Epigenetic control of early flowering in hyomethylated lines of flax (Linum usitatissimum) induced by 5-azacytidine

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The investigation of mechanisms that control plant growth and development is important because the growth characteristics of a plant determine its potential productivity. During the life cycle of a plant, the transitions between the different developmental phases are regulated by changes in gene expression. One of these transitions is prior to flowering, at the change from vegetative to reproductive growth. Although the physiology of this transition and the genes that ultimately determine the morphology of the flower are fairly well understood, less is known about the genes that initiate and regulate the transition. These genes determine flowering time (age). In the proposed research, early-flowering mutants of flax will be used to investigate the genes that control flowering time and the mechanisms that regulate changes in gene expression at the transition to flowering.  The early-flowering mutants were induced when seeds were treated with an agent that is known to demethylate DNA.  DNA methylation is thought to play a role in the processes that regulate gene activity during plant development.  In the early-flowering lines, the demethylation of the DNA, induced by the treatment, resulted in plants that flower early and are shorter than normal, with fewer leaves, thinner stems, and longer internodes. In each line, at least two independent genes control this early-flowering phenotype and it is thought that the demethylation of sites in the DNA associated with these genes has permanently altered their expression.  The proposed research will provide information about the genes and their roles in controlling flowering time, and also about the role of DNA methylation in regulating gene expression in plants. Early flowering is of agricultural interest because crop plants with short life spans can be planted late and still mature in time for harvest. The economic importance of flax lies in the linseed oil extracted from the seed, which has industrial uses. Canadian-grown flaxseed generates approximately $400 million/year in export revenue.