestrator in ethylene-dependent petal senescence. Petal senescence mediated by ethylene is marked by various changes such as petal wilting, amplified oxidative stress, degradation of proteins and nucleic acids, and autophagy. Ethylene crosstalks with other growth regulators and triggers genetic and/or epigenetic reprogramming of genes during senescence in flowers. While our understanding of the mechanism and regulation of petal senescence in ethylene-sensitive species has advanced, significant knowledge gaps still exist, which demand critical reappraisal of the available literature on the topic. A deeper understanding of the various mechanisms and regulatory pathways involved in ethylene-dependent senescence has the capacity to facilitate a more precise regulation of the timing and site of senescence, thus leading to optimized crop yields, enhanced product quality, and extended longevity.

The ARF2-MYB6 module mediates auxin-regulated petal expansion in rose.

In cut rose (Rosa hybrida), the flower-opening process is closely associated with vase life. Auxin induces the expression of transcription factor genes that function in petal growth via cell expansion. However, the molecular mechanisms underlying the auxin effect during flower opening are not well understood. Here, we identified the auxin-inducible transcription factor gene RhMYB6, whose expression level is high during the early stages of flower opening. Silencing of RhMYB6 delayed flower opening by controlling petal cell expansion through down-regulation of cell expansion-related genes. Furthermore, we demonstrated that the auxin response factor RhARF2 directly interacts with the promoter of RhMYB6 and represses its transcription. Silencing of RhARF2 resulted in larger petal size and delayed petal movement. We also showed that the expression of genes related to ethylene and petal movement showed substantial differences in RhARF2-silenced petals. Our results indicate that auxin-regulated RhARF2 is a critical player that controls flower opening by governing RhMYB6 expression and mediating the crosstalk between auxin and ethylene signaling.

Functional identification of anthocyanin glucosyltransferase genes: a Ps3GT catalyzes pelargonidin to pelargonidin 3-O-glucoside painting the vivid red flower color of Paeonia.

Glycosylation from an anthocyanidin 3-O-glucosyltransferase Ps3GT (PsUGT78A27) facilitates the accumulation of pelargonidin 3-O-glucoside, which defines the vivid red flower color and occurs only in specific peony tree cultivars. Although tree peony cultivars of Chinese and Japanese both originated from China, vivid red color is only found in flowers of Japanese cultivars but not of Chinese cultivar groups. In this study, a Japanese tree peony cultivar 'Taiyoh' with vivid red petals and a Chinese tree peony cultivar 'Hu Hong' with reddish pink petals were chosen as the experimental materials. Flavonoids profiling indicated that pelargonidin 3-O-glucoside (Pg3G) detected only in Japanese cultivar contributed to vivid red color of tree peony petals, while pelargonidin 3,5-di-O-glucoside (Pg3G5G) found in both of Japanese and Chinese cultivars was responsible for pink flower color. Through the integration of full-length transcriptome sequencing and in vitro enzymatic activity analysis, two anthocyanin glucosyltransferase genes PsUGT78A27 and PsUGT75L45 were isolated from the petals of tree peony, and their encoding products exhibited enzymatic activities of pelargonidin 3-O-glucosyltransferase and anthocyanin 5-O-glucosyltransferase, respectively. Further quantitative real-time PCR revealed that PsUGT78A27 displayed high expression in petals of both cultivars and PsUGT75L45 was expressed at high levels in cultivar 'Hu Hong' only. Using a gene gun technique, the GFP fusion proteins of PsUGT78A27 and PsUGT75L45 were visualized to be cytoplasmic and nuclear localization in the epidermal cells of tree peony petals, and the glucosylation function of PsUGT78A27 and PsUGT75L45 to alter petal color of tree peony and herbaceous peony had been directly validated in vivo. These results demonstrated that PsUGT78A27 and PsUGT75L45 are key players for the presence or absence of vivid red flower color in tree peony cultivars. Our findings further elucidated the chemical and molecular mechanism of petal pigmentation of Paeonia and could help breed the Paeonia cultivars possessing novel flower colors.

Study on the frequency of ultraviolet (UV) light reflectance and absorption in native and nonnative flowering plants

In addition to the floral shape and colors seen by the human eye, ultraviolet (UV) reflectance serves as a significant visual advertisement for pollinators of many blooming plant species. The interaction between flowers and pollinators is significantly influenced by plant UV patterns. It is common knowledge that many flowers have vacuolated pigments that are UV-absorbing in their petal cells. Nevertheless, the impact of UV reflection and absorption on pollinators to particular plant species hasn't been properly investigated. In this paper, the degree and pattern of UV light reflection in flowers of 240 plant species from 55 families were examined. Four levels of UV absorption and reflection were used to rank the flowers. While white and green flowers often reflect UV weakly, yellow and violet flowers have the highest likelihood of doing so. In general, pollination aids were nonreflective and independent of hue. UV reflection seems to be positively connected with flower size even though it is unrelated to floral symmetry. UV reflection is certainly present in all plant families; however, it seems to be more prevalent in some taxonomic groups. UV reflection and absorption appear to be influenced by the physical features and chemical make-up of the petals, just like other floral petals.

Plant-cell oriented few-layer MoS2/C as high performance anodes for lithium-ion batteries

MoS 2 with layered structure and high theoretical capacity (670 mAh· g − 1 ) has attracted great attention as a potential anode material for lithium-ion batteries (LIBs). However, the intrinsic low electronic conductivity and structural collapse during the lithiation/delithiation process hinder its practical application. In this study, a few-layer MoS 2 decorated biocarbon (MoS 2 /C) was exquisitely constructed employing petal cells as structure-directing agents. In the synthesis process, nucleation and growth of MoS 2 were restricted in the confined space of petal cells, and thus MoS 2 nanosheets (about 3–8 layers) grew vertically and dispersed uniformly on the petal-cell derived biocarbon matrix. The special structure effectively alleviates volume expansion and restack of MoS 2 during the lithiation/delithiation process, while the in situ generated biocarbon improves the conductivity of electrode, thus boosting electron transportation and Li + diffusivity. Moreover, theoretical calculations reveal the lower Li + migration barrier energies and improved Li + diffusion kinetics in MoS 2 /C hetero-layer. Consequently, the MoS 2 /C exhibits remarkable rate performance and cycle stability, showing a superior reversible capacity (951 mAh· g − 1 over 500 cycles at 100 mA· g − 1 ) much larger than bulk MoS 2 (108 mAh· g − 1 ) and biocarbon (355 mAh· g − 1 ). This study provides a convenient and effective strategy to design advanced electrodes for the next-generation energy storage and conversion systems.

The diversity of elaborate petals in Isopyreae (Ranunculaceae): a special focus on nectary structure.

Elaborate petals are highly diverse in morphology, structure, and epidermal differentiation and play a key role in attracting pollinators. There have been few studies on the elaborate structure of petals in the tribe Isopyreae (Ranunculaceae). Seven genera in Isopyreae (Aquilegia, Semiaquilegia, Urophysa, Isopyrum, Paraquilegia, Dichocarpum, and Leptopyrum) have petals that vary in morphology, and two genera (Enemion and Thalictrum) have no petals. The petals of nine species belonged to 7 genera in the tribe were studied to reveal their nectary structure, epidermal micromorphology and ancestral traits. The petal nectaries of Isopyreae examined in this study were located at the tip of spurs (Aquilegia yabeana and A. rockii), or the bottom of shallow sacs (Semiaquilegia adoxoides, Urophysa henryi, Isopyrum manshuricum, and Paraquilegia microphylla), a cup-shaped structure (Dichocarpum fargesii) and a bilabiate structure (Leptopyrum fumarioides). The petal nectary of eight species in Isopyreae (except A. ecalcarata) was composed of secretory epidermis, nectary parenchyma, and vascular tissues, and some sieve tubes reached the secretory parenchyma cells. Among the eight species with nectaries examined in the present study, A. yabeana had the most developed nectaries, with 10-15 layers of secretory parenchyma cells. The epidermal cells of mature petals of the nine species were divided into 11 types. Among these 11 types, there were two types of secretory cells and two types of trichomes. Aquilegia yabeana and A. rockii had the highest number of cell types (eight types), and I. manshuricum and L. fumarioides had the lowest number of cell types (three types). Aquilegia ecalcarata had no secretory cells, and the papillose conical polygonal secretory cells of D. fargesii were different from those of the other seven species with nectaries. Trichomes were found only in Aquilegia, Semiaquilegia, Urophysa, and Paraquilegia. The ancestral mode of nectar presentation in Isopyreae was petals with hidden nectar (70.58%). The different modes of nectar presentation in petals may reflect adaptations to different pollinators in Isopyreae.

Overexpression of Rice BSR2 Confers Disease Resistance and Induces Enlarged Flowers in Torenia fournieri Lind

Plant pathogens evade basal defense systems and attack different organs and tissues of plants. Genetic engineering of plants with genes that confer resistance against pathogens is very effective in pathogen control. Conventional breeding for disease resistance in ornamental crops is difficult and lagging relative to that in non-ornamental crops due to an inadequate number of disease-resistant genes. Therefore, genetic engineering of these plants with defense-conferring genes is a practical approach. We used rice BSR2 encoding CYP78A15 for developing transgenic Torenia fournieri Lind. lines. The overexpression of BSR2 conferred resistance against two devastating fungal pathogens, Rhizoctonia solani and Botrytis cinerea. In addition, BSR2 overexpression resulted in enlarged flowers with enlarged floral organs. Histological observation of the petal cells suggested that the enlargement in the floral organs could be due to the elongation and expansion of the cells. Therefore, the overexpression of BSR2 confers broad-spectrum disease resistance and induces the production of enlarged flowers simultaneously. Therefore, this could be an effective strategy for developing ornamental crops that are disease-resistant and economically more valuable.

An anatomical comparison of epidermal cells in wild-type and homeotic mutant flowers of Clarkia tembloriensis Vasek (Onagraceae) 1

Flowers consist of four whorls of organs (sepals, petals, stamens, and carpels), each expressing unique characteristics. In floral homeotic mutants, organs develop abnormally, and floral organs of one whorl express characteristics of another whorl. Much of our current understanding of the development of floral organs has been based on studies of floral homeotic mutants. In the homeotic mutant crinkle-petal (cp) of Clarkia tembloriensis, previous investigations demonstrated that the cp petal is a hybrid organ combining characteristics of sepals and petals. This investigation extends those studies with a comparative anatomical study of trichomes, guard cells, and marginal epidermal cells in wild-type (WT) sepals, WT petals, and cp petals. The aim was to determine if cp petals exhibit a hybrid epidermal anatomy of WT sepals and WT petals. Floral buds 1 day pre-anthesis and flowers 1 day post-anthesis were collected and prepared for light microscopy or scanning electron microscopy. Trichomes and guard cell pairs were described and counted, and marginal cells were observed and described. This anatomical study of trichomes, guard cells, and marginal cells demonstrated that cp petals of C. tembloriensis combine characteristics of both WT sepals and WT petals. These results provide further support for the hybrid nature of cp petals in Clarkia tembloriensis.

Ectopic Expression of Poplar PsnCYCD1;1 Reduces Cell Size and Regulates Flower Organ Development in Nicotiana tabacum.

The D-type cyclin (CYCD) gene, as the rate-limiting enzyme in the G1 phase of cell cycle, plays a vital role in the process of plant growth and development. Early studies on plant cyclin mostly focused on herbs, such as Arabidopsis thaliana. The sustainable growth ability of woody plants is a unique characteristic in the study of plant cyclin. Here, the promoter of PsnCYCD1;1 was cloned from poplar by PCR and genetically transformed into tobacco. A strong GUS activity was observed in the areas with vigorous cell division, such as stem tips, lateral buds, and young leaves. The PsnCYCD1;1-GFP fusion expression vector was transformed into tobacco, and the green fluorescence signal was observed in the nucleus. Compared with the control plant, the transgenic tobacco showed significant changes in the flower organs, such as enlargement of sepals, petals, and fruits. Furthermore, the stems of transgenic plants were slightly curved at each stem node, the leaves were curled on the adaxial side, and the fruits were seriously aborted after artificial pollination. Microscopic observation showed that the epidermal cells of petals, leaves, and seed coats of transgenic plants became smaller. The transcriptional levels of endogenous genes, such as NtCYCDs, NtSTM, NtKNAT1, and NtASs, were upregulated by PsnCYCD1;1. Therefore, PsnCYCD1;1 gene played an important role in the regulation of flower organ and stem development, providing new understanding for the functional characterization of CYCD gene and new resources for improving the ornamental value of horticultural plants.