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

研究控制植物生长发育的机制是很重要的，因为植物的生长特性决定了它的潜在生产力。在植物的生命周期中，不同发育阶段之间的过渡是由基因表达的变化来调节的。其中一个转变发生在开花之前，即从营养生长到生殖生长的转变。虽然这种转变的生理学和最终决定花形态的基因已经被很好地理解，但对启动和调节这种转变的基因知之甚少。这些基因决定开花时间（年龄）。在本研究中，我们将利用亚麻早花突变体来研究控制开花时间的基因以及在开花过渡过程中基因表达变化的调控机制。当种子被一种已知能使DNA去甲基化的药剂处理时，就会诱导出早开花的突变体。DNA甲基化被认为在植物发育过程中调节基因活性的过程中发挥作用。在早花品系中，处理诱导的DNA去甲基化导致植株开花早，比正常植株短，叶片少，茎细，节间长。在每个品系中，至少有两个独立的基因控制着这种早花表型，人们认为，与这些基因相关的DNA中位点的去甲基化已经永久地改变了它们的表达。本研究将进一步揭示植物花期调控基因及其作用，以及DNA甲基化在植物基因表达调控中的作用。早花在农业上是有意义的，因为寿命短的作物可以种植得晚一些，而且还能及时成熟，以便收获。亚麻的经济重要性在于从亚麻籽中提取的亚麻籽油具有工业用途。加拿大种植的亚麻籽每年的出口收入约为4亿美元。

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.