Project description:Many angiosperms can secret at least two types of sugar-rich liquids, floral nectar (FN) and extrafloral nectar (EFN), by which plants can make use of the animal partner’s mobility for pollen transportation and attract predatory animals for indirect defense. Both FN and EFN contain considerable amount of proteins which play important roles in nectar biosynthesis process and protection. Hemerocallis citrina (HC) can secrete both FN and EFN on flower during the same developmental stage. Our objective was to compare the HC FN and EFN proteome to understand the difference between their biosynthesis and ecological function. FN was collected from adult HC flowers and concentrated by ultrafiltering. EFN was collected from young HC flower buds and concentrated by ultrafiltering. Proteins were digested with trypsin then analyzed by LC-MS/MS. HSPs are the main protein identified in HC FN but their function in floral nectar is still largely unknown. PR proteins are the main protein identified in HC EFN with antimicrobial activity. Our data provide a good characterization of a monocot nectar proteome. These data, may be useful in understanding the generation process and ecological function of floral and extrafloral nectar.
Project description:Floral nectar is a rich secretion produced by nectaries offered as an attractive reward to pollinators. Floral nectaries secrete an aqueous solution largely composed of sugars and amino acids as well as an array of proteins called nectarins. These provide one of the main mechanisms of floral defense in Nicotiana nectar. Due to its composition, floral nectar provides an ideal source of nutrients for specialized microorganisms that can change the nectar composition. Understanding of floral defenses and the role of nectar proteins is essential to predict the impacts in microbial growth, nectar composition, and relationships between plants and pollinators. In order to deepen knowledge about Nicotiana spp. nectar proteins, we used LC-MS/MS-based comparative proteomic analysis to identify 22 proteins from Petunia hybrida, 35 proteins from Datura stramonium, and 144 proteins from 23 different species of Nicotiana. GO enrichment analysis and secretory signal peptide prediction demonstrated that defense/stress was the largest group of proteins in nectars with differential abundance and distribution throughout genus Nicotiana. The Nicotiana spp. proteome consisted of 105 exclusive proteins such as lipid transfer proteins (LTPs), Nectar Redox Cycle proteins, proteases inhibitors (PI), and PR-proteins. Analysis by taxonomic sections demonstrated that LTPs were the most abundant group of proteins in the nectar of Undulatae and Noctiflora sections while nectarins were more abundant proteins in Rusticae, Suaveolens, Polydicliae, and Alata sections. Peroxidases (Pox) and chitinases (Chit) were exclusive to P. hybrida nectar, while D. stramonium proteome had only seven unique proteins. Significant differences were identified between the proteome of taxonomic sections providing relevant insights into the group of proteins related to defense/stress associated with Nectar Redox Cycle, antimicrobial proteins and signaling pathways. The activity of floral nectar proteins is suggested impact the microbial growth. The knowledge about these proteomes provides significant insights into the diversity of proteins secreted in the nectars and the array of mechanisms used by Nicotiana spp. in its floral defense.
Project description:Bacterial community in floral nectar of Nicotiana glauca: The roles of environmental versus spatial factors along climatic gradient and across the globe
Project description:Floral nectar plays important roles in the interaction between animal-pollinated plants and pollinators. Growing empirical evidence shows that most of the proteins secreted in nectar (nectarins) are enzymes that can tailor nectar chemistry for their animal mutualists or reduce the growth of microorganisms in nectar. However, to date, the function of many nectarins remains unknown, and very few plant species have had their nectar proteome thoroughly investigated. Mucuna sempervirens (Fabaceae) is a perennial woody vine native to China. Nectarins from this species were separated using two-dimensional gel electrophoresis, and analyzed using mass spectrometry. A L-gulonolactone oxidase like protein (MsGulLO) was detected. MsGulLO has high similarity to L-gulonolactone oxidase 5 (AtGulLO5) in Arabidopsis thaliana, which was suggested to be involved in the pathway of ascorbate biosynthesis; however both MsGulLO and AtGulLO5 are divergent from animal L-gulonolactone oxidases. MsGulLO is suggested to function in hydrogen peroxide generation in nectar but not in plant ascorbate biosynthesis.
Project description:Floral nectar proteins (nectarins) are mainly enzymes and play important roles in inhibiting microbial growth in nectar and tailoring nectar chemistry before or after secretory. Nectar proteomes are usually small, but only very few plant species have had their nectar proteomes thoroughly investigated. Nectarins from Nicotiana tabacum (NT) were separated using two-dimensional gel electrophoresis, and then analyzed using mass spectrometry. Glycoproteins were isolated from raw NT nectar, separated by SDS-PAGE, and identified by mass spectrometry. All eight identified nectarins and four invertase genes’ expression were analysed by qPCR. Sugars composition, total sugar concentration, protein content, polyphenol content and hydrogen peroxide content were compared at different time intervals in extracted nectar and nectar in situ after secretion. Totally, eight nectarins were detected in NT nectar in which only two are glycoproteins, beta-xylosidase and a protein with unknown function. All of the eight nectarin genes expression was not nectary-specific and not synchronous along with the nectary development. After secretion, NT nectar in flower tube changed from sucrose–rich to hexose-rich type even though no free invertase or its activity was detected in NT nectar. No sugar composition changes observed in extracted nectar after incubating at 30 ℃ up to 48 hours in plastic tubes. Our results indicate that nectar post-secretory changes could be a complex process and tissue closely contact with nectar might function in it.
Project description:The goal of the research is to identify the physiological pathways that influence survival, growth, and competitive ability of the species of yeast that colonize floral nectar. Initially sterile, floral nectar is colonized by multiple species of microbes via insects and birds that visit the flowers for nectar. Once colonized, the microbes face two major challenges of the nectar environment: high osmotic pressure, caused by excessive carbon supply, and strong resource competition, caused by low nitrogen availability. We propose to study the genetic basis of the unique ecological strategies that allow nectar yeasts to cope with these challenges, and to determine the effects that these genes may have on microbe microbe interactions in nectar and the chemical properties of nectar that affect pollinator preference.
The work (proposal:https://doi.org/10.46936/10.25585/60001130) conducted by the U.S. Department of Energy Joint Genome Institute (https://ror.org/04xm1d337), a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy operated under Contract No. DE-AC02-05CH11231.
Project description:Nectaries are the glands responsible for nectar secretion. To understand the genetic programming underlying nectar production, floral nectaries of six Nicotiana species at four different time points (floral stage 6,9, and 12, a post-secretory stage) in biological triplicate were collected, with RNA being isolated and subjected to Illumina RNA-seq analysis.
Project description:The black nectar of Melianthus flowers is thought to serve as a visual attractant to pollinators, but the chemical identity and synthesis of the black pigment are unknown. Here we report that the black nectar contains a natural analog of iron-gall ink, which humans have used since medieval times. Specifically, dark black nectar at anthesis contains high levels of ellagic acid and iron; synthetic solutions of ellagic acid and iron(III) recapitulate the black color of the nectar. Conversely, lightly colored nectars before and after anthesis contain significantly lower levels of ellagic acid and iron, but higher levels of gallic acid. We then explored the possibility of post-secretory synthesis of ellagic acid from gallic acid. Indeed, Melianthus nectar contains a peroxidase that oxidizes gallic acid to form ellagic acid. Reactions containing the nectar peroxidase, gallic acid, hydrogen peroxide, and iron can fully recreate the black color of the nectar. Visual modeling indicates that the black color is both visible and conspicuous to birds within the context of the flower. In summary, the black nectar of Melianthus is derived from an ellagic acid-Fe complex analogous to iron-gall ink and is likely involved in the attraction of passerine bird pollinators.