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.
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:A spatial transcriptomics method was developed with the 10X Genomics Visium HD platform and a custom probe panel to study expression of Major Histocompatibility Complex (MHC) genes in tissues from Mauritian-origin cynomolgus macaques. Previous scRNA sequencing studies with these macaque demonstrated a wide range of allele-specific MHC transcript levels in multiple peripheral blood mononuclear cell subsets. The restricted genetic diversity of the Mauritian macaque population made it possible to design a manageable number of custom MHC probes for this pilot study . Tissues examined included kidney, liver, lung and heart that of particular interest for transplant research. The Visium Human Transcriptome Kit v2 performed well with at least 40 different kidney cell types identified based on cell clustering with gene expression definitions in a human kidney cell atlas. In addition, higher overall transcript levels were observed for several major MHC class I alleles compared to minor alleles that tend to be expressed at low levels in peripheral blood mononuclear cells.