Molecular mechanisms of phloem (bast) fibre development

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The phloem (or bast) fibres of crops such as hemp and flax are remarkably strong and long, with a tensile strength greater than steel, on a per-weight basis. We are interested in learning how flax and hemp develop such long, strong cells, and how the properties of these cells might be optimized to make environmentally friendly textiles and building materials from flax stems, which are now largely treated as a waste product on the approximately 800,000 hectares of Canadian farmland that grows flax for its oil. The length of phloem fibres is affected by an interesting process called intrusive growth, whereby cells grow in between surrounding cells. Although intrusive growth is relatively well characterized in animals, for example, during nerve development, it is less common in plants. Previous work in our laboratory has used techniques called microarray analysis and two-dimensional gel electrophoresis to identify genes associated with fibre development in flax and hemp. The genes we identified are mostly involved in the development of the fibre cell wall, and we are currently characterizing some of these genes in detail. In the proposed research, we would like to look more specifically at the genes that control the length and number of fibre cells that develop in the phloem of flax and hemp. We will again use microarray analysis, as well as various types of mutant screening to identify these genes, and subsequently characterize their function. One immediate outcome of the screening process will be the identification of flax varieties that are easier to harvest, which will reduce the need for environmentally undesirable practices such as straw-burning. In the long term, our research will lead to an improved understanding of how plant cells develop and communicate, and this information will help breeders develop flax and hemp crops with optimized fibre properties for new industries.