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Clay J. Carter - One of the best experts on this subject based on the ideXlab platform.
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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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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.
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The pennycress (Thlaspi arvense L.) Nectary: structural and transcriptomic characterization.
BMC Plant Biology, 2017Co-Authors: Jason B. Thomas, Kevin M. Dorn, Marshall Hampton, M. David Marks, Clay J. CarterAbstract:Pennycress [Thlaspi arvense L (Brassicaceae)] is being domesticated as a renewable biodiesel feedstock that also provides crucial ecosystems services, including as a nutritional resource for pollinators. However, its flowers produce significantly less Nectar than other crop relatives in the Brassicaceae. This study was undertaken to understand the basic biology of the pennycress Nectary as an initial step toward the possibility of enhancing Nectar output from its flowers. Pennycress flowers contain four equivalent Nectaries located extrastaminally at the base of the insertion sites of short and long stamens. Like other Brassicaceae, the Nectaries have open stomates on their surface, which likely serve as the sites of Nectar secretion. The Nectaries produce four distinct Nectar droplets that accumulate in concave structures at the base of each of the four petals. To understand the molecular biology of the pennycress Nectary, RNA was isolated from ‘immature’ (pre-secretory) and ‘mature’ (secretory) Nectaries and subjected to RNA-seq. Approximately 184 M paired-end reads (368 M total reads) were de novo assembled into a total of 16,074 independent contigs, which mapped to 12,335 unique genes in the pennycress genome. Nearly 3700 genes were found to be differentially expressed between immature and mature Nectaries and subjected to gene ontology and metabolic pathway analyses. Lastly, in silico analyses identified 158 pennycress orthologs to Arabidopsis genes with known enriched expression in Nectaries. These Nectary-enriched expression patterns were verified for select pennycress loci by semi-quantitative RT-PCR. Pennycress Nectaries are unique relative to those of other agriculturally important Brassicaceae, as they contain four equivalent Nectaries that present their Nectar in specialized cup-shaped structures at the base of the petals. In spite of these morphological differences, the genes underlying the regulation and production of Nectar appear to be largely conserved between pennycress and Arabidopsis thaliana. These results provide a starting point for using forward and reverse genetics approaches to enhance Nectar synthesis and secretion in pennycress.
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identification of differential gene expression in brassica rapa Nectaries through expressed sequence tag analysis
PLOS ONE, 2010Co-Authors: Marshall Hampton, Brian W Kram, Emily M Chambers, Jerad S Ehrnriter, Jonathan H Gralewski, Teresa Joyal, Clay J. CarterAbstract:Background Nectaries are the floral organs responsible for the synthesis and secretion of Nectar. Despite their central roles in pollination biology, very little is understood about the molecular mechanisms underlying Nectar production. This project was undertaken to identify genes potentially involved in mediating Nectary form and function in Brassica rapa. Methodology and Principal Findings Four cDNA libraries were created using RNA isolated from the median and lateral Nectaries of B. rapa flowers, with one normalized and one non-normalized library being generated from each tissue. Approximately 3,000 clones from each library were randomly sequenced from the 5′ end to generate a total of 11,101 high quality expressed sequence tags (ESTs). Sequence assembly of all ESTs together allowed the identification of 1,453 contigs and 4,403 singleton sequences, with the Basic Localized Alignment Search Tool (BLAST) being used to identify 4,138 presumptive orthologs to Arabidopsis thaliana genes. Several genes differentially expressed between median and lateral Nectaries were initially identified based upon the number of BLAST hits represented by independent ESTs, and later confirmed via reverse transcription polymerase chain reaction (RT PCR). RT PCR was also used to verify the expression patterns of eight putative orthologs to known Arabidopsis Nectary-enriched genes. Conclusions/Significance This work provided a snapshot of gene expression in actively secreting B. rapa Nectaries, and also allowed the identification of differential gene expression between median and lateral Nectaries. Moreover, 207 orthologs to known Nectary-enriched genes from Arabidopsis were identified through this analysis. The results suggest that genes involved in Nectar production are conserved amongst the Brassicaceae, and also supply clones and sequence information that can be used to probe Nectary function in B. rapa.
Massimo Nepi - One of the best experts on this subject based on the ideXlab platform.
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Nectaries and male-biased Nectar production in protandrous flowers of a perennial umbellifer Angelica sylvestris L. (Apiaceae)
Plant Systematics and Evolution, 2015Co-Authors: Malgorzata Stpiczynska, Massimo Nepi, Marcin ZychAbstract:Nectar is the most common floral pollinator reward. In dichogamous species, floral Nectar production rates can differ between sexual phases. We studied the structure of Nectaries located on the stylopodium and Nectar production in protandrous umbellifer Angelica sylvestris . Our study species produced Nectar in both floral sexual phases. Nectar sugar concentration was low (on average 22 ± 11 %, mean ± SD) and the Nectar hexose rich and composed of sucrose, glucose, fructose and a small amount of amino acids, including β-alanine, a non-protein amino acid. Although Nectar composition and sugar concentration varied little between floral sexual phases, Nectar production showed a threefold reduction during the stigma receptive period. This is in contrast to other studies of Apiaceae that have reported female-biased Nectar production, but in the direction predicted by plant sexual selection theory, suggesting that in pollen-unlimited species, floral rewards mainly enhance male reproductive success. The structure of the Nectary was similar at the two sexual stages investigated, and composed of a secretory epidermis and several layers of Nectariferous and subsecretory parenchyma. The Nectary cells were small, had large nuclei, numerous small vacuoles and dense, intensely staining cytoplasm with abundant endoplasmic reticulum, mitochondria and secretory vesicles. They contained abundant resin-like material that may potentially act as defence against microbes. Starch was rarely observed in the Nectary cells, occurring predominantly at the female stage and mainly in guard and parenchyma cells in close proximity to stomata, and in subsecretory parenchyma. The main route of Nectar release in A. sylvestris seems to be via modified stomata.
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Nectar sugars and bird visitation define a floral niche for basidiomycetous yeast on the Canary Islands
BMC Ecology, 2015Co-Authors: Moritz Mittelbach, Daniele Nocentini, Massimo Nepi, Andrey M Yurkov, Maximilian Weigend, Dominik BegerowAbstract:Background Studies on the diversity of yeasts in floral Nectar were first carried out in the late 19^th century. A narrow group of fermenting, osmophilous ascomycetes were regarded as exclusive specialists able to populate this unique and species poor environment. More recently, it became apparent that microorganisms might play an important role in the process of plant pollination. Despite the importance of these Nectar dwelling yeasts, knowledge of the factors that drive their diversity and species composition is scarce. Results In this study, we linked the frequencies of yeast species in floral Nectars from various host plants on the Canary Islands to Nectar traits and flower visitors. We estimated the structuring impact of pollination syndromes (Nectar volume, sugar concentration and sugar composition) on yeast diversity. The observed total yeast diversity was consistent with former studies, however, the present survey yielded additional basidiomycetous yeasts in unexpectedly high numbers. Our results show these basidiomycetes are significantly associated with ornithophilous flowers. Specialized ascomycetes inhabit sucrose-dominant Nectars, but are surprisingly rare in Nectar dominated by monosaccharides. Conclusions There are two conclusions from this study: (i) a shift of floral visitors towards ornithophily alters the likelihood of yeast inoculation in flowers, and (ii) low concentrated hexose-dominant Nectar promotes colonization of flowers by basidiomycetes. In the studied floral system, basidiomycete yeasts are acknowledged as regular members of Nectar. This challenges the current understanding that Nectar is an ecological niche solely occupied by ascomycetous yeasts.
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secretion and composition of Nectar and the structure of perigonal Nectaries in fritillaria meleagris l liliaceae
Plant Systematics and Evolution, 2012Co-Authors: Malgorzata Stpiczynska, Massimo Nepi, Marcin ZychAbstract:The structure of perigonal Nectaries, Nectar production and carbohydrate composition were compared at various stages in the lifespan of the flower of Fritillaria meleagris L. The six Nectaries each occupied a groove that is located 2–4 mm above the tepal base. The average Nectary measured 11.0 mm long and 1.0–1.2 mm wide. The structure of Nectaries situated on both inner and outer tepal whorls was identical, and at anthesis they were equally accessible to potential pollinators. However, secretion from Nectaries associated with inner tepals tended to exceed that produced by Nectaries located on the outer tepals. On average, regardless of flower stage, one flower secreted 10.87 ± 12.98 mg of Nectar (mean and SD; N = 182). The Nectar concentration ranged between 3 and 75%, with average concentration of sugars exceeding 50%. Both Nectar production and concentration were dependent on the stage of anthesis, with the highest scores being recorded during full anthesis (21.75 ± 16.08 mg; 70.5%, mass and concentration, respectively) and the lowest at the end of anthesis (1.32 ± 2.69 mg; 16.9%, mass and concentration, respectively). A decline in both mass of Nectar secreted and Nectar concentration during the final stage of anthesis indicates Nectar resorption. Nectar was composed of sucrose, glucose and fructose in approx. equal quantities, and its composition did not change significantly during subsequent stages of flowering. The Nectaries comprised a single-layered secretory epidermis and several layers of subepidermal parenchyma. The Nectariferous cells did not accumulate starch during any of the investigated stages. The Nectary was supplied with one large and several smaller vascular bundles comprising xylem and phloem. Transport of assimilates and Nectar secretion by protoplasts of secretory cells (and probably also Nectar resorption) were facilitated by cell wall ingrowths present on the tangential walls of epidermal cells and subepidermal parenchyma. Epidermal cells lacked stomata. Nectar passed across the cell wall and through the cuticle which was clearly perforated with pores.
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Ecophysiological aspects of Nectar reabsorption
Acta Agrobotanica, 2012Co-Authors: Malgorzata Stpiczynska, Massimo NepiAbstract:A number of approaches, both direct and indirect, have shown that Nectar is reabsorbed by numerous plant species, irrespective of the age or sex of the flower. Furthermore, reabsorption occurs regardless of whether or not the flower has been pollinated. Reabsorption helps to maintain concentration of Nectar and their viscosity and thereby encourages continued visits by pollinators. Conversely, the capacity to vary concentration of Nectar sugars may confer evolutionary advantage by encouraging visits by more than one kind of pollinator and this is particularly important in regions where there is a paucity of pollinators. A further important role of Nectar reabsorption is the maintenance of the energy equilibrium of the plant. A number of studies have shown that Nectar production involves considerable energy expenditure requiring as much as 37% of the plant's daily production of energy by photosynthesis. The increased metabolic costs incurred by the plant during Nectar production and secretion can reduce its growth and reproduction during the following season. Reabsorption of Nectar that has not been collected by pollinators enables the plant to conserve at least some of the energy reserved for the secretion of Nectar. Sugars reabsorbed from Nectar can be re-used for the development of fruit and ovules - processes which demand large quantities of sugar. Despite convincing evidence for the reabsorption of Nectar, few detailed studies have addressed the transport and incorporation of reabsorbed sugars. One of the questions that remain to be answered is 'What is the cellular basis for Nectar reabsorption by the Nectary?'
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DYNAMICS OF Nectar PRODUCTION AND Nectar HOMEOSTASIS IN MALE FLOWERS OF CUCURBITA PEPO L.
International Journal of Plant Sciences, 2011Co-Authors: Massimo Nepi, Massimo Guarnieri, Laura Cresti, Ettore PaciniAbstract:Male flowers of Cucurbita pepo L. cv. Alberello di Sarzana produce Nectar in the first hours of anthesis (5:00 a.m.–8:00 a.m.). However, Nectar production ceases soon after 9:00 a.m. Removal of Nectar had no effect on total Nectar volume and sugar concentration. Nectar substitution experiments were performed using low (20 μL) and high (100 μL) Nectar volumes in combination with low (10%) and high (60%) Nectar sugar concentrations. Experiments were performed during the Nectar production phase (5:00 a.m.) and after the cessation phase began (10:00 a.m.). In both phases, high-volume treatments tended to reverse the passage of water from the Nectary to the Nectar. Although reabsorption of water and sugar is more obvious after the commencement of the cessation phase, and especially during high-concentration treatments, it can also occur during the secretory phase, thereby demonstrating that the flowers are able to secrete and reabsorb water and sugar independently throughout the whole of anthesis. This is very...
Marshall Hampton - One of the best experts on this subject based on the ideXlab platform.
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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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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.
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The pennycress (Thlaspi arvense L.) Nectary: structural and transcriptomic characterization.
BMC Plant Biology, 2017Co-Authors: Jason B. Thomas, Kevin M. Dorn, Marshall Hampton, M. David Marks, Clay J. CarterAbstract:Pennycress [Thlaspi arvense L (Brassicaceae)] is being domesticated as a renewable biodiesel feedstock that also provides crucial ecosystems services, including as a nutritional resource for pollinators. However, its flowers produce significantly less Nectar than other crop relatives in the Brassicaceae. This study was undertaken to understand the basic biology of the pennycress Nectary as an initial step toward the possibility of enhancing Nectar output from its flowers. Pennycress flowers contain four equivalent Nectaries located extrastaminally at the base of the insertion sites of short and long stamens. Like other Brassicaceae, the Nectaries have open stomates on their surface, which likely serve as the sites of Nectar secretion. The Nectaries produce four distinct Nectar droplets that accumulate in concave structures at the base of each of the four petals. To understand the molecular biology of the pennycress Nectary, RNA was isolated from ‘immature’ (pre-secretory) and ‘mature’ (secretory) Nectaries and subjected to RNA-seq. Approximately 184 M paired-end reads (368 M total reads) were de novo assembled into a total of 16,074 independent contigs, which mapped to 12,335 unique genes in the pennycress genome. Nearly 3700 genes were found to be differentially expressed between immature and mature Nectaries and subjected to gene ontology and metabolic pathway analyses. Lastly, in silico analyses identified 158 pennycress orthologs to Arabidopsis genes with known enriched expression in Nectaries. These Nectary-enriched expression patterns were verified for select pennycress loci by semi-quantitative RT-PCR. Pennycress Nectaries are unique relative to those of other agriculturally important Brassicaceae, as they contain four equivalent Nectaries that present their Nectar in specialized cup-shaped structures at the base of the petals. In spite of these morphological differences, the genes underlying the regulation and production of Nectar appear to be largely conserved between pennycress and Arabidopsis thaliana. These results provide a starting point for using forward and reverse genetics approaches to enhance Nectar synthesis and secretion in pennycress.
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PIN6 is required for Nectary auxin response and short stamen development
Plant Journal, 2013Co-Authors: Ricci L. Bender, Marshall Hampton, Peter M Klinkenberg, Megan L. Fekete, Brittany Bauer, Matthew Malecha, Khrystyne Lindgren, Jennifer A. Maki, M. Ann D. N. Perera, Basil J. NikolauAbstract:†‡ SUMMARY The PIN family of proteins is best known for its involvement in polar auxin transport and tropic responses. PIN6 (At1g77110) is one of the remaining PIN family members in Arabidopsis thaliana to which a biological function has not yet been ascribed. Here we report that PIN6 is a Nectary-enriched gene whose expression level is positively correlated with total Nectar production in Arabidopsis, and whose function is required for the proper development of short stamens. PIN6 accumulates in internal membranes consistent with the ER, and multiple lines of evidence demonstrate that PIN6 is required for auxin-dependent responses in Nectaries. Wild-type plants expressing auxin-responsive DR5:GFP or DR5:GUS reporters displayed intense signal in lateral Nectaries, but pin6 lateral Nectaries showed little or no signal for these reporters. Further, exogenous auxin treatment increased Nectar production more than tenfold in wild-type plants, but Nectar production was not increased in pin6 mutants when treated with auxin. Conversely, the auxin transport inhibitor N‐1‐naphthylphthalamic acid (NPA) reduced Nectar production in wild-type plants by more than twofold, but had no significant effect on pin6 lines. Interestingly, a MYB57 transcription factor mutant, myb57‐2, closely phenocopied the loss-of-function mutant pin6‐2. However, PIN6 expression was not dependent on MYB57, and RNA-seq analyses of pin6‐2 and myb57‐2 mutant Nectaries showed little overlap in terms of differentially expressed genes. Cumulatively, these results demonstrate that PIN6 is required for proper auxin response and Nectary function in Arabidopsis. These results also identify auxin as an important factor in the regulation of Nectar production, and implicate short stamens in the maturation of lateral Nectaries.
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identification of differential gene expression in brassica rapa Nectaries through expressed sequence tag analysis
PLOS ONE, 2010Co-Authors: Marshall Hampton, Brian W Kram, Emily M Chambers, Jerad S Ehrnriter, Jonathan H Gralewski, Teresa Joyal, Clay J. CarterAbstract:Background Nectaries are the floral organs responsible for the synthesis and secretion of Nectar. Despite their central roles in pollination biology, very little is understood about the molecular mechanisms underlying Nectar production. This project was undertaken to identify genes potentially involved in mediating Nectary form and function in Brassica rapa. Methodology and Principal Findings Four cDNA libraries were created using RNA isolated from the median and lateral Nectaries of B. rapa flowers, with one normalized and one non-normalized library being generated from each tissue. Approximately 3,000 clones from each library were randomly sequenced from the 5′ end to generate a total of 11,101 high quality expressed sequence tags (ESTs). Sequence assembly of all ESTs together allowed the identification of 1,453 contigs and 4,403 singleton sequences, with the Basic Localized Alignment Search Tool (BLAST) being used to identify 4,138 presumptive orthologs to Arabidopsis thaliana genes. Several genes differentially expressed between median and lateral Nectaries were initially identified based upon the number of BLAST hits represented by independent ESTs, and later confirmed via reverse transcription polymerase chain reaction (RT PCR). RT PCR was also used to verify the expression patterns of eight putative orthologs to known Arabidopsis Nectary-enriched genes. Conclusions/Significance This work provided a snapshot of gene expression in actively secreting B. rapa Nectaries, and also allowed the identification of differential gene expression between median and lateral Nectaries. Moreover, 207 orthologs to known Nectary-enriched genes from Arabidopsis were identified through this analysis. The results suggest that genes involved in Nectar production are conserved amongst the Brassicaceae, and also supply clones and sequence information that can be used to probe Nectary function in B. rapa.
Hans Jacquemyn - One of the best experts on this subject based on the ideXlab platform.
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Sweet Scents: Nectar Specialist Yeasts Enhance Nectar Attraction of a Generalist Aphid Parasitoid Without Affecting Survival.
Frontiers in plant science, 2018Co-Authors: Islam S. Sobhy, Dieter Baets, Tim Goelen, Beatriz Herrera-malaver, Lien Bosmans, Wim Van Den Ende, Kevin J. Verstrepen, Felix L. Wäckers, Hans Jacquemyn, Bart LievensAbstract:Floral Nectar is commonly inhabited by microorganisms, mostly yeasts and bacteria, which can have a strong impact on Nectar chemistry and scent. Yet, little is known about the effects of Nectar microbes on the behavior and survival of insects belonging to the third trophic level such as parasitoids. Here, we used five Nectar-inhabiting yeast species to test the hypothesis that yeast species that almost solely occur in Nectar, and therefore substantially rely on floral visitors for dispersal, produce volatile compounds that enhance insect attraction without compromising insect life history parameters, such as survival. Experiments were performed using two Nectar specialist yeasts (Metschnikowia gruessii and M. reukaufii) and three generalist species (Aureobasidium pullulans, Hanseniaspora uvarum and Sporobolomyces roseus). Saccharomyces cerevisiae was included as a reference strain. We compared olfactory responses of the generalist aphid parasitoid Aphidius ervi (Haliday) (Hymenoptera: Braconidae) when exposed to these microorganisms inoculated in synthetic Nectar. Nectar-inhabiting yeasts had a significant impact on Nectar chemistry and produced distinct volatile blends, some of which were attractive, while others were neutral or repellent. Among the different yeast species tested, the Nectar specialists M. gruessii and M. reukaufii were the only species that produced a highly attractive Nectar to parasitoid females, which simultaneously had no adverse effects on longevity and survival of adults. By contrast, parasitoids that fed on Nectars fermented with the reference strain, A. pullulans, H. uvarum or S. roseus showed shortest longevity and lowest survival. Additionally, Nectars fermented by A. pullulans or S. roseus were consumed significantly less, suggesting a lack of important nutrients or undesirable changes in the Nectar chemical profiles. Altogether our results indicate that Nectar-inhabiting yeasts play an important, but so far largely overlooked, role in plant-insect interactions by modulating the chemical composition of Nectar, and may have important ecological consequences for plant pollination and biological control of herbivorous insects.
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The impact of Nectar chemical features on phenotypic variation in two related Nectar yeasts.
FEMS microbiology ecology, 2015Co-Authors: Maria I Pozo, Carlos M Herrera, Wim Van Den Ende, Kevin J. Verstrepen, Bart Lievens, Hans JacquemynAbstract:Floral Nectars become easily colonized by microbes, most often species of the ascomycetous yeast genus Metschnikowia. Although it is known that Nectar composition can vary tremendously among plant species, most probably corresponding to the nutritional requirements of their main pollinators, far less is known about how variation in Nectar chemistry affects intraspecific variation in Nectarivorous yeasts. Because variation in Nectar traits probably affects growth and abundance of Nectar yeasts, Nectar yeasts can be expected to display large phenotypic variation in order to cope with varying Nectar conditions. To test this hypothesis, we related variation in the phenotypic landscape of a vast collection of Nectar-living yeast isolates from two Metschnikowia species (M. reukaufii and M. gruessii) to Nectar chemical traits using non-linear redundancy analyses. Nectar yeasts were collected from 19 plant species from different plant families to include as much variation in Nectar chemical traits as possible. As expected, Nectar yeasts displayed large variation in phenotypic traits, particularly in traits related to growth performance in carbon sources and inhibitors, which was significantly related to the host plant from which they were isolated. Total sugar concentration and relative fructose content significantly explained the observed variation in the phenotypic profile of the investigated yeast species, indicating that sugar concentration and composition are the key traits that affect phenotypic variation in Nectarivorous yeasts.
Brian W Kram - One of the best experts on this subject based on the ideXlab platform.
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identification of differential gene expression in brassica rapa Nectaries through expressed sequence tag analysis
PLOS ONE, 2010Co-Authors: Marshall Hampton, Brian W Kram, Emily M Chambers, Jerad S Ehrnriter, Jonathan H Gralewski, Teresa Joyal, Clay J. CarterAbstract:Background Nectaries are the floral organs responsible for the synthesis and secretion of Nectar. Despite their central roles in pollination biology, very little is understood about the molecular mechanisms underlying Nectar production. This project was undertaken to identify genes potentially involved in mediating Nectary form and function in Brassica rapa. Methodology and Principal Findings Four cDNA libraries were created using RNA isolated from the median and lateral Nectaries of B. rapa flowers, with one normalized and one non-normalized library being generated from each tissue. Approximately 3,000 clones from each library were randomly sequenced from the 5′ end to generate a total of 11,101 high quality expressed sequence tags (ESTs). Sequence assembly of all ESTs together allowed the identification of 1,453 contigs and 4,403 singleton sequences, with the Basic Localized Alignment Search Tool (BLAST) being used to identify 4,138 presumptive orthologs to Arabidopsis thaliana genes. Several genes differentially expressed between median and lateral Nectaries were initially identified based upon the number of BLAST hits represented by independent ESTs, and later confirmed via reverse transcription polymerase chain reaction (RT PCR). RT PCR was also used to verify the expression patterns of eight putative orthologs to known Arabidopsis Nectary-enriched genes. Conclusions/Significance This work provided a snapshot of gene expression in actively secreting B. rapa Nectaries, and also allowed the identification of differential gene expression between median and lateral Nectaries. Moreover, 207 orthologs to known Nectary-enriched genes from Arabidopsis were identified through this analysis. The results suggest that genes involved in Nectar production are conserved amongst the Brassicaceae, and also supply clones and sequence information that can be used to probe Nectary function in B. rapa.
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cell wall invertase 4 is required for Nectar production in arabidopsis
Journal of Experimental Botany, 2010Co-Authors: Jeffrey M Ruhlmann, Brian W Kram, Clay J. CarterAbstract:To date, no genes have been reported to directly affect the de novo production of floral Nectar. In an effort to identify genes involved in Nectar production, the Affymetrix® ATH1 GeneChip was previously used to examine global gene expression profiles in Arabidopsis thaliana Nectaries. One of the genes displaying highly enriched expression in Nectaries was CELL WALL INVERTASE 4 (AtCWINV4, At2g36190), which encodes an enzyme that putatively catalyses the hydrolysis of sucrose into glucose and fructose. RT-PCR was used to confirm the Nectary-enriched expression of AtCWINV4, as well as an orthologue from Brassica rapa. To probe biological function, two independent Arabidopsis cwinv4 T-DNA mutants were isolated. Unlike wild-type plants, cwinv4 lines did not produce Nectar. While overall Nectary morphology appeared to be normal, cwinv4 flowers accumulated higher than normal levels of starch in the receptacle, but not within the Nectaries themselves. Conversely, wild-type, but not cwinv4, Nectarial stomata stained intensely for starch. Cell wall extracts prepared from mutant flowers displayed greatly reduced invertase activity when compared with wild-type plants, and cwinv4 flowers also accumulated significantly lower levels of total soluble sugar. Cumulatively, these results implicate CWINV4 as an absolutely required factor for Nectar production in the Brassicaceae, specifically by maintaining constant sink status within Nectaries, thus allowing them to accumulate the sugars necessary for Nectar production. In addition, CWINV4 is probably responsible for the hexose-rich composition observed for many Brassicaceae Nectars.
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Arabidopsisthaliana as a model for functional Nectary analysis
Sexual Plant Reproduction, 2009Co-Authors: Brian W Kram, Clay J. CarterAbstract:Nectaries and Nectar have received much research attention for well over 200 years due to their central roles in plant–pollinator interactions. Despite this, only a few genes have demonstrated impacts on Nectary development, and none have been reported to mediate de novo Nectar production. This scarcity of information is largely due to the lack of a model that combines sizeable Nectaries, and high levels of Nectar production, along with suitable genomics resources. For example, even though Arabidopsis thaliana has been useful for developmental studies, it has been largely overlooked as a model for studying Nectary function due to the small size of its flowers. However, Arabidopsis Nectaries, along with those of related species, are quite operational and can be used to discern molecular mechanisms of Nectary form and function. A current understanding of the machinery underlying Nectary function in plants is briefly presented, with emphasis placed on the prospects of using Arabidopsis as a model for studying these processes.
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Arabidopsis thaliana as a model for functional Nectary analysis.
Sexual Plant Reproduction, 2009Co-Authors: Brian W Kram, Clay J. CarterAbstract:Nectaries and Nectar have received much research attention for well over 200 years due to their central roles in plant-pollinator interactions. Despite this, only a few genes have demonstrated impacts on Nectary development, and none have been reported to mediate de novo Nectar production. This scarcity of information is largely due to the lack of a model that combines sizeable Nectaries, and high levels of Nectar production, along with suitable genomics resources. For example, even though Arabidopsis thaliana has been useful for developmental studies, it has been largely overlooked as a model for studying Nectary function due to the small size of its flowers. However, Arabidopsis Nectaries, along with those of related species, are quite operational and can be used to discern molecular mechanisms of Nectary form and function. A current understanding of the machinery underlying Nectary function in plants is briefly presented, with emphasis placed on the prospects of using Arabidopsis as a model for studying these processes.
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Uncovering the Arabidopsis thaliana Nectary transcriptome: investigation of differential gene expression in floral Nectariferous tissues
BMC Plant Biology, 2009Co-Authors: Brian W Kram, Clay J. CarterAbstract:Background Many flowering plants attract pollinators by offering a reward of floral Nectar. Remarkably, the molecular events involved in the development of Nectaries, the organs that produce Nectar, as well as the synthesis and secretion of Nectar itself, are poorly understood. Indeed, to date, no genes have been shown to directly affect the de novo production or quality of floral Nectar. To address this gap in knowledge, the ATH1 Affymetrix^® GeneChip array was used to systematically investigate the Arabidopsis Nectary transcriptome to identify genes and pathways potentially involved in Nectar production. Results In this study, we identified a large number of genes differentially expressed between secretory lateral Nectaries and non-secretory median Nectary tissues, as well as between mature lateral Nectaries (post-anthesis) and immature lateral Nectaries (pre-anthesis). Expression within Nectaries was also compared to thirteen non-Nectary reference tissues, from which 270 genes were identified as being significantly upregulated in Nectaries. The expression patterns of 14 Nectary-enriched genes were also confirmed via RT PCR. Upon looking into functional groups of upregulated genes, pathways involved in gene regulation, carbohydrate metabolism, and lipid metabolism were particularly enriched in Nectaries versus reference tissues. Conclusion A large number of genes preferentially expressed in Nectaries, as well as between Nectary types and developmental stages, were identified. Several hypotheses relating to mechanisms of Nectar production and regulation thereof are proposed, and provide a starting point for reverse genetics approaches to determine molecular mechanisms underlying Nectar synthesis and secretion.
