Proteome of pollination drops in Ephedra (Gnetales)
(English)Manuscript (preprint) (Other academic)
Proteins are important in many physiological and ecological processes. In pollination drops of gymnosperms, proteins take part in a number of pollen-ovule interactions and aid for example in ovule defense. Pollination drops in Ephedra (Gnetales) are secreted in large volumes and are known to be high in sucrose, but their proteomic profile has not been thoroughly studied. In this study, proteomic analysis of pollination drops of Ephedra was carried out based on four species: E. distachya, E. foeminea, E. likiangensis and E. minuta. Pollination drop samples were analyzed using gel electrophoresis (1D SDS-PAGE) and mass spectrometry (LC-MS analysis). Protein profile and putative function of proteins were assessed by searches against a set of proteomic databases. Results indicate that number of proteins as well as their amount was low, and most proteins belong to a degradome, i.e., they are remains of degrading tissue at the apex of the nucellus during formation of the pollination chamber. Variation among species was considerable. Ephedra foeminea, which is sister to all other species, contains more kinds of proteins than other investigated species. The closely related species E. likiangensis and E. minuta differ considerably in protein profiles. In E. distachya, no secretome was found; all detected proteins in this species are degradome. The observed differences between species may be related to pollination biology. Insect pollinated species, such as E. foeminea appear to have more proteins in their pollination drops than wind-pollinated species such as E. distachya. Many things are still uncertain regarding proteomics of pollination drops in Ephedra. Among other things, repeatability of results may be a problem; however, this study clearly shows that the amount of proteins in ephedran pollination drops is very low compared to other studied gymnosperms. Future studies of ovule defense in Ephedra should probably have another focus, and perhaps consider sugar content and carbohydrate metabolism rather than proteomics.
pollination drops, Ephedra, proteomics, mass spectrometry, evolution of pollination, ovule defense, carbohydrate metabolism
Research subject Plant Systematics
IdentifiersURN: urn:nbn:se:su:diva-128437OAI: oai:DiVA.org:su-128437DiVA: diva2:915007