Gymnosperm pollination drop proteins and their relation to function and phylogeny

dc.contributor.authorWagner, Rebecca Elizabeth
dc.contributor.supervisorAderkas, P. von of Biologyen_US of Science M.Sc.en_US
dc.description.abstractThe pollination drop is a conservative pollination mechanism observed in all major gymnosperm taxa. Despite its ubiquity and essentiality to gymnosperm reproductive success, it remains poorly understood. Recent studies identifying conifer ovular secretion proteins have indicated a more complex role for ovular secretions than pollen receipt. We used a proteomics approach to analyze the pollination drops of four gymnosperm species (Juniperus communis (common juniper), Juniperus oxycedrus (prickly juniper), Chamaecyparis lawsoniana (Port Orford cedar), and Welwitschia mirabilis). Pollination drop proteins were separated by SDS-PAGE, and the most abundant proteins were analyzed by mass spectrometry and sequenced. Based on BLAST searching of combined amino acid sequences, several proteins were identified: an 83 kDa subtilisin-like proteinase, a 62 kDa glycosyl hydrolase, a 47.5 kDa glucan 1,3-ß-glucosidase precursor, a 30 kDa chitinase, and a 25 kDa thaumatin-like protein in J. connnunis; a 30 kDa chitinase, a 25 kDa thaumatin-like protein, and a 32.5 kDa glucanase-like protein in J. oxycedrus; an 83 kDa subtilisin-like proteinase, a 62 kDa (ß-D-glucan exohydrolase, a 47.5 kDa glucan 1,3-ß-glucosidase, and two 25 kDa thaumatin-like proteins in C. lawsoniana, and a 25 kDa chitinase in W. mirabilis. Gymnosperm phylogeny is a highly debated topic, particularly following the widespread adoption of molecular phylogenetic analyses which conflict with historical morphological phylogenies. The gymnosperms are a difficult group to classify because of their deep evolutionary history and lack of conservative features. Considering that the pollination drop is a highly conservative feature of gymnosperm reproduction, we propose that analysis of pollination drop protein (PDP) variation could be used as an alternative method to resolve gymnosperm phylogeny. PDP variation was analyzed at three taxonomic levels: genus, family, and gymnosperm clade. Based on variation in SDS-PAGE banding patterns, identified peptides, amino acid sequences, and protein identification, we conclude that PDP variation has a phylogenetic component. Further research is necessary to develop this method into a tool used to predict phylogenetic relationships. Based on protein identifications, there is strong evidence that the pollination drop functions in both pathogen defense and pollen development. The observation of hydrogen peroxide and peroxidase activity in the ovular secretions of J. communis, C. lawsoniana, Pseudotsuga menziesii (Douglas fir), and Larix x marschlinsii (hybrid larch) provided further support for the assumed functions of ovular secretions.en_US
dc.rightsAvailable to the World Wide Weben_US
dc.subject.lcshUVic Subject Index::Sciences and Engineering::Biologyen_US
dc.titleGymnosperm pollination drop proteins and their relation to function and phylogenyen_US


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