Gymnosperm Reproductive Mechanisms

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Conifers such as Douglas-fir, spruce and pines are economically significant species in Canada. Conifers are also one of the four remaining groups of gymnosperms that, from an evolutionary standpoint, are key to the understanding of the origin of flowering plants, the angiosperms. This proposed program of research investigates the events from pollination to fertilization. Seeds often fail because of pollination failure, or because of the consequences of self-pollination; such inbred embryos abort. Gymnosperms are open-pollinated and cannot exclude whatever the wind or insects bring to the ovule. So how do they protect themselves? Can they select their own pollen over foreign pollen? What mechanisms do they have, and what is the biochemical basis for the mechanism? Pollen-ovule interactions include pollen capture by a pollination drop, followed by pollen germination and penetration through the nucellus, ending with the pollen tube's delivery of male gametes into the egg. We will be studying this from a molecular standpoint. Our lab has developed deep expertise in protein analysis of pollination drops. We have discovered that the enzymes protect the ovule during reproduction by killing microbes. We intend to investigate pollination drops in all four groups of gymnosperms (conifers, gnetophytes, cycads, Ginkgo), focusing on proteins (proteome), peptides and polypeptides, sugars, phosphate compounds, and minerals. This will be complemented by an investigation of gene expression in the nucellus. We are searching for genes involved in pollination drop secretions, as well those involved in the formation of barriers to pollen growth, such as megaspore walls. Lastly, we will be investigating the changes in proteome during fertilization. The studies are hypothesis-driven and will engage three PhD students and one Masters student. The impact of this work is practical, leading to deeper understanding of events critical for conifer seed orchard management. The impact is also theoretical, as it is likely alter our understanding of adaptations critical to evolution of the seed habit.