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Clay J. Carter - One of the best experts on this subject based on the ideXlab platform.
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a cell wall invertase controls nectar volume and sugar composition
Plant Journal, 2021Co-Authors: Anzu Minami, Xiaojun Kang, Clay J. CarterAbstract:Nectar volume and sugar composition are key determinants in the strength of plant-pollinator mutualisms. The main nectar sugars are sucrose, glucose, and fructose, which can vary widely in ratio and concentration across species. Brassica spp. produce a hexose-dominant nectar (high in the monosaccharides glucose and fructose) with very low levels of the disaccharide sucrose. Cell wall invertases (CWINVs) catalyze the irreversible hydrolysis of sucrose into glucose and fructose in the apoplast. We found that BrCWINV4A is highly expressed in the nectaries of Brassica rapa. Moreover, a brcwinv4a null mutant has (1) greatly reduced cell wall invertase activity in the nectaries, and (2) produces a sucrose-rich nectar, but (3) with significantly less volume. These results definitively demonstrate that CWINV activity is not only essential for the production of a hexose-rich nectar, but also support a hypothetical model of nectar secretion in which its hydrolase activity is required for maintaining a high intracellular-to-extracellular sucrose ratio that facilitates the continuous export of sucrose into the Nectary apoplast. Extracellular hydrolysis of each sucrose into two hexoses by BrCWINV4A also likely creates the osmotic potential required for nectar droplet formation. These results cumulatively indicate that modulation of CWINV activity can at least partially account for naturally occurring differences in nectar volume and sugar composition. Lastly, honey bees prefer nectars with some sucrose, but wild-type B. rapa flowers were much more heavily visited than those of brcwinv4a, suggesting that the potentially attractive sucrose-rich nectar of brcwinv4a could not compensate for its low volume.
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the role of alanine synthesis and nitrate induced nitric oxide production during hypoxia stress in cucurbita pepo nectaries
Plant Journal, 2021Co-Authors: Erik M Solhaug, Rahul Roy, Rodney T Venterea, Clay J. CarterAbstract:Floral nectar is a sugary solution produced by nectaries to attract and reward pollinators. Nectar metabolites, such as sugars, are synthesized within the Nectary during secretion from both pre-stored and direct phloem-derived precursors. In addition to sugars, nectars contain nitrogenous compounds such as amino acids; however, little is known about the role(s) of nitrogen (N) compounds in Nectary function. In this study, we investigated N metabolism in Cucurbita pepo (squash) floral nectaries in order to understand how various N-containing compounds are produced and determine the role of N metabolism in nectar secretion. The expression and activity of key enzymes involved in primary N assimilation, including nitrate reductase (NR) and alanine aminotransferase (AlaAT), were induced during secretion in C. pepo nectaries. Alanine (Ala) accumulated to about 35% of total amino acids in nectaries and nectar during peak secretion; however, alteration of vascular nitrate supply had no impact on Ala accumulation during secretion, suggesting that nectar(y) amino acids are produced by precursors other than nitrate. In addition, nitric oxide (NO) is produced from nitrate and nitrite, at least partially by NR, in nectaries and nectar. Hypoxia-related processes are induced in nectaries during secretion, including lactic acid and ethanolic fermentation. Finally, treatments that alter nitrate supply affect levels of hypoxic metabolites, nectar volume and nectar sugar composition. The induction of N metabolism in C. pepo nectaries thus plays an important role in the synthesis and secretion of nectar sugar.
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systems analyses of key metabolic modules of floral and extrafloral nectaries of cotton
bioRxiv, 2019Co-Authors: Elizabeth C Chatt, Clay J. Carter, Marshall Hampton, Peter M Klinkenberg, Sitinabilla Mahalim, Nuraziatull Mohdfadzil, Rahul Roy, Harry T Horner, Basil J. NikolauAbstract:Abstract Nectar is a primary reward mediating plant-animal mutualisms to improve plant fitness and reproductive success. In Gossypium hirsutum (cotton), four distinct trichomatic nectaries develop, one floral and three extrafloral. The secreted floral and extrafloral nectars serve different purposes, with the floral nectar attracting bees to promote pollination and the extrafloral nectar attracting predatory insects as a means of indirect resistance from herbivores. Cotton therefore provides an ideal system to contrast mechanisms of nectar production and nectar composition between floral and extrafloral nectaries. Here, we report the transcriptome, ultrastructure, and metabolite spatial distribution using mass spectrometric imaging of the four cotton Nectary types throughout development. Additionally, the secreted nectar metabolomes were defined and were jointly composed of 197 analytes, 60 of which were identified. Integration of theses datasets support the coordination of merocrine-based and eccrine-based models of nectar synthesis. The Nectary ultrastructure supports the merocrine-based model due to the abundance of rough endoplasmic reticulum positioned parallel to the cell walls and profusion of vesicles fusing to the plasma membranes. The eccrine-based model which consist of a progression from starch synthesis to starch degradation and to sucrose biosynthesis was supported by gene expression data. This demonstrates conservation of the eccrine-based model for the first time in both trichomatic and extrafloral nectaries. Lastly, Nectary gene expression data provided evidence to support de novo synthesis of amino acids detected in the secreted nectars. One sentence summary The eccrine-based model of nectar synthesis and secretion is conserved in both trichomatic and extrafloral nectaries determined by a system-based comparison of cotton (Gossypium hirsutum) nectaries.
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carbohydrate metabolism and signaling in squash nectaries and nectar throughout floral maturation
Plant Physiology, 2019Co-Authors: Erik M Solhaug, Elizabeth M Johnson, Clay J. CarterAbstract:Floral nectar is a sugary solution produced by plants to entice pollinator visitation. A general mechanism for nectar secretion has been established from genetic studies in Arabidopsis (Arabidopsis thaliana); however, supporting metabolic and biochemical evidence for this model is scarce in other plant species. We used squash (Cucurbita pepo) to test whether the genetic model of nectar secretion in Arabidopsis is supported at the metabolic level in other species. As such, we analyzed the expression and activity of key enzymes involved in carbohydrate metabolism in squash nectaries throughout floral maturation and the associated starch and soluble sugars, as well as nectar volume and sugar under different growth conditions. Here we show that the steps that are important for nectar secretion in Arabidopsis, including Nectary starch degradation, Suc synthesis, and Suc export, are supported by metabolic and biochemical data in C. pepo. Additionally, our findings suggest that sugars imported from the phloem during nectar secretion, without prior storage as starch, are important for generating C. pepo nectar. Finally, we predict that trehalose and trehalose 6-P play important regulatory roles in Nectary starch degradation and nectar secretion. These data improve our understanding of how nectar is produced in an agronomically relevant species with the potential for use as a model to help us gain insight into the biochemistry and metabolism of nectar secretion in flowering plants.
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an integrated transcriptomics and metabolomics analysis of the cucurbita pepo Nectary implicates key modules of primary metabolism involved in nectar synthesis and secretion
Plant direct, 2019Co-Authors: Erik M Solhaug, Marshall Hampton, Peter M Klinkenberg, Basil J. Nikolau, Elizabeth C Chatt, Nuraziatull Mohdfadzil, Rahul Roy, Clay J. CarterAbstract:Nectar is the main reward that flowers offer to pollinators to entice repeated visitation. Cucurbita pepo (squash) is an excellent model for studying nectar biology, as it has large nectaries that produce large volumes of nectar relative to most other species. Squash is also monoecious, having both female and male flowers on the same plant, which allows comparative analyses of Nectary function in one individual. Here, we report the Nectary transcriptomes from both female and male nectaries at four stages of floral maturation. Analysis of these transcriptomes and subsequent confirmatory experiments revealed a metabolic progression in nectaries leading from starch synthesis to starch degradation and to sucrose biosynthesis. These results are consistent with previously published models of nectar secretion and also suggest how a sucrose-rich nectar can be synthesized and secreted in the absence of active transport across the plasma membrane. Nontargeted metabolomic analyses of nectars also confidently identified 40 metabolites in both female and male nectars, with some displaying preferential accumulation in nectar of either male or female flowers. Cumulatively, this study identified gene targets for reverse genetics approaches to study Nectary function, as well as previously unreported nectar metabolites that may function in plant-biotic interactions.
Leonardo Galetto - One of the best experts on this subject based on the ideXlab platform.
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anatomy of the floral Nectary of ornithophilous elleanthus brasiliensis orchidaceae sobralieae
Botanical Journal of the Linnean Society, 2013Co-Authors: Carlos Eduardo Pereira Nunes, Leonardo Galetto, Marilia De Moraes Castro, Marlies SazimaAbstract:Orchidaceae show enormous floral diversity. However, anatomical studies of Nectary tissues relative to nectar composition and pollinators are scarce. This work aims to present a detailed anatomical study of the labellar Nectary of Elleanthus brasiliensis, analyse the chemical composition of its nectar and relate these findings to pollination biology. Basally, the labellum bears a pair of fleshy, whitish, ovoid calli on its adaxial surface. Nectariferous callus tissue consists of a papillate epidermis and enlarged subepidermal parenchyma cells with thin walls, large nuclei and dense cytoplasm which stained positively for hydrophilic substances, interpreted as pre-nectar. The paired calli lack vascular tissues, but at the point of callus insertion, the diameters of vascular bundles supplying the lip are larger. Nectar is secreted as droplets on the adaxial callus surface. It is produced in small quantities, c. 4 μL per flower. Callus cell contents tested negative for polysaccharides, lipids and phenolic compounds. The nectar is sucrose-dominant, as in other hummingbird-pollinated species. It is suggested that other ornithophilous species of Sobralieae have anatomically similar nectaries. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 171, 764–772.
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four o clock pollination biology nectaries nectar and flower visitors in nyctaginaceae from southern south america
Botanical Journal of the Linnean Society, 2013Co-Authors: María J. Nores, Hernán A. López, Ana M. Anton, Paula J Rudall, Leonardo GalettoAbstract:Floral Nectary structure and nectar sugar composition were investigated in relation to other floral traits and flower visitors in contrasting species of Nyctaginaceae from southern South America, representing four tribes (Bougainvilleeae, Colignonieae, Nyctagineae, Pisoneae). Our comparative data will aid in the understanding of plant–pollinator interactions and in the development of hypotheses on the origin of floral and reproductive characters in this family. The nectaries are located on the inner side of the staminal tube. The nectariferous tissue is composed of an epidermis and three to ten layers of secretory parenchymal cells, supplied indirectly by the filament vascular bundles. Stomata appear to be associated with nectar secretion. For the first time in Nyctaginaceae, Nectary ultrastructure is described in Boerhavia diffusa var. leiocarpa. Nectary parenchyma cells are densely cytoplasmic and contain numerous starch grains. Plasmodesmata connect the nectariferous cells. Flowers of Nyctaginaceae secrete a small volume of nectar of variable concentration (10–47%). Nectar is dominated by hexoses, but Mirabilis jalapa showed a balanced proportion of sucrose and hexoses. Hymenoptera are the most common visitors for most species; nocturnal Lepidoptera are the most common visitors for M. jalapa and Bougainvillea stipitata. We found relatively low variation in the Nectary characteristics of Nyctaginaceae compared with broad variation in flower structure, shape, colour and nectar traits. © 2013 The Linnean Society of London
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floral nectaries nectar production dynamics and chemical composition in six ipomoea species convolvulaceae in relation to pollinators
Annals of Botany, 2004Co-Authors: Leonardo Galetto, Gabriel BernardelloAbstract:Background and Aims Floral nectaries and nectar features were compared between six Argentinian Ipomoea species with differences in their pollinator guilds: I. alba, I. rubriflora, I. cairica, I. hieronymi var. hieronymi, I. indica, and I. purpurea. Methods Pollinators were recorded in natural populations. The morpho-anatomical study was carried out through scanning electron and light microscopy. Nectar sugars were identified via gas chromatography. Nectar production and the effect of its removal on total nectar sugar amount were determined by using sets of bagged flowers. Key Results Hymenopterans were visitors of most species, while hummingbirds visited I. rubriflora and sphingids I. alba. All the species had a vascularized discoidal Nectary surrounding the ovary base with numerous open stomata with a species-specific distribution. All nectar samples contained amino acids and sugars. Most species had sucrosedominant nectars. Flowers lasted a few hours. Mean nectar sugar concentration throughout the lifetime of the flower ranged from 3428 to 3942 %, except for I. cairica (4925 %) and I. rubriflora (2518 %). Ipomoea alba had the highest nectar volume secreted per flower (5012 mL), while in the other taxa it ranged from 242 to 1200 mL. Nectar secretion began as soon as the flowers opened and lasted for a few hours (in I. purpurea, I. rubriflora) or it was continuous during the lifetime of the flower (in the remaining species). There was an increase of total sugar production after removals in I. cairica, I. indica and I. purpurea, whereas in I. alba and I. rubriflora removals had no effect, and in I. hieronymi there was a decrease in total sugar production. Conclusions The chemical composition, production dynamics and removal effects of nectar could not be related to the pollinator guild of these species. Flower length was correlated with Nectary size and total volume of nectar secreted, suggesting that structural constraints may play a major role in the determination of nectar traits of these species. a 2004 Annals of Botany Company
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floral Nectary structure and nectar chemical composition of some species from robinson crusoe island chile
Botany, 2000Co-Authors: Gabriel Bernardello, Leonardo Galetto, Gregory J AndersonAbstract:Floral Nectary structure and nectar composition of 12 species, including 11 endemics, are reported from Robinson Crusoe Island (Juan Fernandez Archipelago, Chile). These species are mostly hummingbird pollinated. Nectary morphology follows the general pattern within each of the families, suggesting it is an ancestral feature. The mean nectar concentration (± SD) as a percentage of weight (weight/total weight of solution) was 28.3 ± 20.7. Sucrose, fructose, and glucose were identified in most samples. In Nicotiana cordifolia, an unknown monosaccharide was also detected. When more than one sample per species was examined, there was usually variability in sugar ratios. Statistical tests indicated that population size does not influence this variability. However, there were differences when the pollinator type was compared, with a trend of a higher sucrose proportion and a lower coefficient of variation of sucrose in the species pollinated by hummingbirds. This would indicate a specialization in the nectar co...
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nectar nectaries flower visitors and breeding system in five terrestrial orchidaceae from central argentina
Journal of Plant Research, 1997Co-Authors: Leonardo Galetto, Gabriel Bernardello, Guillermo L RiveraAbstract:Floral nectar sugar composition, Nectary anatomy, and visitors are studied in five Argentine Orchidaceae, from 18 populations. Hand-pollinations were performed to evaluate their breeding system. We found two different types of perigonal nectaries located either in the spur (Habenaria gouriieana, H. hieronymi, Habenariinae), or in the basal lateral parts of the labellum (Beadlea dutraei, Pelexia bonariensis, Stenorrhynchos orchioides, Spiranthinae). The spur ofHabenaria is a nonvascularised and nonstructural Nectary. The inner epidermis bears one-celled long papillae. In bud stage, the papillae are filled with starch grains, but when the flower opens and nectar secretion starts, they show no starch grains. This fact may indicate that starch is a source for some of the secreted nectar. In the remainder genera, the lateral basal parts of the labellum are secretory. The two glands are located in the adaxial basal lateral faces of the labellum. These nectaries are structural and nonvascularised.Stenorrhynchos produces abundant, concentrated nectar (40–50%).Habenaria gourlieana accumulates copious nectar in a lower concentration (<20%), whereas the other species produce small quantities of concentrated nectar (ca. 50%). Three of the studied species have sucrose predominant nectar (Beadlea dutrael, Habenaria gourlieana, andPelexia bonariensis) whileH. hieronymi, Stenorrhynchos orchioides have hexose predominant ones. Nectar removal and/or pollination induce flower senescence.H. gouriieana is visited by sphingids,S. orchioides by hummingbirds, andB. dutrael by bees. For the two other species we did not record flower visitors.Pelexia bonariensis, B. dutrael, andS. orchiodes are self-compatible species but a pollinator is needed.
Arthur R Davis - One of the best experts on this subject based on the ideXlab platform.
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annular floral Nectary with oil producing trichomes in salvia farinacea lamiaceae anatomy histochemistry ultrastructure and significance
American Journal of Botany, 2014Co-Authors: Xiaohui Zhang, V K Sawhney, Arthur R DavisAbstract: Premise of the study: Many angiosperms produce nectar that entices pollinator visits. Each fl oral Nectary tends to embody a singular form, such as the receptacular ring arising beneath the ovary in mint fl owers (Lamiaceae). Exceptionally, the annular fl oral Nectary in Salvia farinacea possesses modifi ed stomata plus secretory trichomes. This fi rst study of Nectary ultrastructure within the largest genus of Lamiaceae examined this unusual condition. Methods: Nectary anatomy, histochemistry, and ultrastructure were investigated from fresh and fi xed material using light microscopy and scanning electron and transmission electron microscopy. Key results: The annular Nectary encircled the ovary plus extended ventrally as a projection. Modifi ed stomata occurred only in the projection’s abaxial epidermis. Conversely, peltate trichomes with a basal cell, a stalk cell, and 4-7 head cells were interspersed among the ovary lobes and covered the projection’s adaxial surface. Phloem and xylem supplied the Nectary interior, where parenchyma cells had numerous mitochondria and plastids with little starch, but few dictyosomes and little endoplasmic reticulum. Nectar accumulated as a drop opposite the projection’s abaxial surface, escaping through stomatal pores and probably the cuticle. However, the annular Nectary’s glistening trichomes secreted a Sudan-positive product largely retained below the distended cuticle, but not nectar. Conclusions: This fi rst ultrastructural study of co-occurring secretory trichomes and modifi ed stomata on a mint Nectary suggests multiple interactive functions for this atypical structure. These trichomes—possibly generating a substance informative to pollinators or as an ovarian defense against phytophagy—produced oil in an aqueous milieu, rather than contributing fl uid to nectar.
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floral Nectary structure nectar production and carbohydrate composition in the lilium asiatic hybrid tresor
Botany, 2010Co-Authors: Jessica Stolarj Stolar, Arthur R DavisAbstract:Floral Nectary structure, nectar production, and carbohydrate composition were compared from petals (“inner tepals”) and sepals (“outer tepals”) of Lilium Asiatic hybrid ‘Tresor’ (Liliaceae). The s...
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floral structure and dynamics of nectar production in echinacea pallida var angustifolia asteraceae
International Journal of Plant Sciences, 2008Co-Authors: Tyler J Wist, Arthur R DavisAbstract:The reproductive structure of the disk florets of Echinacea pallida var. angustifolia (Asteraceae) in relation to insect pollination was investigated using light, fluorescence, and scanning electron microscopy. The study of this self‐incompatible species emphasized pollen production, pollen‐stigma interactions, transmitting tissue, and vasculature within the style. Nectary structure and nectar production dynamics were also examined. Produced in the fused anther tubes, the trinucleate pollen with yellow pollenkitt was plentiful per floret, yielding a pollen:ovule ratio of 24,130. Encircling the style base at the ovary summit, the floral Nectary possessed modified stomata whose pores, as well as nonstomatal gaps in the epidermis, provided apoplastic pathways for nectar escape and reabsorption. Phloem alone supplied the gland interior, the sieve element–companion cell complexes reaching up to the Nectary epidermis. Nectar was hexose dominant, its volume and nectar‐sugar quantity per floret peaking on the aft...
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floral nectar production and Nectary anatomy and ultrastructure of echinacea purpurea asteraceae
Annals of Botany, 2006Co-Authors: Tyler J Wist, Arthur R DavisAbstract:• Background and Aims In spite of the impressive species diversity in the Asteraceae and their widespread appeal to many generalist pollinators, floral-Nectary ultrastructure in the family has rarely been investigated. To redress this, a study using Echinacea purpurea, a plant of horticultural and nutraceutical value, was undertaken. Nectar secretion of disc florets was compared with floral Nectary ultrastructure taking into account nectar's potential impact upon the reproductive success of this outcrossing species. • Methods Micropipette collections of nectar in conjunction with refractometry were used to determine the volume and nectar-sugar quantities of disc florets throughout their phenology, from commencement of its production to cessation of secretion. Light, scanning-electron and transmission-electron microscopy were utilized to examine morphology, anatomy and ultrastructure of nectaries of the disc florets. • Key Results Florets were protandrous with nectar being secreted from anthesis until the third day of the pistillate phase. Nectar production per floret peaked on the first day of stigma receptivity, making the two innermost whorls of open florets most attractive to foraging visitors. Modified stomata were situated along the apical rim of the collar-like Nectary, which surrounds the style base and sits on top of the inferior ovary. The floral Nectary was supplied by phloem only, and both sieve elements and companion cells were found adjacent to the epidermis; the latter participated in the origin of some of the precursor cells that yielded these specialized cells of phloem. Companion cells possessed wall ingrowths (transfer cells). Lobed nuclei were a key feature of secretory parenchyma cells. • Conclusions The abundance of mitochondria suggests an eccrine mechanism of secretion, although dictyosomal vesicles may contribute to a granulocrine process. Phloem sap evidently is the main contributor of nectar carbohydrates. From the sieve elements and companion cells, an apoplastic route via intercellular spaces and cell walls, leading to the pores of modified stomata, is available. A symplastic pathway, via plasmodesmata connecting sieve elements to companion, parenchyma and epidermal cells, is also feasible. Uncollected nectar was reabsorbed, and the direct innervation of the Nectary by sieve tubes potentially serves a second important route for nectar-sugar reclamation. Microchannels in the outer cuticle may facilitate both secretion and reabsorption.
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anatomical and ultrastructural changes of the floral Nectary ofpisum sativum l during flower development
Protoplasma, 1999Co-Authors: Fawzi A Razem, Arthur R DavisAbstract:The floral Nectary ofPisum sativum L. is situated on the receptacle at the base of the gynoecium. The gland receives phloem alone which departed the vascular bundles supplying the staminal column. Throughout the Nectary, only the companion cells of the phloem exhibited wall ingrowths typical of transfer cells. Modified stomata on the Nectary surface served as exits for nectar, but stomatal pores developed well before the commencement of secretion. Furthermore, stomatal pores on the Nectary usually closed by occlusion, not by guard-cell movements. Pore occlusion was detected most frequently in post-secretory and secretory glands, and less commonly in pre-secretory nectaries. A quantitative stereological study revealed few changes in Nectary fine structure between buds, flowers secreting nectar, and post-secretory flowers. Dissolution of abundant starch grains in plastids of subepidermal secretory cells when secretion commenced suggests that starch is a precursor of nectar carbohydrate production. Throughout Nectary development, mitochondria were consistently the most plentiful organelle in both epidermal and subepidermal cells, and in addition to the relative paucity of dictyosomes, endoplasmic reticulum, and their associated vesicles, the evidence suggests that floral nectar secretion inP. sativum is an energy-requiring (eccrine) process, rather that granulocrine.
Robert W Thornburg - One of the best experts on this subject based on the ideXlab platform.
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metabolomic profiling of nicotiana spp nectars indicate that pollinator feeding preference is a stronger determinant than plant phylogenetics in shaping nectar diversity
Metabolites, 2020Co-Authors: Fredy A Silva, Basil J. Nikolau, Elizabeth C Chatt, Sitinabilla Mahalim, Adel Guirgis, Xingche Guo, Dan Nettleton, Robert W ThornburgAbstract:Floral nectar is a rich secretion produced by the Nectary gland and is offered as reward to attract pollinators leading to improved seed set. Nectars are composed of a complex mixture of sugars, amino acids, proteins, vitamins, lipids, organic and inorganic acids. This composition is influenced by several factors, including floral morphology, mechanism of nectar secretion, time of flowering, and visitation by pollinators. The objective of this study was to determine the contributions of flowering time, plant phylogeny, and pollinator selection on nectar composition in Nicotiana. The main classes of nectar metabolites (sugars and amino acids) were quantified using gas chromatography/mass spectrometric analytical platforms to identify differences among fifteen Nicotiana species representing day- and night-flowering plants from ten sections of the genus that are visited by five different primary pollinators. The nectar metabolomes of different Nicotiana species can predict the feeding preferences of the target pollinator(s) of each species, and the nectar sugars (i.e., glucose, fructose, and sucrose) are a distinguishing feature of Nicotiana species phylogeny. Moreover, comparative statistical analysis indicate that pollinators are a stronger determinant of nectar composition than plant phylogeny.
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knockdown of myb305 disrupts Nectary starch metabolism and floral nectar production
Plant Journal, 2012Co-Authors: Guangyu Liu, Robert W ThornburgAbstract:MYB transcription factors have important roles during floral organ development. In this study, we generated myb305 RNAi knockdown tobacco plants and studied the role of MYB305 in the growth of the floral Nectary. We have previously shown the MYB305 regulates the expression of flavonoid metabolic genes as well as of nectar proteins (nectarins); however, the myb305 plants showed other floral phenotypes that we investigate in these studies. The nectaries of myb305 plants show juvenile character at late stages of development and secrete reduced levels of nectar. Because starch metabolism is intimately involved in nectar secretion and is strongly regulated during normal Nectary development, we examined the accumulation of starch in the nectaries of the myb305 plants. The myb305 plants accumulated lower levels of starch in their nectaries than did wild-type plants. The reduced starch correlated with the reduced expression of the ATP-glucose pyrophosphorylase (small subunit) gene in nectaries of the myb305 plants during the starch biosynthetic phase. Expression of genes encoding several starch-degrading enzymes including β-amylase, isoamylase 3, and α-amylase was also reduced in the myb305 plants. In addition to regulating nectarin and flavonoid metabolic gene expression, these results suggest that MYB305 may also function in the tobacco Nectary maturation program by controlling the expression of starch metabolic genes.
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transient starch metabolism in ornamental tobacco floral nectaries regulates nectar composition and release
Plant Science, 2007Co-Authors: Gang Ren, Harry T Horner, Rosanne A Healy, Anna M Klyne, Martha G James, Robert W ThornburgAbstract:Enlargement of the floral Nectary gland of ornamental tobacco during its development is accompanied by a major accumulation of starch granules in Nectary amyloplasts. Quantification of starch in the Nectary at various developmental stages showed little starch accumulation at early stages but increasing amounts of starch over the course of Nectary development that reached a peak approximately 24 h prior to anthesis. After this point, the amount of starch declined dramatically, suggesting its conversion to sugars (sucrose, glucose, and fructose) for the nectar production that occurs at anthesis. Compositional and structural analyses of Nectary starch showed that amylose content and degree of amylopectin branching also varied during Nectary development. Increasingly complex starch structures were observed up to intermediate stages of Nectary development, followed by decreased starch complexity and amount in the mature Nectary. Although the total amount of carbohydrate stored in the Nectary at mid-development is roughly equivalent to the carbohydrate in nectar sugars at anthesis, four- to five-times more sugar is secreted into nectar following anthesis. Radiolabeling of sugars prior to their transport into the flower bud, Nectary, and nectar showed the flow of sugars into the Nectary increased markedly after anthesis. The finding that the Nectary is the strongest sink tissue of all floral organs suggests that two processes, starch degradation and rapid sugar influx, are determinants of sugar composition in floral nectar. A model is presented in which these two processes are coordinated for high-level nectar production and release.
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tobacco nectaries express a novel nadph oxidase implicated in the defense of floral reproductive tissues against microorganisms
Plant Physiology, 2006Co-Authors: Clay J. Carter, Harry T Horner, Gang Ren, Rosanne A Healy, Nicole M Otool, S Saqlan M Naqvi, Sanggyu Park, Gwyn A Beattie, Robert W ThornburgAbstract:Hydrogen peroxide produced from the nectar redox cycle was shown to be a major factor contributing to inhibition of most microbial growth in floral nectar; however, this obstacle can be overcome by the floral pathogen Erwinia amylovora. To identify the source of superoxide that leads to hydrogen peroxide accumulation in Nectary tissues, nectaries were stained with nitroblue tetrazolium. Superoxide production was localized near Nectary pores and inhibited by diphenylene iodonium but not by cyanide or azide, suggesting that NAD(P)H oxidase is the source of superoxide. Native PAGE assays demonstrated that NADPH (not NADH) was capable of driving the production of superoxide, diphenyleneiodonium chloride was an efficient inhibitor of this activity, but cyanide and azide did not inhibit. These results confirm that the production of superoxide was due to an NADPH oxidase. The Nectary enzyme complex was distinct by migration on gels from the leaf enzyme complex. Temporal expression patterns demonstrated that the superoxide production (NADPH oxidase activity) was coordinated with nectar secretion, the expression of Nectarin I (a superoxide dismutase in nectar), and the expression of NOX1, a putative gene for a Nectary NADPH oxidase that was cloned from nectaries and identified as an rbohD-like NADPH oxidase. Further, in situ hybridization studies indicated that the NADPH oxidase was expressed in the early stages of flower development although superoxide was generated at later stages (after Stage 10), implicating posttranslational regulation of the NADPH oxidase in the Nectary.
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a major function of the tobacco floral Nectary is defense against microbial attack
Plant Systematics and Evolution, 2003Co-Authors: Robert W Thornburg, Clay J. Carter, Ann L T Powell, Ron Mittler, Ludmila Rizhsky, Harry T HornerAbstract:We have characterized the major nectar protein (Nectarin I) from ornamental tobacco as a superoxide dismutase that functions to generate high levels of hydrogen peroxide in nectar. Other nectar functions include an anti-polygalacturonase activity that may be due to a polygalacturonase inhibiting protein (PGIP). We also examined the expression of defense related genes in the Nectary gland by two independent methods. We isolated a sample of Nectary-expressed cDNAs and found that 21% of these cDNAs were defense related clones. Finally, we examined the expression of a number of specific defense-related genes by hybridization to specific cDNAs. These results demonstrated that a number of specific defense genes were more strongly expressed in the floral Nectary than in the foliage. Taken together these results indicate that the floral Nectary gland can have specific functions in plant defense.
Sebastian Anton - One of the best experts on this subject based on the ideXlab platform.
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Floral Nectary, nectar production dynamics and chemical composition in five nocturnal Oenothera species (Onagraceae) in relation to floral visitors
Planta, 2017Co-Authors: Sebastian Anton, Elwira Komoń-janczara, Bożena DenisowAbstract:Main conclusion The floral nectars were sucrose-dominant; however, nectar protein and amino acid contents differed, indicating that composition of nitrogenous compounds may vary considerably even between closely related plant species, irrespectively of Nectary structure. Numerous zoophilous plants attract their pollinators by offering floral nectar; an aqueous solution produced by specialized secretory tissues, known as floral nectaries. Although many papers on nectaries and nectar already exist, there has been a little research into the structure of nectaries and/or nectar production and composition in species belonging to the same genus. To redress this imbalance, we sought, in the present paper, to describe the floral Nectary, nectar production, and nectar composition in five nocturnal Oenothera species with respect to their floral visitors. The structure of nectaries was similar for all the species investigated, and comprised the epidermis (with nectarostomata), numerous layers of Nectary parenchyma, and subsecretory parenchyma. Anthesis for a single flower was short (ca. 10–12 h), and flowers lasted only one night. The release of floral nectar commenced at the bud stage (approx. 4 h before anthesis) and nectar was available to pollinators until petal closure. Nectar concentration was relatively low (ca. 27%) and the nectar was sucrose-dominant, and composed mainly of sucrose, glucose and fructose. The protein content of the nectar was also relatively low (on average, 0.31 µg ml^−1). Nevertheless, a great variety of amino acids, including both protein and non-protein types, was detected in the nectar profile of the investigated taxa. We noted both diurnal and nocturnal generalist, opportunistic floral insect visitors.
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Nectary and gender biased nectar production in dichogamous chamaenerion angustifolium l scop onagraceae
Plant Species Biology, 2017Co-Authors: Sebastian Anton, Bozena Denisow, Elwira Komonjanczara, Zdzislaw TargonskiAbstract:In dichogamous plants, nectar characteristics (i.e. nectar amount and its composition) can differ between sexual phases. In the present study, we investigated the structural organization of the floral Nectary, nectar production and carbohydrate composition in the protandrous Chamaenerion angustifolium (L.) Scop. (Onagraceae). The receptacular Nectary consisted of an epidermis with numerous nectarostomata, several layers of photosynthetic secretory parenchyma, and subsecretory parenchyma. Nectariferous tissue was not directly vascularized and starch grains were rarely observed in the secretory cells, occurring exclusively in the guard cells of modified stomata. The nectar was released via nectarostomata. The floral nectar was hexose rich (32.8/39.1/28.1% glucose/fructose/sucrose) and the total concentration was constant throughout the anthesis (47% on average). However, contrasting patterns in nectar amount and carbohydrate composition between the floral sexual phases were observed. On average, female‐phased flowers produced 1.4‐fold more nectar than male‐phased flowers, and although the nectar was sucrose rich during the male phase, it was hexose rich during the female phase, suggesting sucrose hydrolysis.
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floral Nectary nectar production dynamics and chemical composition in five nocturnal oenothera species onagraceae in relation to floral visitors
Planta, 2017Co-Authors: Sebastian Anton, Elwira Komonjanczara, Bozena DenisowAbstract:Main conclusion The floral nectars were sucrose-dominant; however, nectar protein and amino acid contents differed, indicating that composition of nitrogenous compounds may vary considerably even between closely related plant species, irrespectively of Nectary structure.
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floral nectar production and carbohydrate composition and the structure of receptacular nectaries in the invasive plant bunias orientalis l brassicaceae
Protoplasma, 2016Co-Authors: Bozena Denisow, Marzena Masierowska, Sebastian AntonAbstract:The data relating to the nectaries and nectar secretion in invasive Brassicacean taxa are scarce. In the present paper, the nectar production and nectar carbohydrate composition as well as the morphology, anatomy and ultrastructure of the floral nectaries in Bunias orientalis were investigated. Nectary glands were examined using light, fluorescence, scanning electron and transmission electron microscopy. The quantities of nectar produced by flowers and total sugar mass in nectar were relatively low. Total nectar carbohydrate production per 10 flowers averaged 0.3 mg. Nectar contained exclusively glucose (G) and fructose (F) with overall G/F ratio greater than 1. The flowers of B. orientalis have four nectaries placed at the base of the ovary. The nectarium is intermediate between two Nectary types: the lateral and median Nectary type (lateral and median glands stay separated) and the annular Nectary type (both nectaries are united into one). Both pairs of glands represent photosynthetic type and consist of epidermis and glandular tissue. However, they differ in their shape, size, secretory activity, dimensions of epidermal and parenchyma cells, thickness of secretory parenchyma, phloem supply, presence of modified stomata and cuticle ornamentation. The cells of nectaries contain dense cytoplasm, plastids with starch grains and numerous mitochondria. Companion cells of phloem lack cell wall ingrowths. The ultrastructure of secretory cells indicates an eccrine mechanism of secretion. Nectar is exuded throughout modified stomata.
