Metabolism and regulation of ancient protective biopolymers in the moss, Physcomitrella

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The transition of plants from aquatic to terrestrial environments about 500 million years ago is one of the most important events in the evolution of life on earth. On land, early land plants encountered new challenges, which included surviving exposure to UV irradiation, desiccation and gravity. In order to cope with these challenges, early land plants developed, among other attributes, protective extracellular matrices of sporopollenin, cuticle and lignin. Sporopollenin is the main polymeric constituent of the outer walls of spore and pollen grain and the cuticle is a lipidic outer layer of aerial plant tissues. Lignin, which evolved later, is a class of phenolic polymers that lend rigidity to vascular plant tissue. Bryophytes comprising liverworts, mosses, and hornworts are the simplest and earliest-diverging lineages of land plants, and offer unique windows into the early evolution of land plants. With a complete genome sequence and other research resources, the moss Physcomitrella patens has emerged as a model bryophyte for research on plant evolution. In Physcomitrella, a target gene can efficiently be knocked out, allowing researchers to study the function of the target gene. This research program seeks to understand how the metabolic pathways for the protective materials evolved during early land plant evolution, which is one of the fundamental outstanding questions in plant science. Using multi-faceted, interdisciplinary and hypothesis-based approaches, we will determine how sporopollenin is polymerized during spore maturation and depolymerized during spore germination. We will also study the biosynthesis, metabolism and regulation of the cuticle and lignin-like phenolic compounds that provide the plant with desiccation tolerance and mechanical strength. This research will lead to novel discoveries that are applicable to other plant species, and provide new insights into how the earliest plants successfully adapted on land. Sporopollenin biosynthetic genes are good targets to generate plant male sterility for hybrid seed production and forest/crop control. Being the most robust biopolymer, sporopollenin also has unique applications in biotechnology (biodegradable polymer), medicine (oral vaccination and drug carrier) and wastewater treatment (metal sorbents). Our research may also lead to a new strategy for improving desiccation tolerance in other plants of agricultural importance. This program utilizes diverse research tools and thereby offers training opportunities in different areas of plant science ranging from molecular biology to phytochemistry. HQPs trained in multiple core areas in plant science will contribute to the advancement of science and technology in Canada.